FM Global

Property Loss Prevention Data Sheets 5-32

July 2012
Interim Revision July 2023
Page 1 of 75

DATA CENTERS AND RELATED FACILITIES

Table of Contents
Page

1.0 SCOPE ..................................................................................................................................................... 4

1.1 Hazards ............................................................................................................................................. 4
1.2 Changes ............................................................................................................................................ 4
2.0 LOSS PREVENTION RECOMMENDATIONS ....................................................................................... 4
2.1 Introduction ........................................................................................................................................ 4
2.2 Construction and Location ................................................................................................................. 5
2.2.1 General .................................................................................................................................... 5
2.2.2 Walls ........................................................................................................................................ 6
2.2.3 Doors and Windows ................................................................................................................ 6
2.2.4 Penetrations ............................................................................................................................ 6
2.2.5 Ceilings .................................................................................................................................... 7
2.2.6 Floors ....................................................................................................................................... 7
2.2.7 Cables ..................................................................................................................................... 7
2.2.8 Cable Raceways and Routing Assemblies ............................................................................. 7
2.2.9 Insulation ................................................................................................................................. 7
2.2.10 Earthquake ............................................................................................................................ 7
2.2.11 Windstorm .............................................................................................................................. 8
2.2.12 Flood/Storm Water Runoff ..................................................................................................... 8
2.3 Occupancy ........................................................................................................................................ 9
2.4 Protection ........................................................................................................................................... 9
2.4.1 General .................................................................................................................................... 9
2.4.2 Portable Fire Extinguishers ................................................................................................... 10
2.4.3 Data Processing Equipment Room ....................................................................................... 10
2.4.4 Li-ion Battery Back-up Units for Distributed Power Systems ................................................ 11
2.4.5 Raised Floor or Above-Ceiling Spaces Containing Combustibles ....................................... 13
2.4.6 Detection: Design Specifications ........................................................................................... 13
2.4.7 Suppression: Design Specifications ...................................................................................... 15
2.5 Equipment and Processes .............................................................................................................. 24
2.5.1 Servers, Mainframes, and Supercomputers .......................................................................... 24
2.5.2 Hot/Cold Aisle Containment and Hot Collar Systems ........................................................... 25
2.5.3 Tape Cartridge Storage ......................................................................................................... 28
2.5.4 Mobile/Modular Data Centers .............................................................................................. 29
2.5.5 Network/Broadcast Control Rooms ....................................................................................... 30
2.5.6 Diagnostic Equipment ........................................................................................................... 31
2.5.7 Quantum Computers ............................................................................................................ 32
2.6 Inspection, Testing, and Maintenance ............................................................................................. 32
2.6.1 Facilities ................................................................................................................................. 32
2.6.2 Heating, Ventilation and Air Conditioning (HVAC) ................................................................ 32
2.6.3 Fire Protection ....................................................................................................................... 33
2.6.4 Electrical Power Distribution ................................................................................................ 33
2.7 Human Element ............................................................................................................................... 34
2.7.1 Emergency Response Team (ERT) ...................................................................................... 34
2.7.2 Power Isolation Plan ............................................................................................................. 34
2.7.3 Disaster Recovery Plan ......................................................................................................... 35
2.7.4 Business Continuity Plan ...................................................................................................... 35
2.7.5 Security .................................................................................................................................. 36

©2012-2023 Factory Mutual Insurance Company. All rights reserved. No part of this document may be reproduced,
stored in a retrieval system, or transmitted, in whole or in part, in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without written permission of Factory Mutual Insurance Company.
5-32 Data Centers and Related Facilities
Page 2 FM Global Property Loss Prevention Data Sheets

2.7.6 Flood Emergency Response Plan ........................................................................................ 36

2.7.7 Contingency Plan .................................................................................................................. 36
2.7.8 Service Interruption Plan ....................................................................................................... 38
2.8 Utilities and Support Systems ......................................................................................................... 39
2.8.1 Electrical Distribution System ................................................................................................ 39
2.8.2 Power Isolation of Data Processing Equipment and HVAC Systems .................................. 43
2.8.3 Heating, Ventilation, and Air Conditioning (HVAC) ............................................................... 44
3.0 SUPPORT FOR RECOMMENDATIONS ............................................................................................. 47
3.1 Construction and Location ............................................................................................................. 47
3.1.1 General .................................................................................................................................. 47
3.1.2 Penetrations .......................................................................................................................... 47
3.1.3 Cables ................................................................................................................................... 47
3.1.4 Insulation ............................................................................................................................... 47
3.1.5 Earthquake ............................................................................................................................ 47
3.2 Protection ......................................................................................................................................... 48
3.2.1 General .................................................................................................................................. 48
3.2.2 Data Processing Equipment Rooms ..................................................................................... 49
3.2.3 Raised Floor and Above-Ceiling Areas Containing Cable .................................................... 49
3.2.4 Detection ............................................................................................................................... 49
3.2.5 Suppression ........................................................................................................................... 50
3.3 Equipment and Processes .............................................................................................................. 52
3.3.1 Servers, Mainframes, and Supercomputers .......................................................................... 52
3.3.2 Hot/Cold Aisle Containment and Hot Collar Systems ........................................................... 52
3.3.3 Tape Cartridge Storage ......................................................................................................... 53
3.3.4 Mobile/Modular Data Center ................................................................................................. 53
3.3.5 Diagnostic Equipment ........................................................................................................... 53
3.3.6 Quantum Computers ............................................................................................................. 54
3.4 Utilities ............................................................................................................................................. 54
3.4.1 Electrical Power Distribution .................................................................................................. 54
3.4.2 Electrical Protection for the Data Center .............................................................................. 58
3.4.3 Voltages Used in Various Countries ...................................................................................... 59
3.4.4 Power-Down of Data Processing Equipment and HVAC Systems ....................................... 60
3.4.5 Heating, Ventilation, and Air Conditioning (HVAC) ............................................................... 61
3.4.6 Uptime Institute Tier Classification ........................................................................................ 61
3.5 Loss History ..................................................................................................................................... 62
3.5.1 NFPA ..................................................................................................................................... 62
4.0 REFERENCES ..................................................................................................................................... 63
4.1 FM Global ........................................................................................................................................ 63
4.1.1 FM Approvals ........................................................................................................................ 63
4.2 Other Standards ............................................................................................................................ 64
APPENDIX A GLOSSARY OF TERMS ...................................................................................................... 65
APPENDIX B DOCUMENT REVISION HISTORY ..................................................................................... 68
APPENDIX C PERFORMANCE TEST PROCEDURES FOR VEWFD SYSTEMS .................................... 72
C1. Objectives ....................................................................................................................................... 72
C2. Heated Wire Test ............................................................................................................................ 72
APPENDIX D CLEAN AGENTS .................................................................................................................. 74
APPENDIX E BIBLIOGRAPHY .................................................................................................................. 74

List of Figures
Fig. 2.1. Conceptual layout of data center facility ......................................................................................... 5
Fig. 2.4.4.1. Typical configuration of Battery Back-up Units in Distributed Power System ........................ 12
Fig. 2.4.4.2. Vertical barrier location ............................................................................................................. 12
Fig. 2.4.6.6.1. Very early warning fire detection (VEWFD); air-aspirating type ........................................... 14
Fig. 2.4.7.1.5.D. Schematic of preaction valve with test discharge line ...................................................... 19
Fig. 2.5.1.1.2. Typical server cabinet and rack arrangement ...................................................................... 24
Fig. 2.5.2.11.A. Conceptual view of cold aisle containment system ........................................................... 27
Fig. 2.5.2.11.B. Conceptual view of hot aisle containment system ............................................................. 27
Fig. 2.5.2.11.C. Conceptual view of hot collar containment system ............................................................ 28

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 3

Fig. 2.5.2.11.D. Conceptual view of hot/cold aisle with horizontal air flow without a raised floor ............... 28
Fig. 2.8.1.2.2. Utility Main Switchgear .......................................................................................................... 40
Fig. 2.8.1.4.3.1. Distributed Redundant Power ............................................................................................ 42
Fig. 3.4.1.1.a. Electrical power distribution for a data center (Redundant Distribution) .............................. 55
Fig. 3.4.1.1.b. Electrical power distribution for a data center (PDU Pairing) ............................................... 56
Fig. 3.4.1.1.c. Uninterruptible power system for a data center) ................................................................... 57

List of Tables
Table 2.4.7.1.2. Sprinkler System Operation Sequence .............................................................................. 16
Table 3.4.3. Medium and Low Voltages Used in Various Countries ............................................................ 59
Table 3.4.6. Tier Requirements Summary .................................................................................................... 62
Table C-2. Heated-Wire Test Parameters ..................................................................................................... 72
Table D-1. Design Concentrations for Clean Agents ................................................................................... 74
Table D-2. Design Concentrations for Clean Agents with an Energized Electrical Hazard ......................... 74

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 4 FM Global Property Loss Prevention Data Sheets

1.0 SCOPE
This data sheet contains property loss prevention recommendations for data centers and their critical systems
and equipment. This data sheet also identifies the hazards associated with these facilities and recommends
risk-mitigation solutions from a property protection and business continuity perspective.
Related facilities covered in this data sheet include network control rooms, broadcast equipment and
diagnostic equipment. Where the term “data center” is used in this document, facilities that have similar
electronic equipment are also intended.
This data sheet does not cover the following:
• Telecommunication and broadcast facilities that use direct current (DC) power; refer to Data Sheet
5-14, Telecommunications.
• Motor control centers and switchgear rooms; refer to Data Sheet 5-19, Switchgear and Circuit
Breakers.
• Process control rooms, refer to Data Sheet 7-110, Industrial Control Systems.

1.1 Hazards
The main hazard associated with data centers and similar facilities is damage to sensitive electronic
equipment caused by smoke, liquid from a variety of sources, and natural hazard exposures.
Fire-related hazards include energized equipment and cabling, power supply areas (backup generator fuel
systems and UPS batteries) and storage of spare cables (plastics) and other combustible materials. Fire
involving energized equipment and cabling will grow slowly, release large amounts of smoke, and cannot
be completely extinguished until the power is shut off.
Hazards to the functional operation of a data center include lack of power to data processing equipment
support systems (e.g., HVAC).

1.2 Changes
July 2023. Interim revision. Made editorial change to Table D-2 of Class C design concentration for
FK-5-1-12. Revised the minimum design concentration percentage to include the proper safety factor based
upon the Class A minimum extinguishment concentration.

2.0 LOSS PREVENTION RECOMMENDATIONS

2.1 Introduction
A data center consists of equipment room(s), utilities, and support infrastructure. See Figure 2.1 for a
conceptual layout.
The following represents FM Global’s loss prevention recommendations for new data centers and related
facilities. Particular attention should be given to using noncombustible construction materials, plenum-rated
wires and cables, plenum-rated raceways and routing assemblies, non-fire-propagating hot/cold aisle
containment materials, and noncombustible filters and insulation. Fire detection and suppression options are
also provided.
Use FM Approved equipment, materials, and services whenever they are applicable and available. For a
list of products and services that are FM Approved, see the Approval Guide, an online resource of FM
Approvals.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 5

CRAC CRAC CRAC

Tape
media
storage

Data center equipment room

Control
room
CRAC CRAC CRAC

Storage & Mechanical room

Offices maintenance
(air handlers, chillers,
electrical panels, etc.)

Lobby & security Battery UPS Diesel generators

room and/or rotary UPS

Fig. 2.1. Conceptual layout of data center facility

2.2 Construction and Location

2.2.1 General
2.2.1.1 Construct data centers of noncombustible materials. Plastic materials, including those of fire-retardant
composition, can produce large quantities of smoke and should not be used.
2.2.1.2 If plastic materials are used, provide materials either FM Approved or specification-tested to:
A. FM Approval Standard 4882, Class 1 Interior Wall and Ceiling Materials or Systems for Smoke Sensitive
Occupancies
B. FM Approval Standard 4884, Panels Used in Data Processing Center Hot and Cold Aisle Containment
Systems
C. FM Approval Standard 4910, Cleanroom Materials Flammability Test Protocol, (FM4910 plastics).
Specification-tested products are listed in the Building Materials section of the Approval Guide, an online
resource of FM Approvals.
2.2.1.3 Protect data centers against external fire exposure. Do not allow combustible material to expose
the building or the air intake(s) for the building. Provide blank masonry walls or other suitable protection when
there is an unfavorable exposure or the potential for vandalism from outside the building (refer to Data Sheet
1-20, Protection Against Exterior Fire Exposure).
2.2.1.3.1 Protect data centers from exterior exposure from:
• Transformers in accordance with Data Sheet 5-4, Transformers.
• Diesel generators in accordance with Data Sheet 5-23, Design and Protection For Emergency and
Standby Power Systems.
2.2.1.4 For high rise data centers, construct the building in accordance with Data Sheet 1-3, High-Rise
Buildings.
2.2.1.5 For multi-story (non-high rise) data centers, construct the building in accordance with Data Sheet
1-3, High Rise Buildings, for the following:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 6 FM Global Property Loss Prevention Data Sheets

• Fire resistance of building elements

• Protection of openings in floors
• Protection of penetrations
2.2.1.5.1 Do not locate data centers in multistory buildings that have inadequately sprinklered or unprotected
areas of the building.
2.2.1.6 Provide prevention and mitigation associated with a liquid release and the potential damage in
accordance with Data Sheet 1-24, Protection Against Liquid Damage.
2.2.1.7 Locate data centers so they are not exposed to damage from any hazardous process, storage,
corrosive or ignitable liquid or vapor, industrial pollutants, or mechanical equipment such as overhead cranes.
2.2.1.8 Provide supervision of the data center to prevent unauthorized access to the premises and assets
in accordance with Data Sheet 9-1, Supervision of Property.

2.2.2 Walls
2.2.2.1 Provide one-hour fire-rated interior walls, partitions, and floors in accordance with Data Sheet 1-21,
Fire Resistance of Building Assemblies, for all of the following:
• data processing equipment rooms
• battery power rooms, uninterruptible power supply (UPS) rooms
• network/fiber optic rooms
2.2.2.2 Provide fire-rated interior walls, partitions, and floors for power equipment rooms (standby generator
and AC power) in accordance with Data Sheet 5-23, Design and Protection for Emergency and Standby
Power Systems.
2.2.2.3 Have fire-rated interior walls built from the structural floor of the room to the structural floor above
(or to the roof).
2.2.2.4 Provide openings in maximum foreseeable loss (MFL) fire walls, fire partitions, and floors in
accordance with Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers.
2.2.2.5 Use the limiting factors in Data Sheet 1-42, MFL Limiting Factors, to limit the maximum exposure
from property loss and business interruption. Provide particular consideration of these recommendations to
campus style data center locations having multiple data center buildings on the premises of the campus.

2.2.3 Doors and Windows

2.2.3.1 Minimize interior windows and doors to the data processing equipment room. For essential interior
windows and doors, use tempered or wired glass for windows and minimum 3/4 hour fire-rated doors.
2.2.3.2 If doors are held open intermittently or permanently, provide an electromechanical or electromagnetic
holding mechanism interlocked to close the door on smoke detector actuation.

2.2.4 Penetrations
2.2.4.1 Seal openings in fire-rated floors and walls through which ducts, pipes, wires, and cables pass using
an FM Approved or listed penetration seal with a fire-resistance rating equivalent to the rating of the wall
or floor.
2.2.4.2 Provide a leakage-rated penetration seal with a rating as low as possible, but not exceeding
7 ft3/min/ft2 (2.1 m3/min/m2) in addition to the fire-resistance rating for equipment room penetrations (see
Section 3.1.2).
2.2.4.3 When new construction or modifications are in progress, install temporary FM Approved fire-stop
penetration seals (e.g., bricks, plugs, cushions) for protection when work is stopped at night and during
weekends.
2.2.4.4 Seal openings in fire-rated floors and walls through which HVAC duct(s) pass with an FM Approved
fire damper that has a fire-resistance rating equivalent to the rating of the wall or floor.
2.2.4.5 Provide smooth or protected electrical cable openings in floors (e.g., grommets, cable glands) to
prevent damage to the cables.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 7

2.2.5 Ceilings
2.2.5.1 Construct suspended ceilings of Class I materials; see Data Sheet 1-12, Ceilings and Concealed
Spaces.
2.2.5.2 Limit the maximum height of ceilings in data centers to 30 ft (9 m). (See Section 2.4.7.1.3 and Section
3.2.5.1.)

2.2.6 Floors
2.2.6.1 Construct floors, raised floors, and structural supporting members for raised floors of noncombustible
materials.

2.2.7 Cables
2.2.7.1 Provide all grouped cables and cable trays (power and data) in accordance with Data Sheet 5-31,
Cable and Bus Bars in addition to the following recommendations in this section.
2.2.7.2 Use communication and data cable (e.g., coaxial and fiber optic) and power cables that meet one
of the following criteria:
A. FM Approved Class Number 3972; Group 1 or Group 1-4910
B. Plenum rated cable listed to Underwriters Laboratories (UL) Standard 910
C. Cable that has maximum flame spread distance of 5 ft (1.5m) or less tested in accordance with NFPA
262.
2.2.7.3 When communication, data and power cables cannot be provided in accordance with Section 2.2.7.2,
provide protection for propagating and combustible materials in accordance with Section 2.4.7.1, Section
2.4.7.2 and Section 2.4.7.3.
2.2.7.4 Separate power cables from communication/data cables by keeping the power cables in a separate
cable tray/raceway or routing assembly.
2.2.7.5 Remove abandoned or routine spare cables that are not in service and are not intended for future
service.

2.2.8 Cable Raceways and Routing Assemblies

2.2.8.1 Use cable raceways and routing assemblies made of noncombustible materials whenever possible.
2.2.8.2 When cable raceway and routing assemblies must be constructed of plastic, use one of the following:
A. FM Approvals 4910 specification-tested plastics listed in the Building Materials section of the Approval
Guide (FM4910 plastics), or
B. Plenum-rated plastic raceways listed to Underwriters Laboratory (UL) Standard 2024.
2.2.8.3 Do not use cable raceways, routing assemblies or junction boxes constructed of polyvinyl chloride
(PVC) material for power cables.

2.2.9 Insulation
2.2.9.1 Provide building insulation and elastomeric materials installed on the building and on the floor beneath
a raised floor in accordance with Data Sheet 1-57, Plastics in Construction.
2.2.9.2 Provide pipes and ducts using insulation with one of the following:
A. Noncombustible insulating materials (e.g., foil-wrapped fiberglass or mineral fiber wool), or
B. FM Approved insulation (Approved to FM Approvals Standard 4924)

2.2.10 Earthquake
If the facility is located in FM Global 50-year through 500-year earthquake zones as defined in Data Sheet
1-2, Earthquakes, adhere to the recommendations in this section.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 8 FM Global Property Loss Prevention Data Sheets

2.2.10.1 For new facilities (and for existing facilities at significant risk), have a seismic risk analysis conducted
by a consulting firm specializing in earthquake design and evaluation. Consider all aspects of facility
construction design, as well as process and building service equipment for local code compliance and
applicable recommendations of Data Sheet 1-2, Earthquakes, and components and systems in the scope
of Section 2.2.10.
2.2.10.2 Use construction and protection components that are listed in the Approval Guide for seismic
protection whenever possible.
2.2.10.3 Provide seismic protection adequate to resist the forces specified in Data Sheet 1-2, Earthquakes,
or the local building code, whichever is more stringent, for the items identified in Sections 2.2.10.4 through
2.2.10.7.
2.2.10.4 Provide seismic bracing and anchoring of fire protection sprinkler and water-mist systems per Data
Sheet 2-8, Earthquake Protection for Water-Based Fire Protection Systems.
A. Provide bracing for special fire protection systems (e.g., clean agents) per Data Sheet 2-8, Earthquake
Protection for Water-Based Fire Protection Systems, and Data Sheet 1-2, Earthquakes.
B. For both water-based and clean agent fire extinguishing systems, brace and anchor all components,
including piping, pumps, and cylinder banks.
2.2.10.5 Provide seismic anchoring and bracing for data processing equipment (e.g., server racks,
mainframes, automated tape libraries).
2.2.10.5.1 Seismic isolation (e.g., free-rolling-base isolator pads under servers) of electronic equipment is
an acceptable alternative to anchoring if a detailed seismic analysis is provided for the specific location.
2.2.10.6 Provide seismic bracing for access (raised) floor systems, including mechanical anchors (e.g., bolts)
at the base of access floor support pedestals to the structural floor, and separate bracing to resist lateral
movement of the access floor (e.g., angled cross bracing from the structural floor to the access floor supports).
2.2.10.7 Provide seismic bracing and support of data processing equipment and support systems (with the
performance goal of maintaining uninterrupted data equipment system operations during and after an
earthquake), including but not limited to, the following:
A. HVAC: air handling units, liquid piping (e.g., chilled water, condensing water, condensate drains,
refrigerant), cooling towers, pumps, etc.
B. Plumbing and process piping conveying liquids (e.g., potable water, roof drains, pure water, etc.) located
in or above data processing equipment spaces and that cannot be relocated.
C. Electrical power and data raceways: single conduit 2-1/2 in. (6.35 cm) or greater diameter; cable
raceways, cable trays, and conduit racks where the total load is more than l0 lb/ft (15 kg/m). No additional
seismic protection is needed on these items if they are supported by hangers 12 in. (0.3 m) or less in
length.
D. Uninterruptible power systems (UPS), including restraint of battery racks and batteries to the racks.
E. Emergency power generation systems: generators, fuel tanks, fuel piping.
F. Electrical power systems: switchgear, motor control centers, transformers, bus bars.

2.2.11 Windstorm
2.2.11.1 Design buildings, roof-mounted equipment, and ground-mounted equipment for wind forces in
accordance with Data Sheet 1-28, Wind Design, and Data Sheet 1-29, Roof Deck Securement and Above-
Deck Roof Components. Design towers in accordance with Data Sheet 1-8, Antenna Towers and Signs.
2.2.11.2 Minimize the number of exterior windows and doors to the data center. When required, provide them
in accordance with Data Sheet 1-28, Wind Design.

2.2.12 Flood/Storm Water Runoff

2.2.12.1 Select a building site that is above the predicted 0.2% annual exceedance (500-year) flood elevation
and includes 1 to 2 ft (0.3 to 0.6 m) of freeboard. Ensure the building site is at least 500 ft (152 m) from
direct wave impacts and/or high flood-flow velocities (i.e., above 7 fps [2 m/s]). (See Data Sheet 1-40, Flood.)

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 9

2.2.12.2 Protect data centers, critical systems, and equipment of the facility and related facilities against
storm water runoff in accordance with Data Sheet 1-40, Flood.
2.2.12.3 Provide water-removal capability for all below-grade areas subject to flooding from storm water runoff
or sewer backup.
2.2.12.4 Provide automatic-starting sump pumps with an alarm to a constantly attended area.
2.2.12.5 Connect electric-powered sump pumps to the backup power supply.

2.3 Occupancy
2.3.1 Locate new data processing equipment with packaging awaiting installation in storage and staging
areas separate from data processing equipment rooms (i.e., where fire involving the storage will not expose
critical equipment).
2.3.2 Do not store or stage combustible materials in the data processing equipment room.
2.3.3 Remove cartons and packaging materials from in-process equipment in the data processing equipment
room. Metal containers that use combustible packaging materials to protect in-process equipment are
tolerable.
2.3.4 Do not store combustible materials in electrical or mechanical equipment rooms.
2.3.5 Protect storage areas in accordance with Data Sheet 8-9, Storage of Class 1,2,3,4 and Plastic
Commodities.

2.4 Protection

2.4.1 General
2.4.1.1 Provide automatic sprinkler protection throughout all building spaces associated with this occupancy
for the appropriate hazard classification in accordance with Data Sheet 3-26, Fire Protection Water Demand
For Nonstorage Sprinklered Properties, and/or the hazard-specific data sheet, in addition to the
recommendations in this section.
2.4.1.2 Install fire detection in areas that are adjacent to the data processing equipment room and in rooms
containing systems or equipment critical to the continued operation of the data processing facility (e.g.,
offices, hallways, storage areas/rooms, loading docks).
2.4.1.3 Install fire detection in accordance with Data Sheet 5-48, Automatic Fire Detection.
2.4.1.3.1 Limit cooling air velocities in data processing equipment rooms and any utility rooms upon activation
of the pre-alarm for the FM Approved Very Early Warning Fire Detection (VEWFD) system, reference section
2.4.6, to a maximum of 5 ft/sec (1.5 m/sec) in accordance with Section 2.8.3.B.4 in order to provide adequate
fire detection (reference Section 2.4.6) and protection (reference section 2.4.3.1).
2.4.1.4 Do not install automatically operated smoke exhaust systems in the data processing equipment rooms.
2.4.1.4.1 Where an automatic operation is required by local code, interlock the activation of the smoke
exhaust system with the alarm for operation of the sprinkler system. Do not interlock the smoke exhaust
system for activation with the fire detection system.
2.4.1.4 Install fire alarm systems in accordance with Data Sheet 5-40, Fire Alarm Systems.
2.4.1.5 Establish a formal manual power isolation plan in accordance with Section 2.7.2 for all locations
regardless of the fire protection provided within the data processing equipment room(s).
A. Make the goal of the manual power isolation plan to de-energize all electrical power to the data
processing equipment and dedicated heating, ventilation, and air conditioning (HVAC) systems in the data
processing equipment room or designated zones(s), except power to lighting, in the event of a smoke
detection alarm.
B. Focus the manual power isolation plan on disconnecting power to affected energized sources on as
local a level as possible based on current conditions, but still be capable of powering down an entire room
if necessary.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 10 FM Global Property Loss Prevention Data Sheets

2.4.1.6 Do not use aerosol generator fire extinguishing system units for the protection of the data center,
related areas, or electronic equipment.
2.4.1.7 Do not use oxygen-reduction systems for the protection of the data center, related areas, data
processing equipment, or electronic equipment unless the recommendations in Data Sheet 4-13, Oxygen
Reduction Systems, can be fully applied in addition to the recommendations in this section.
2.4.1.7.1 Do not provide oxygen-reduction systems for protection of the data center, related areas, data
processing equipment, or electronic equipment using Li-ion batteries.
2.4.1.7.2 Provide the oxygen concentration design point that uses the measured oxygen concentration listed
in Data Sheet 4-13 for the data processing equipment room fire related hazard as follows:
A. Cables – Commodity; Uncartoned (UUP, UEP)
B. All other hazards – Commodity; Cartoned (Class 3, CUP, and CEP)
2.4.1.7.3 Maintain air flow of the HVAC system for the cooling of data server equipment in the data processing
equipment room in the design of the oxygen reduction system.
2.4.1.7.4 Provide personnel access to the protected area in accordance with local codes for the application
of oxygen reduction systems.

2.4.2 Portable Fire Extinguishers

2.4.2.1 For energized electrical hazards, provide at least one carbon dioxide or clean agent portable fire
extinguisher listed to protect electronic equipment in accordance with Data Sheet 4-5, Portable Fire
Extinguishers.
A. Use a maximum floor area of 3,000 ft2 (280 m2) per portable fire extinguisher.
B. Use a maximum travel distance of 75 ft (23 m) between each portable fire extinguisher.
2.4.2.2 For ordinary combustible materials and energized electrical fires, provide portable fire extinguishers
of the type or combination of types that are suitable per with Data Sheet 4-5, Portable Fire Extinguishers,
when both hazards are present.
A. Use a minimum rating of 2-A (NFPA 10 rating and classification).
B. Use a maximum floor area of 3,000 ft2 (280 m2) per portable fire extinguisher with a 2-A rating, and
1,500 ft2 (140 m2) per each additional “A” rating to a maximum of 11,250 ft2 (1045 m2).
C. Use a maximum travel distance of 75 ft (23 m) between each portable fire extinguisher.
2.4.2.3 Do not use dry chemical fire extinguishers in data processing equipment rooms with data processing
equipment or electronic equipment.
2.4.2.4 Locate a portable fire extinguisher at each entrance of the data processing equipment room. Locate
additional fire extinguishers in the data processing equipment room based upon the above recommendations
for area per extinguisher and travel distance.
2.4.2.5 Locate a sign adjacent to (or verify the adequacy of the labeling on) the portable fire extinguisher
to identify the type of fire it is intended to extinguish.
2.4.2.6 Provide training to staff working in the area on the selection and safe use of portable fire extinguishers.

2.4.3 Data Processing Equipment Room

2.4.3.1 Provide FM Approved very early warning fire detection (VEWFD; see Appendix A, Glossary of Terms)
in the data processing equipment room and HVAC return air systems. See Data Sheet 5-48, Automatic Fire
Detection.
2.4.3.2 Where an enhanced level of detection is desired for critical business operations and/or in support
of manual power isolation, install VEWFD directly in equipment racks or cabinets.
2.4.3.3 Install VEWFD in accordance with Section 2.4.6.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 11

2.4.3.4 Provide one of the following fire protection systems to protect the data processing equipment room
structure when there are no distributed Li-ion battery back-up units in the server racks. For data processing
equipment rooms with distributed Li-ion battery back-up units in sever racks refer to Section 2.4.4.
A. An automatic wet or preaction sprinkler system throughout the data center, designed in accordance
with Section 2.4.7.1.
B. An automatic FM Approved water mist system listed specifically for protection of data processing
equipment rooms, designed in accordance with Section 2.4.7.2.
C. An FM Approved clean agent fire extinguishing system designed in accordance with Section 2.4.7.3,
if all of the following conditions are met:
1. Automatic power-down is provided to the room and equipment (except to emergency lighting) upon
smoke detection by VEWFD.
2. Construction is noncombustible.
3. Equipment enclosures are constructed of metal.
4. There is scant use of paper and other combustibles in the room. (Scant in this context means a
quantity and distribution of combustibles that, in a worst-case fire scenario, could be successfully
extinguished using only one portable fire extinguisher.)
5. There is no storage of packing materials or plastic cassettes within the room. Note: This includes
all combustible media (e.g., tape reels).
6. Shutdown and/or damper of ventilation systems that use return or make-up air is provided.

2.4.4 Li-ion Battery Back-up Units for Distributed Power Systems

2.4.4.1 Where Li-ion battery back-up units (BBU) are installed in a server rack as a distributed power system,
the recommendations in this section are to be applied if the following conditions exist:
A. Maximum power capacity of 20 kWh per server rack as a distributed power configuration. (Refer to
Section 3.4.1.2 for calculating power capacity.)
B. No more than two shelves containing BBU modules located together in the same area of the rack.
(See Figure 2.4.4.1 for typical configuration.)
C. Aisle spacing between server rows is a minimum of 4 ft (1.2 m).
D. Ceiling height is a maximum 30 ft (9 m). (Refer to Section 3.2.5.1.)
E. No limitation on the building/room size (area in ft2/m2).
2.4.4.1.1 Server racks with distributed Li-ion Battery Back-up Units (BBU) exceeding the maximum capacity
of 20 kWh per rack should be considered Energy Storage Systems (ESS); and the recommendations
identified in DS 5-33, Energy Storage Systems, should be followed.
2.4.4.2 Provide vertical barriers in all server rack rows where Li-ion distributed power systems are used or
expected to be used, regardless of the power capacity. Provide vertical barriers as follows (see Figure 2.4.4.2):
2.4.4.2.1 Locate after every third rack along the entire length of server rows
2.4.4.2.2 Use a minimum 20-gauge (0.9 mm) solid sheet metal for the vertical barriers on the side of every
third rack to limit the fire spread.
2.4.4.2.3 Completely cover the side of the server rack with the barrier to fit the rack side profile.
2.4.4.2.4 Install in a way that will not reduce the effectiveness of the hot/cold aisle air flow cooling aisle
arrangement (kept to the side frame profile of the server racks).
2.4.4.3 Provide one of the following automatic protection options throughout all building areas associated
with this hazard:
A. Use FM Approved quick-response (QR) sprinklers in accordance with Data Sheet 2-0, Installation
Guidelines for Automatic Sprinklers, and the following specifications:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 12 FM Global Property Loss Prevention Data Sheets

AC Power AC Power
Zone 1 Zone 2

PDU PDU
Rack Switch(es)

Server & Storage

Power
Zone 1 Power Shelf

87 in. (2210 mm)

Server & Storage

Server & Storage

Power
Zone 2
Power Shelf

Server & Storage

24 in. (610 mm)

Fig. 2.4.4.1. Typical configuration of Battery Back-up Units in Distributed Power System

20 Gauge Metal Barrier 20 Gauge Metal Barrier 20 Gauge Metal Barrier

Server Racks Server Racks Server Racks

Minimum aisle space 4ft (1.2m)

Server Racks Server Racks Server Racks

20 Gauge Metal Barrier 20 Gauge Metal Barrier 20 Gauge Metal Barrier

20 Gauge = 0.9mm

Fig. 2.4.4.2. Vertical barrier location

1. Minimum density 0.2 gpm/ft2 (8 mm/min). Sprinkler deflector distance from the ceiling (min: 1.75
in. [44 mm]; max: 4 in. [100 mm]).
2. For wet, non-interlock or single interlock preaction systems, use a demand area of 2500 ft2 (230
m2).
3. For double interlock preaction systems, use a demand area of 3,500 ft2 (320 m2).
4. Provide a maximum linear spacing of 12 ft (3.6 m) and area spacing of 144 ft2 (13.4 m2), or a reduced
spacing and area for clearance from obstructions, in accordance with Data Sheet 2-0, Installation
Guidance for Automatic Sprinklers.
B. Use FM Approved automatic water mist systems with the following specifications:
1. Approved for protection of non-storage, Hazard Category (HC-2) occupancies

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 13

2. Provided in accordance with Sections 2.4.7.2.2 through 2.4.7.2.9

2.4.4.3 Provide a hose allowance of 250 gpm (950 L/min).
2.4.4.4 Provide a water supply duration of 60 minutes.
2.4.4.5 Do not use clean agent fire extinguishing systems to provide protection. (See Section 3.4.1.2.)

2.4.5 Raised Floor or Above-Ceiling Spaces Containing Combustibles

2.4.5.1 Provide FM Approved very early warning fire detection (VEWFD) below raised floors and in
above-ceiling spaces that contain cables in accordance with Section 2.4.6.
2.4.5.2 Detection systems below the raised floor space may be omitted under either of the following
conditions:
A. If only FM Approved Group 1, Group 1-4910, or UL-listed plenum-rated cables are present (refer to
Data Sheet 5-31, Cables and Bus Bars).
B. If VEWFD detection is provided at the air return for forced air re-circulated from below the raised floor
into the room.
2.4.5.3 If an intelligent VEWFD spot-type smoke detector is used below a raised floor, ensure it is mounted
in the proper orientation as indicated in its FM Approval listing.
2.4.5.4 Protect grouped cables and cable trays in accordance with Data Sheet 5-31, Cable and Bus Bars.
2.4.5.5 Fire protection for cables is not needed when the types of cables identified in Section 2.2.7.2 are used.
2.4.5.6 Do not install exposed combustible elastomeric materials beneath raised floors.
2.4.5.6.1 When installing combustible elastomeric materials beneath a raised floor is unavoidable, protect
elastomeric materials installed on the floor and supports in accordance with the relevant recommendations
in Data Sheet 1-57, Plastics in Construction.
2.4.5.7 Provide an automatic fire protection system in the following places:
A. Below noncombustible raised floors or in above-ceiling spaces when propagating cables are present.
B. Below a raised floor area when it is made of combustible construction.
2.4.5.8 Provide one of the following fire protection systems:
A. Automatic extended coverage (EC) nonstorage sprinkler protection designed in accordance with Section
2.4.7.1.3 for protection of combustibles above a ceiling space or below a noncombustible raised floor.
B. An FM Approved inert gas clean agent fire extinguishing system designed in accordance with Section
2.4.7.3 for protection of combustibles below a raised floor.
C. A halocarbon clean agent fire extinguishing system, but only if the data processing equipment room
is simultaneously protected by the same halocarbon clean agent.
D. An FM Approved water mist system specifically listed for raised floor protection designed in accordance
with Section 2.4.7.2.
2.4.5.9 Actuate the fire protection system by smoke detection in accordance with Section 2.4.6.
2.4.5.10 Provide a ready means of access in proximity to the detectors, sprinklers, and fire extinguishing
system nozzles in the raised floor or above-ceiling space for inspection and maintenance.

2.4.6 Detection: Design Specifications

Install fire detection per Data Sheet 5-48, Automatic Fire Detection, in conjunction with the following
recommendations.
2.4.6.1 For data processing equipment areas/rooms, provide FM Approved VEWFD systems installed in
accordance with the recommendations in this section and the manufacturers instructions.
2.4.6.2 Use one of the following FM Approved VEWFD systems as appropriate for the characteristics of the
occupancy:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 14 FM Global Property Loss Prevention Data Sheets

A. Air aspirating
B. Intelligent high-sensitivity spot detection; photoelectric type
2.4.6.3 Transmit fire alarms to a central supervisory station or other constantly attended location.
2.4.6.4 Transmit local alarms from the protected area, e.g., alert, pre-alarm and alarm condition, to a
constantly attended location.
2.4.6.5 Install the fire alarm control panel for fire detection in accordance with Data Sheet 5-40, Fire Alarm
Systems.
2.4.6.6 Air Aspirating Detection
2.4.6.6.1 Install sensors or ports to monitor the return air. (See Figure 2.4.6.6.1.)
A. Locate sensors or ports at the return air inlet of each HVAC unit and/or at the interface of the exhaust
air plenum (see Section 3.2.4).
B. Locate sensors or ports so each covers an area no greater than 4 ft2 (0.4 m2) of the return opening.

SSR METHOD
86.062 VERTICALLY
SHEAR 30º
ROTATE -30º

AIR HANDLING
UNIT

AIR SAMPLING
DETECTORS

DATA EQUIPMENT

EXHAUST
AIR PLENUM

EXHAUST AIR VENT

DETECTION FOR EXHAUST AIR

AIR SAMPLING GRID

DETECTION FOR AHU INTAKE

Fig. 2.4.6.6.1. Very early warning fire detection (VEWFD); air-aspirating type

2.4.6.6.2 Where a single level of detection is used, install a sensor or port in an area no larger than
200 ft2 (18.6 m2). (See Figure 2.4.6.6.1)
A. The sensors or ports do not need to be located in the center of the bay.
B. Do not locate sensors or ports within 3 ft (0.9 m) of HVAC supply outlets unless detecting for failure
originating with the HVAC unit (e.g., burning belt, bearing).
2.4.6.6.3 If two levels of detection are used, install a sensor or port in an area no larger than 400 ft2
(37.2 m2) for both levels.
2.4.6.6.4 Provide two levels of detection where cable trays impede the flow of smoke to the ceiling.
A. Locate one level of detection below the cable trays and one level at the ceiling.
B. Stagger the sensors or ports in an area no larger than 200 ft2 (18.6 m2) between each level.
2.4.6.6.5 For air-sampling VEWFD, do not exceed a transport time of 60 seconds from the most remote port
to the detection unit.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 15

2.4.6.7 Intelligent High-Sensitivity Spot Smoke Detection

2.4.6.7.1 Use FM Approved intelligent high-sensitivity spot smoke detectors of the photoelectric type when
cooling air velocities do not exceed either 5 ft/s (1.5 m/s) or 60 air changes per hour.
2.4.6.7.2 Install FM Approved intelligent high-sensitivity spot smoke detectors to monitor the return air.
A. Locate the spot detectors at the return air inlet of each HVAC unit and/or at the interface of the exhaust
air plenum (see Section 3.2.4).
B. Locate the spot detectors so each covers an area no greater than 4 ft2 (0.4 m2) of the return opening.
2.4.6.7.3 Provide at least two FM Approved intelligent high-sensitivity spot smoke detectors in each protected
space or zone for initiation of the protection system.
2.4.6.7.4 Install the FM Approved intelligent high-sensitivity spot smoke detectors in accordance with the
manufacturers specification for spacing based on the air movement (e.g., air changes per minute/hour in the
protected space or zone).
2.4.6.8 Provide minimum sensitivity settings above the ambient airborne levels and consider the impact of
functional devices on the HVAC system (e.g., outside air economizers with or without dampers) for alert,
pre-alarm and alarm conditions.
2.4.6.8.1 Where high air velocities (exceeding either 5 ft/s (1.5 m/s) or 60 air changes per hour) are required
for proper cooling, provide an interlock to reduce the air flow velocity upon fire detection in accordance with
Section 2.8.3.B.
2.4.6.9 Provide an annunciator panel at the fire alarm control panel arranged to indicate pre-alarm and alarm
signals from VEWFD system.
2.4.6.9.1 Conduct smoke tests (see Appendix C) when the VEWFD system is installed to verify smoke
detectors are properly located with regard to air flow and velocity within the protected area, including
ventilation and stratification within the protected area.

2.4.6.10 Portable Detection

2.4.6.10.1 Supplement fixed smoke detection with portable handheld detection devices (e.g., aerosol monitors
and thermal imaging devices) to assist in locating the origin of an alarm within a detection zone

2.4.7 Suppression: Design Specifications

The reliability of a protection system is a function of the complexity of the system and the number of interacting
components for its operation.
An automatic sprinkler system or water mist system may be used to protect a data processing equipment
room with a forced air ventilation cooling system with a maximum nominal upward velocity through perforated
floor openings, and a horizontal airflow of maximum 5 ft/sec (1.5 m/sec).
Where higher air velocities are required for proper cooling, provide an interlock to reduce the air flow velocity
upon fire detection in accordance with Section 2.8.3.B.

2.4.7.1 Automatic Sprinklers

2.4.7.1.1 Install sprinkler systems in accordance with Data Sheet 2-0, Installation Guidelines for Automatic
Sprinklers, the equipment manufacturer’s manual and the recommendations in this section of Data Sheet
5-32.
2.4.7.1.2 Provide one of the following types of automatic sprinkler protection, listed in order of preference
based on reliability and maintenance (i.e., annual trip test; refer to Section 3.2.5.1):
A. Wet system
B. Non-interlocked preaction system
C. Single-interlocked preaction system
D. Double-interlocked system

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 16 FM Global Property Loss Prevention Data Sheets

The type of automatic sprinkler system (reference Table 2.4.7.1.2) provided should consider the impact of
a delay in water being applied to the fire and ability to conduct maintenance. In particular, the extended delay
from a double-interlock preaction system requires both smoke detection and sprinkler activation which can
negatively impact control of the fire and the available water supply. In addition, the complexity of the preaction
valve trim decreases the availability of the fire protection system.

Table 2.4.7.1.2. Sprinkler System Operation Sequence

Sprinkler System
Type Detection Activation Function(Note 1) Sprinkler Activation Supervision(Note 2)
Wet Not Applicable N/A Water discharges Not Applicable
Non-interlocked Water fills piping Or Water fills piping and Yes
preaction discharges
Single-interlocked Water fills piping N/A w/detection, water Yes
preaction discharges
w/o detection, no
water in piping
Double-interlocked Water does not fill And Sprinkler piping fills Yes
preaction piping; preaction with water only if
control unit monitors detection and
sprinkler supervisory sprinkler is activated
pressure
Note 1. Action needed for sprinkler piping to fill with water.
Note 2. The sprinkler system piping is pressurized with air or nitrogen or maintains a vacuum to supervise the integrity of the sprinkler piping
network. If the system piping or a sprinkler is damaged, the supervisory pressure is reduced and a low air supervisory alarm is
activated. Supervision is also one portion of the releasing operation for double interlocked preaction systems.

2.4.7.1.3 Data Processing Equipment Rooms

The protection recommendations included in this section are based upon Li-ion batteries not being present
in the data processing equipment room as distributed battery back-up units in server racks or a UPS. When
battery back-up units and UPS Systems with Li-ion batteries are present provide protection in accordance with
Section 2.4.4.
A. To protect data processing equipment rooms with cable trays under a raised floor (See Figure 2.5.1.1.2),
provide FM Approved quick-response (QR) sprinklers with the following specifications:
1. Minimum density of 0.1 gpm/ft2 (4 mm/min)
2. Demand area of 1500 ft2 (140 m2) maximum spacing of 12 ft (3.6 m)
3. Sprinkler deflector distance from ceiling:
a. Minimum: 1.75 in. (44 mm)
b. Maximum: 4 in. (100 mm)
4. Maximum 30 ft (9 m) ceiling. (Refer to Section 3.2.5.1.)
5. Provide linear and area spacing of sprinklers in accordance with the recommendations in Data Sheet
2-0, Installation Guidelines for Automatic Sprinklers, for the designated hazard category up to a 30
ft (9 m) ceiling.
6. Hose allowance of 250 gpm (950 L/min)
7. Water supply duration of 60 minutes
B. To protect data processing equipment rooms with elevated cable trays having the following cable
arrangements, provide one of the fire protection options described below when the following conditions
are present:
1. Propagating (non-plenum-rated) communication/data cables in vertical bundles less than 3 in.
(76 mm) in diameter separated by 4 ft (1.2 m) distance
2. Propagating power or data cables, open raceways, or open trays in a single tier
3. Data processing equipment server racks constructed of noncombustible material
4. Raceways constructed of either noncombustible material or non-propagating plastic (See Section
2.2.8)
For cable arrangements listed in Item B above, provide one of the following protection options:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 17

a. A minimum 3 ft (0.9 m) clearance from the sprinkler to the cable tray. For a sprinkler with a cable
tray clearance of less than 3 ft (0.9 m), refer to the recommendations for reduced spacing in
accordance with Obstruction to Umbrella Discharge Pattern of Pendent and Upright Nonstorage
Sprinklers in Data Sheet 2-0.
b. A minimum pressure of 12 psi (0.8 bar) at the sprinkler or a maximum horizontal offset distance of
4 ft (1.2 m.) from the sprinkler to the cable trays above the servers.
C. When the following hazards are present, provide sprinkler design demands, hose demands, and
duration in accordance with the recommendations in Data Sheet 3-26 for Hazard Category 2 (HC-2) up
to a 30 ft (9 m) ceiling (refer to Section 3.2.5.1):
1. Propagating (non-plenum-rated) communication/data cables in vertical bundles greater than 3 in.
(76 mm) in diameter separated less than 4 ft (1.2 m)
2. Propagating power cables or data cables, open raceways or open cable trays if more than two tiers
high
3. Data processing equipment constructed of combustible material
4. Raceways constructed of combustible plastic
D. Provide protection for hot/cold aisle containment systems in accordance with Section 2.5.2.
2.4.7.1.4 Below Raised Floors and/or Above-Ceiling Spaces
A. Design the automatic extended coverage (EC) nonstorage sprinkler protection to deliver one of the
following densities:
1. 0.1 gpm/ft2 (4 mm/min) over 1500 ft2 (140 m2) within the raised floor space and/or above-ceiling
spaces for single tier open cable trays or on-floor cables to a maximum diameter of 6 in. (15 cm)
or less in width or diameter.
2. 0.2 gpm/ft2 (8 mm/min) over 2500 ft2 (232 m2) within the raised floor space and/or above-ceiling
spaces for multi-tier open cable trays, on-floor cables greater than a diameter of 6 in. (15 cm) or
where numerous large diameter bundles (greater than 6 in. [15 cm]) intersecting on the floor that can
spread fire in multiple directions.
B. When designed as a wet pipe system, use automatic EC nonstorage sprinklers with a temperature
rating of 165°F (74°C).
C. When designed as a dry pipe system, use automatic EC nonstorage sprinklers with a temperature
rating of 280°F (140°C).
D. Reduce the linear spacing of extended coverage (EC) nonstorage sprinklers in accordance with
Obstructions to Discharge Pattern of Pendent and Upright Nonstorage Sprinklers in Data Sheet 2-0,
Installation Guidelines for Automatic Sprinklers, to account for the specific deflector to floor distance and
provide an unobstructed discharge pattern for protection of cables in an open cable tray.
2.4.7.1.5 Preaction systems. When using a preaction type automatic sprinkler system for a non-interlock,
single-interlock, or double-interlock system throughout the data center, provide it in accordance with the
following recommendations:
A. Install in accordance with the applicable recommendations for a preaction sprinkler system in Data
Sheet 2-0, Installation Guidelines for Automatic Sprinklers and in addition to the following:
1. When using a non-interlock or single-interlock preaction sprinkler system arrangement, base the
sprinkler demand on a wet system.
2. In a double-interlock configuration, design the sprinkler system based on a dry system.
3. Provide a maximum water delivery delay of 30 seconds to the most remote sprinkler.
4. Provide a sectional valve above the preaction valve in accordance with Item D to allow proper
inspection, testing, and maintenance to be conducted in accordance with Data Sheet 2-81, Fire
Protection System Inspection, Testing and Maintenance.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 18 FM Global Property Loss Prevention Data Sheets

B. Activate the preaction valve with smoke detectors and control panel in accordance with Data Sheet
5-48, Automatic Fire Detection, in addition to the following:
1. Do not use heat detectors or standard-response smoke detectors for actuation of the preaction
sprinkler system.
2. Provide one of the following VEWFD detection methods in accordance with Section 2.4.6:
a. Air-aspirating smoke detection
b. Intelligent high-sensitivity spot detection
3. If both a preaction sprinkler system and clean agent fire extinguishing system are installed, provide
two independent VEWFD smoke detection systems. Provide the fire alarm threshold for the halocarbon
or inert gas (clean agent) fire extinguishing system lower than that for the preaction automatic sprinkler
system.
4. In a double-interlock preaction system, do not cross-zone detection for activation of the pre-action
system valve. Use the initiating signal of only one detector or detection system zone in the protected
area with detection at the air return.
In data halls with containment panels reaching up to the ceiling level a cross-zoned detection adds
another interlock level due to isolation of the smoke. This configuration will lead to a “triple” interlock
situation if applied to FM Approved double interlock preaction systems.
5. Annunciate an alert, pre-alarm and alarm condition in a constantly attended location when the
VEWFD detection has activated.
6. Provide a local visual and/or audible alarm within the protected area when an alarm condition is
activated.
7. Provide an alarm signal to the building fire alarm control panel area when an alarm condition is
activated.
8. Arrange the control valve for all preaction types of sprinkler systems to actuate upon:
a. the pre-alarm level or earlier for air-aspirating detection.
b. the pre-alarm for intelligent high-sensitivity spot detection.
C. Install an alarm valve for the sprinkler systems protecting the data center equipment room separate
from other sprinkler systems.
D. For a sprinkler system with a preaction valve, provide a 2 in. (50 mm) diameter test discharge line
located above (downstream from) the preaction sprinkler valve assembly (see Figure 2.4.7.1.5.D) for trip
testing of the preaction valve.
1. Install a normally closed indicating valve with supervision on the test discharge line.
2. Install a normally open indicating valve with supervision on the system riser above (downstream
from) the intake for the test discharge line.
E. Install the fire alarm control panel for the preaction sprinkler in accordance with the applicable
recommendations in Data Sheet 5-40, Fire Alarm Systems.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 19

To sprinklers

Normally open
Test indicating valve
discharge with supervision,
line for testing purposes

Normally closed Check

indicating valve valve To air or
with supervision, nitrogen
for testing purposes supply

Pre-action
valve

Indicating water
supply valve Water
supply

Fig. 2.4.7.1.5.D. Schematic of preaction valve with test discharge line

2.4.7.2 Water Mist Systems

2.4.7.2.1 An automatic water mist system FM Approved for “Protection of Data Processing Equipment
Rooms/Halls” may be used to protect a data processing equipment room with a forced air distribution system
having a maximum nominal upward velocity of 3.3 ft/s (1 m/s) through perforated floor openings, and
maximum 4 ft/s (1.2 m/s) horizontal airflow (or the provisions of forced air flow of its FM Approval listing).
2.4.7.2.2 Install water mist systems in accordance with all applicable recommendations in Data Sheet 4-2,
Water Mist Systems, and the manufacturer’s design, installation, operation, and maintenance manual shown
in the FM Approval listing for the specific application and the recommendations in this section of Data Sheet
5-32.
2.4.7.2.3 Provide one of the following types of automatic water mist systems (listed in order of preference
based on reliability and maintenance; refer to Section 3.2.5.2):
A. Wet system
B. Non-interlocked preaction system
C. Single-interlocked preaction system
D. Double-interlocked preaction system
The type of automatic water mist system (reference Table 2.4.7.1.1 for sprinklers) provided should consider
the impact of a delay in water being applied to the fire and ability to conduct maintenance. In particular, the
extended delay from a double-interlock preaction system requires both smoke detection and water mist
nozzle activation which can negatively impact control of the fire and the available water supply. In addition,
the complexity of the preaction valve trim decreases the availability of the fire protection system.
2.4.7.2.4 Provide a water supply for a 60-minute duration.
2.4.7.2.5 Preaction systems. When using a preaction type automatic water mist system as either a non-
interlock, single-interlock or double interlock system throughout the data processing equipment room, provide
it in accordance with the following recommendations:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 20 FM Global Property Loss Prevention Data Sheets

A. Install the system in accordance with the applicable recommendations for a preaction water mist system
in Data Sheet 4-2, Water Mist Systems.
1. Provide the nozzle water demand area in accordance with the FM Approval listing and the
manufacturer’s FM Approved Design, Installation, Operation and Maintenance manual.
2. Provide a maximum water deliver delay of 30 seconds to the most remote automatic nozzle.
3. Provide a sectional valve above the preaction valve in accordance with Item D to allow proper
inspection, testing, and maintenance to be conducted in accordance with Data Sheet 2-81, Fire
Protection System Inspection, Testing and Maintenance.
B. Activate the preaction valve with VEWFD smoke detectors and control panel in accordance with Data
Sheet 5-48, Automatic Fire Detection, in addition to the following:
1. Do not use heat detectors or standard-response smoke detectors for actuation of the preaction
sprinkler system.
2. Provide two independent VEWFD smoke detection systems if both a preaction automatic water mist
system and halocarbon or inert gas (clean agent) fire extinguishing system are installed, with the fire
alarm threshold for the clean agent system lower than that for the preaction automatic water mist
system.
3. In a double-interlock preaction system, do not cross-zone detection for activation of the pre-action
system valve. Use the initiating signal of only one detector or detection system zone in the protected
area with detection at the air return.
In data halls with containment panels reaching up to the ceiling level a cross-zoned detection adds
another interlock level due to isolation of the smoke. This configuration will lead to a “triple” interlock
situation if applied to FM Approved double interlock preaction systems.
4. Provide one of the following VEWFD detection methods in accordance with Section 2.4.6:
a. Air-aspirating smoke detection
b. Intelligent high-sensitivity spot detection.
5. Annunciate an alert, pre-alarm and alarm condition in a constantly attended location when the
pre-alarm and/or alert setting for the VEWFD detection has activated.
6. Provide a local visual and/or audible alarm within the protected area when an alarm condition is
activated.
7. Provide an alarm signal to the building fire alarm control panel area when an alarm condition is
activated.
8. Arrange the control valve for all preaction types of automatic water mist systems to actuate upon:
a. the pre-alarm level or earlier for air-aspirating detection.
b. the pre-alarm for intelligent high-sensitivity spot detection.
C. Install an alarm check valve for the water mist systems protecting the data processing equipment room
separate from other water mist systems.
D. For a water mist system with a preaction valve, provide a test discharge line located above (downstream
from) the preaction alarm check valve assembly (see Figure 2.4.7.1.4.D) for trip testing of the preaction
valve.
1. Install a normally closed indicating valve with supervision on the test discharge line.
2. Install a normally open indicating valve with supervision on the system riser above (downstream
from) the intake for the test discharge line.
E. Install the fire alarm control panel for the preaction water mist system in accordance with the applicable
recommendations in Data Sheet 5-40, Fire Alarm Systems.
2.4.7.2.6 Do not use water mist systems for the protection of overhead multi-tiered open cable trays of
propagating cables in the data processing equipment room.
2.4.7.2.7 For high-pressure water mist systems, use the supply pump specified in the FM Approval listing.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 21

2.4.7.2.8 Locate nozzles with respect to continuous and discontinuous obstructions in accordance with the
FM Approval listing.
2.4.7.2.9 When a low-pressure water mist system is supplied by the building sprinkler system, install a
separate water flow switch for the water mist system.
2.4.7.2.10 When protection of the area below the raised floor is provided by a water mist system, provide
an FM Approved automatic water mist system specifically listed for “Protection of Data Processing Equipment
Rooms/Halls - Below-Floor Protection” (see Section 2.4.4).
2.4.7.2.11 Use water mist systems protecting the area below a raised floor for the maximum number of tiered
open cable trays of propagating cables designated in the FM Approval listing.

2.4.7.3 Halocarbon and Inert Gas (Clean Agent) Fire Extinguishing Systems: Design Specifications
2.4.7.3.1 Construct the physical building envelop in accordance with Section 2.2 to maintain the design
concentration of clean extinguishing agent for whichever is the longer duration: 10 minutes, or until the
affected equipment or components can be de-energized.
2.4.7.3.2 Provide an FM Approved halocarbon or inert gas (clean agent) fire extinguishing system with
automatic actuation from FM Approved VEWFD detection, manual operation station, and emergency
mechanical manual operation at the clean agent storage cylinders.
2.4.7.3.3 Provide the FM Approved halocarbon or inert gas (clean agent) fire extinguishing system in
accordance with design and installation recommendations in Data Sheet 4-9, Halocarbon and Inert Gas
(Clean Agent) Fire Extinguishing Systems, and the manufacturer’s design, installation, and operation, manual
included in the FM Approval listing.
2.4.7.3.4 When a halocarbon clean agent fire extinguishing system is used, provide clean agent fire protection
systems in both the data processing equipment room and below the raised floor (see Section 3.2.5.3).
2.4.7.3.5 For the protection of data processing equipment (e.g., servers, electrical equipment, batteries, and
cables; refer to Section 2.8.4), do the following:
A. When the electrical equipment and/or cables are de-energized, provide the design concentration for
an ordinary combustible (Class A) fire in accordance with the system’s FM Approval listing.
B. When the electrical equipment and/or cables are not immediately de-energized but have a time delay
power disconnect, provide the design concentration for an energized electrical fire (Class C) identified
for the specific extinguishing agent in Appendix D.
2.4.7.3.6 Provide the proper clearance of the discharge nozzle(s) from the sidewall(s) of a hot/cold aisle
containment system or other obstructions (e.g., cable trays) in accordance with the manufacturer’s design,
installation, and operation manual included in the FM Approval listing (see Section 2.5.2).
2.4.7.3.7 When magnetic hard disk drives (HDD) and storage systems are susceptible to disruption of
performance by an excessive sound pressure level from the discharge of a clean agent fire extinguishing
system, do the following:
A. When possible, for FM Approved inert gas fire extinguishing systems use a regulated pressure system
to control flow and pressure from the discharge valve.
B. Use an FM Approved halocarbon or inert gas (clean agent) fire extinguishing system that has a noise
reducing discharge nozzle listed as a component of the fire extinguishing system. Install the discharge
nozzles as follows:
1. Determine the minimum radial distance based upon using the noise level or sound pressure level
that can produce damage to the hard disk drive in conjunction with the sound pressure level of the
discharge nozzle in the FM Approval listing.
2. Provide the discharge nozzle at a minimum radial distance from the hard disk drive for the discharge
nozzle area of coverage and ceiling height. Provide this in accordance with the FM Approved
manufacturer’s design, installation, operation and maintenance (DIOM) manual or acoustic calculation
method.
3. When the noise level or sound pressure level threshold for damaging the HDD is not available, use
100 dB in the calculation of the minimum radial nozzle distance.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 22 FM Global Property Loss Prevention Data Sheets

4. For inert gas fire extinguishing systems, when possible use discharge times from 60 seconds to
120 seconds.
C. When a FM Approved noise reducing discharge nozzle is not available as a component of the clean
agent fire extinguishing system, install the clean agent fire extinguishing system as follows to decrease
sound pressure levels:
1. Decrease the rate of flow of fire extinguishing system from the discharge nozzles used by increasing
the number of nozzles for a reduced area of coverage per nozzle.
2. When possible, provide discharge nozzles at a minimum of distance of 6.5 ft. (2 m) for small orifice
(3 - 8 mm) discharge nozzle(s) and 9.8 ft (3 m) for large orifice (15 – 20 mm) away from the server
racks.
3. For inert gas systems, use discharge times from 90 seconds to 120 seconds.
4. Provide the minimum nozzle pressure allowed by the FM Approval listing.
5. Ensure the noise pressure level of the peak nozzle pressure is below the allowable threshold of
the HDD equipment. When the allowable noise level or sound pressure level threshold for the HDD
is not available use 100 dB in the assessment.
D. Do not use pneumatic sirens as an alarm notification device.
E. Provide a Business Continuity Plan for any hard disk drives that are susceptible to disruption of
performance by noise from the discharge of a halocarbon or inert gas (clean agent) fire extinguishing
system in accordance with Section 2.7.4
2.4.7.3.8 When used in conjunction with a preaction sprinkler system, actuate the halocarbon or inert gas
(clean agent) fire extinguishing system using FM Approved intelligent high-sensitivity spot smoke detection
system in a matrix or counting configuration.
2.4.7.3.9 Design and install FM Approved VEWFD detection for the actuation of the halocarbon or inert gas
(clean agent) fire extinguishing system(s) in accordance with Data Sheet 5-48, Automatic Fire Detection,
and the manufacturer’s design, installation, and operation manual included with the FM Approval listing.
2.4.7.3.10 Do not use standard response smoke detectors for the actuation of halocarbon or inert gas (clean
agent) fire extinguishing systems.
2.4.7.3.11 When a halocarbon or inert gas (clean agent) fire extinguishing system is actuated by air-aspirating
VEWFD, do the following:
A. Annunciate all alert, pre-alarm, and alarm conditions to a constantly attended location.
B. Provide a local visual and/or audible alarm within the protected area.
C. Provide an alarm signal to the building fire alarm control panel area when any level (e.g., pre-alarm,
actuation) of smoke detection signal is received from the smoke detection system.
D. Arrange for the following to occur at the alarm condition for discharge of the halocarbon or inert gas
(clean agent) fire extinguishing system:
1. Shut down HVAC systems that:
a. supply outside make-up air (external from protected room).
b. are protecting combustibles only below the raised floor or only above ceiling space.
c. provide forced air distribution between multiple zones.
2. Automatically close fire and smoke dampers, as appropriate.
3. Power down data processing equipment as appropriate (see Section 2.8.2).
4. Discharge the clean agent after a non-recycling time delay not exceeding 30 seconds.
2.4.7.3.12 When a halocarbon or inert gas (clean agent) fire extinguishing system is actuated by intelligent
high-sensitivity spot smoke detection, do the following:
A. Annunciate all alert, pre-alarm or alarm conditions to a constantly attended location.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 23

B. From activation of the first spot smoke detector, provide local visual and/or audible alarm within the
protected area.
C. From activation of the second spot smoke detector for discharge of the halocarbon or inert gas (clean
agent) fire extinguishing system arrange for the following to occur:
1. Shut down HVAC systems that:
a. supply outside make-up air (external from protected room).
b. have a clean agent fire extinguishing system protecting combustibles only below the raised floor
or only above ceiling space.
c. provide ventilation between multiple zones.
2. Close fire and smoke dampers from activation of the second detector.
3. Power down data processing equipment as appropriate (see Section 2.8.2).
4. Discharge the clean agent after a non-recycling time delay not exceeding 30 seconds.
2.4.7.3.13 For HVAC systems that do not introduce makeup (outside) air, the forced air distribution system
does not need to be shut down when both of the following are provided:
A. A cooling air system that only recirculates air within the data processing equipment space (e.g., CRAH
and CRAC) unless the data processing equipment is interlocked to shut down on agent discharge.
B. Sufficient clean agent is provided for the volume of HVAC system ducts and components open to the
protected space as part of the total hazard volume.
2.4.7.3.14 Provide permanently connected clean agent supply cylinder(s) as a reserve for the halocarbon
or inert gas (clean agent) fire extinguishing system when:
A. providing sole protection of the data center or data processing equipment room (see Section 2.4.3).
B. providing simultaneous supplementary equipment protection of multiple data processing equipment
rooms.
2.4.7.3.15 Provide an FM Approved fire extinguishing system releasing device that is electrically compatible
with the clean agent fire extinguishing system actuation device and interfaces with the smoke detection and
fire alarm systems.
2.4.7.3.16 Locate abort switches, when provided, within the interior of the room and near a means of egress.
A. Provide a type that requires positive manual pressure to prevent discharge of the halocarbon or inert
gas (clean agent) fire extinguishing system.
B. Provide manual alarm stations and emergency manual activation devices to override the abort mode
to allow immediate discharge of the clean agent fire extinguishing system.
C. Provide both distinctive audible and visual indication of the halocarbon or inert gas (clean agent) fire
extinguishing system in abort mode.
D. Provide a placard that identifies the abort switch and purpose.
2.4.7.3.17 Conduct a door fan test in accordance with Data Sheet 4-9, Halocarbon or Inert Gas (Clean Agent)
Fire Extinguishing Systems, subsequent to the halocarbon or inert gas (clean agent) fire extinguishing system
installation to verify the clean agent concentration will be maintained at the design concentration for the
recommended retention time and analyze there is sufficient venting and/or leakage area in order not to
over-pressurize the enclosure. Modify the protected space envelope and repeat the test until acceptable
results are attained.
2.4.7.3.18 Provide a plan and means to ventilate the protected area from the discharge of the clean agent
and byproducts of decomposition without contamination to other equipment and areas.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 24 FM Global Property Loss Prevention Data Sheets

2.5 Equipment and Processes

2.5.1 Servers, Mainframes, and Supercomputers

2.5.1.1 Equipment
2.5.1.1.1 Use equipment and replacement parts that are listed to safety standards for their intended purpose
by a nationally recognized testing laboratory (NRTL).
2.5.1.1.2 Provide server enclosures (e.g., cabinets) and racks constructed of noncombustible materials. See
Figure 2.5.1.1.2 for a typical server cabinet and rack arrangement.

Fig. 2.5.1.1.2. Typical server cabinet and rack arrangement

2.5.1.1.3 Provide blanking plates for empty server slots constructed of one of the following (listed in order
of preference) when used in server racks to route air flow in the equipment racks or hot/cold aisle containment
system:
A. Metal
B. Noncombustible material
C. Plastic that has been specification-tested to FM Approval Standard Class 4910 (listed under “Building
Material” in the Specification Tested section of the Approval Guide).
D. FM Approved plastic interior wall finish materials that have been specification tested to FM Approval
Standard Class 4882 for use in smoke-sensitive occupancies.
2.5.1.1.4 If data processing equipment is liquid-cooled, provide an alarm to indicate fluid leakage in
accordance with Data Sheet 1-24, Protection Against Liquid Damage.
2.5.1.1.5 If a liquid is used for lubrication and/or cooling of the equipment, use one of the following:
A. A container of sealed construction
B. A nonignitable liquid
C. Vent/pressure relief on a container that is pressurized to a safe location.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 25

2.5.1.1.6 Provide proper grounding for equipment in accordance with Data Sheet 5-19, Switchgear and Circuit
Breakers, Data Sheet 5-20 Electrical Testing, and the manufacturer’s instructions.

2.5.1.2 Protection
2.5.1.2.1 When it is essential to reduce equipment damage from an incipient fire to minimum possible levels,
or to facilitate a return to service, provide an FM Approved halocarbon or inert gas (clean agent) fire
extinguishing system with VEWFD detection to protect the data equipment within the data processing
equipment room. This is to supplement the automatic sprinkler or water mist system protection protecting the
data processing equipment room.
2.5.1.2.2 Install the halocarbon or inert gas (clean agent) fire extinguishing system in accordance with the
applicable recommendations in Section 2.4.7.3.
2.5.1.2.3 Install FM Approved very early warning fire detection (VEWFD) to actuate the halocarbon or inert
gas (clean agent) fire extinguishing system in accordance with Section 2.4.7.3.

2.5.2 Hot/Cold Aisle Containment and Hot Collar Systems

2.5.2.1 Provide containment systems constructed of one of the following (listed in order of preference):
A. Noncombustible materials
B. FM Approved plastic containment panels listed to Class 4884, Panels Used in Data Processing Center
Hot and Cold Aisle Containment Systems.
C. FM Approved plastic interior wall finish materials that have been tested to FM Approval Standard Class
4882 for use in smoke-sensitive occupancies.
2.5.2.2 If a solid containment ceiling is installed as a portion of the hot/cold aisle containment system, provide
one of the following:
A. Adequate automatic fire protection (e.g., sprinklers, water mist, or clean agent) beneath the ceiling
(designed per Section 2.4.7 and 2.5.2.4)
B. FM Approved (Class 4651) drop-out ceiling panels in conjunction with adequate automatic fire protection
at ceiling level in the data processing equipment room. Install drop-out ceiling panels in accordance with
Data Sheet 1-12, Ceilings and Concealed Spaces, and the following:
1. Use quick-response sprinklers or quick-response automatic water mist nozzles installed at ceiling
level.
2. Limit the height of the drop-out ceiling panels above the floor to 15 ft (4.5 m).
3. Limit the distance between the drop-out ceiling panels and the sprinklers located above the ceiling
to 20 ft (6.0 m).
4. Limit the distance between the drop-out ceiling panels and the automatic water mist nozzle located
at ceiling level to the maximum ceiling height in the water mist system’s FM Approval listing.
2.5.2.3 If containment curtains or other vertical partitions form part of the containment system or hot collar
such that the automatic fire protection at ceiling level can be obstructed, do one of the following:
A. Locate the partitions so they do not impede the discharge of the protection system for the contained
area.
B. Provide additional discharge devices (e.g., automatic sprinklers, water mist nozzles, or clean agent
nozzles) for the automatic fire protection (designed per Section 2.4.7 and 2.5.2.4) in the contained area.
2.5.2.4 When protection is provided within the containment system, provide the following:
A. FM Approved quick-response (QR) sprinklers with a minimum density of 0.1 gpm/ft2 (4 mm/min) over
1500 ft2 (140 m2), or
B. FM Approved quick-response automatic water mist nozzles arranged in accordance with their FM
Approval listing.
C. Sprinkler deflector or nozzle distance from the ceiling:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 26 FM Global Property Loss Prevention Data Sheets

• Minimum: 1.75 in. (44 mm)

• Maximum: 4 in. (100 mm)
D. A hose allowance of 250 gpm (950 L/min).
2.5.2.4.1 If a grated ceiling is installed as part of the hot aisle containment system, provide a maximum spacing
of 4 ft (1.2 m) between sprinklers or automatic water mist nozzle at the ventilation ceiling and plenum
interface.
2.5.2.5 Do not use the following containment devices as alternatives to providing sprinklers below the ceiling
or within the containment system:
A. Using containment panels mounted with fusible links.
B. Automatic releases on curtains and panels.
2.5.2.6 When hot collar systems are used (see Figure 2.5.2.11.C), evaluate sprinkler locations for obstructions
in accordance with Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers.
2.5.2.7 If the data processing equipment room and exhaust/air return (see Section 2.4.5) has been provided
with an FM Approved VEWFD system, no detection is needed beneath a solid cold aisle containment ceiling.
2.5.2.8 Arrange and install detection in the hot aisle containment system or hot collar in accordance with
the manufacturer’s design guide and/or application guide for this specific application.
2.5.2.9 When containment systems are added to existing sever racks and the data processing equipment
room has been equipped with FM Approved standard response spot-type smoke detection, provide smoke
detection beneath the containment ceiling.
2.5.2.10 Verify the FM Approved detection within the containment system (hot aisle) is listed for the ambient
temperature of its location.
2.5.2.11 If a halocarbon or inert gas (clean agent) fire extinguishing system is installed for the containment
system, provide the following:
A. The proper clearance of the discharge nozzle(s) from the sidewall(s) of the containment system is
provided in accordance with the clean agent fire extinguishing system manufacturer’s design, installation,
and operation manual included with the FM Approval listing.
B. The proper clean agent design concentration within the volume of the containment system.
C. The proper clean agent design concentration surrounding the containment system(s).
D. A halocarbon or inert gas (clean agent) fire extinguishing system designed in accordance with Section
2.4.7.3.
Figures 2.5.2.11.A and 2.5.2.11.B provide conceptual views of cold aisle and hot aisle containment systems
with vertical air flow. Figure 2.5.2.11.C provides a conceptual view of a hot collar containment system with
vertical air flow. Figures 2.5.2.11.D provides a conceptual view of a hot and cold aisle containment systems
for horizontal air flow with no raised floor.
Note: There are other containment configurations used to control the cooling of servers.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 27

Loose seal barrier

for pressure balance

Server Server
cabinets cabinets
Hot aisle (side view)
Cold (side view) Hot aisle
aisle
CRAC

Fig. 2.5.2.11.A. Conceptual view of cold aisle containment system

Loose seal barrier

for pressure balance

Server Server
cabinets cabinets
Cold aisle (side view) (side view) Cold aisle
CRAC Hot aisle

Fig. 2.5.2.11.B. Conceptual view of hot aisle containment system

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 28 FM Global Property Loss Prevention Data Sheets

Server Server
cabinets cabinets
(side view) (side view)
CRAC

Fig. 2.5.2.11.C. Conceptual view of hot collar containment system

Fig. 2.5.2.11.D. Conceptual view of hot/cold aisle with horizontal air flow without a raised floor

2.5.3 Tape Cartridge Storage

2.5.3.1 Automated Tape Cartridge Storage Units

A fire inside any automated tape cartridge storage unit can cause significant nonthermal damage to electronic
equipment in the surrounding space.
2.5.3.1.1 Use tape cartridge cassettes constructed of one of the following:
A. Noncombustible materials

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 29

B. Plastics that have been specification-tested to FM Approval Standard 4910. Specification-tested

products are listed in the Building Material section of the Approval Guide.
2.5.3.1.2 When tape cartridges are constructed of combustible materials, provide all of the following:
A. An FM Approved very early warning fire detection (VEWFD) system in the cabinet in accordance with
Section 2.4.6.
B. An interlock with smoke detection to de-energize the electrical service to the cabinet in accordance
with Section 2.8.2.
C. Protection from one of the following within each unit:
1. Automatic sprinkler protection per Section 2.4.7.1 in accordance with protection being provided by
the ceiling sprinkler system.
2. A halocarbon and inert gas (clean agent) fire extinguishing system with extended discharge in
accordance with Section 2.4.7.3.
3. A carbon dioxide fire extinguishing system, if the automated tape cartridge storage unit is an
unoccupiable enclosure or space.
a. Design and install the carbon dioxide system in accordance with Data Sheet 4-11N, Carbon Dioxide
Fire Extinguishing Systems.
b. Use a minimum 50% design concentration for the hazard.

2.5.3.2 Tape Cartridge Storage Rooms

2.5.3.2.1 Provide a separate room for tape cassette storage with minimum 1-hour fire-rated walls that span
from slab to slab. Ensure any doors and windows to this room have a minimum 1-hour fire-rating.
2.5.3.2.2 Provide automatic sprinkler protection in accordance with the recommendations for solid piled
storage of unexpanded plastics in Data Sheet 8-9, Storage of Class 1, 2, 3, 4 and Plastic Commodities.
2.5.3.2.3 When it is essential to limit damage to an incipient fire, provide an FM Approved clean agent fire
extinguishing system with detection to protect the tape storage room. This is to supplement the automatic
sprinkler in protecting the facility. Install the halocarbon or inert gas (clean agent) fire extinguishing system
in accordance with Section 2.4.7.3.
2.5.3.2.4 To further minimize the potential for a serious incident, do the following:
A. Control access to the cassette storage room (e.g., lock doors).
B. Back-up cassettes to an offsite location.
2.5.3.2.5 Provide fire hose connections for rooms containing movable aisle storage. Locate connections for
fire hoses to reach all sections of the movable storage units.

2.5.4 Mobile/Modular Data Centers

2.5.4.1 Construction
2.5.4.1.1 Build the structure, exterior enclosure, and interior surfaces using noncombustible materials. If the
mobile/modular data center is insulated, provide noncombustible or FM Approved Class 1-rated insulation.
2.5.4.1.2 Structurally connect containers when configured in a vertical array.

2.5.4.2 Exposures
2.5.4.2.1 Interior Installations
When the mobile/modular data center is installed in a building, provide automatic sprinkler protection for
the hazards associated with the enclosing building construction, the exterior of the mobile/modular data
center, and other contents in the enclosing building in accordance with the applicable occupancy-specific data
sheet.
2.5.4.2.2 Exterior Installations

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 30 FM Global Property Loss Prevention Data Sheets

When a mobile/modular data center is exposed to weather conditions, design, construct, install, and operate
modules to meet the recommendations in applicable natural hazards data sheets, including, but not limited
to, the following:
• Data Sheet 1-28, Wind Design
• Data Sheet 1-34, Hail
• Data Sheet 1-54, Roof Loads for New Construction
• Data Sheet 5-11, Lightning and Surge Protection for Electrical Systems
• Data Sheet 9-18, Prevention of Freeze-Ups
• Data Sheet 9-19, Wildland Fire
2.5.4.2.3 Natural Hazards
For both interior and exterior installations, design, construct, install, and operate modules to meet the
recommendations in applicable natural hazards data sheets, including, but not limited to, the following:
• Data Sheet 1-40, Flood
• Data Sheet 1-2, Earthquakes
In addition to adhering to the recommendations in Data Sheet 1-2, Earthquakes, provide the following:
A. Seismic restraint to the data processing equipment and utilities in the mobile/modular data center for
the forces identified in Data Sheet 1-2.
B. Seismic anchoring of the mobile/modular data center exterior enclosure to the surface (ground, floor,
or other mobile/modular data centers).

2.5.4.3 Fire Detection

Provide very early warning fire detection (VEWFD) systems in mobile/modular data centers per Section 2.4.6.

2.5.4.4 Fire Protection

2.5.4.4.1 Provide protection for mobile data centers using one of the following:
A. Halocarbon or inert gas (Clean agent) fire extinguishing system actuated by VEWFD detection, or
B. Automatic sprinklers inside the mobile/modular data center per Section 2.4.7.1, or
C. Automatic water mist systems inside the mobile/modular data center per Section 2.4.7.2.
2.5.4.4.2 When the fire protection system equipment (i.e., storage cylinders and actuation controls) is located
inside the mobile/modular data center, provide manual and emergency manual actuation devices for
operation outside the entrance to the mobile/modular data center.
2.5.4.4.3 Provide protection for any specific hazard(s) in an equipment module in accordance with the
applicable data sheet (e.g., emergency diesel generators).

2.5.4.5 Equipment Power Isolation

Provide automatic interlocks and power isolation to de-energize equipment in accordance with Section 2.8.2.

2.5.5 Network/Broadcast Control Rooms

This section provides recommendations for monitoring operations, network operations centers, broadcast,
and other similar control rooms. For these occupancies, the following recommendations take precedence over
other recommendations within this data sheet.

2.5.5.1 Materials
Use noncombustible materials to construct control rooms.

2.5.5.2 Cables
2.5.5.2.1 Use FM Approvals Group 1 or plenum-rated cable in accordance with Section 2.2.7.
2.5.5.2.2 Protect grouped cables and cable trays in accordance with Data Sheet 5-31, Cables and Bus Bars.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 31

2.5.5.2.3 Seal all cable and signal wire penetrations with FM Approved penetration seals with fire ratings
equal to those of the surrounding construction.

2.5.5.3 Protection
2.5.5.3.1 Provide sprinkler design demands, hose demands, and duration in accordance with the
recommendations for an HC-1 hazard category in Data Sheet 3-26, Fire Protection Demand for Nonstorage
Sprinklered Properties.
2.5.5.3.2 Provide automatic smoke detection in the following places:
A. In control rooms, including control panels that extend to or near the ceiling
B. Beneath raised floors and above suspended ceilings that contain a significant quantity of combustible
grouped cables
C. In large cabinets with either combustible construction or combustible cables
2.5.5.3.3 Install FM Approved smoke detection in accordance with Data Sheet 5-48, Automatic Fire Detection.

2.5.6 Diagnostic Equipment

The recommendations in this data sheet for diagnostic equipment are intended for protection of the
equipment.
2.5.6.1 Locate and protect the diagnostic equipment from flood and storm water runoff in accordance with
Section 2.2.12.
2.5.6.2 Do not locate roof drains, domestic water lines, or other liquid piping that is not essential for operations
in the diagnostic equipment room.
2.5.6.3 Provide automatic wet sprinkler protection throughout the building in which the diagnostic equipment
(e.g., magnetic resonance imaging [MRI], computerized axial tomography [CAT] scan, Cyclotron) is located
in accordance with the appropriate occupancy per Data Sheet 3-26, Fire Protection Demand for Nonstorage
Sprinklered Properties.
2.5.6.4 Provide FM Approved smoke detection in accordance with Data Sheet 5-48, Automatic Fire Detection.
2.5.6.5 Provide an automatic sprinkler system, wet or preaction, throughout diagnostic equipment areas.
2.5.6.5.1 Provide sprinkler design demands, hose demands, and duration for hazard category 1 (HC-1) up
to a 30 ft (9 m) ceiling in accordance with the recommendations in Data Sheet 3-26, Fire Protection Demand
for Nonstorage Sprinklered Properties.
2.5.6.5.2 Use FM Approved sprinklers constructed of nonferrous material.
2.5.6.5.3 Provide automatic quick-response (QR) sprinklers with a temperature rating of 165°F (74°C).
2.5.6.5.4 Provide sprinkler spacing in accordance with Data Sheet 2-0, Installation Guidelines for Automatic
Sprinklers.
2.5.6.5.5 Install nonferrous piping (e.g., copper, stainless steel, CPVC plastic) for the automatic sprinkler
system with dielectric fittings in the diagnostic equipment area.
2.5.6.5.6 When plastic pipe is used, install it as follows:
A. Use FM Approved CPVC pipe with a wet sprinkler system.
B. Verify the diagnostic equipment hazard is similar to a Hazard Category 1 (HC-1) occupancy as identified
in Data Sheet 3-26, Fire Protection Demand for Nonstorage Sprinklered Properties.
C. In accordance with the recommendations for CPVC pipe in Data Sheet 2-0, Installation Guidelines
for Automatic Sprinklers.
2.5.6.5.7 If installing a preaction sprinkler system, install it in accordance with Section 2.4.7.1.
2.5.6.6 Provide protection of a control room for diagnostic equipment in accordance with Section 2.5.5.
2.5.6.7 Provide portable fire extinguishers in accordance with Section 2.4.2 and this section.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 32 FM Global Property Loss Prevention Data Sheets

2.5.6.7.1 When magnetic diagnostic equipment is present, provide the following:

A. A portable fire extinguishers with non-magnetic construction.
B. Verification that the magnetic force rating of the portable fire extinguisher is compatible with the
maximum magnetic force of the diagnostic equipment such that it does not pose a magnetic hazard.
C. Verification that the portable fire extinguisher is located no less than the manufacturer’s minimum
specified distance from the magnetic diagnostic equipment.

2.5.7 Quantum Computers

See Section 3.3.6 for information on Quantum computers.

2.6 Inspection, Testing, and Maintenance

Establish and implement a data center utility and support system equipment inspection, testing, and
maintenance program, including electrical, HVAC and all support systems. See Data Sheet 9-0, Asset
Integrity, for guidance on developing an asset integrity program.

2.6.1 Facilities

2.6.1.1 Housekeeping
Provide regular housekeeping inspections with the following goals:
A. Potential ignition sources are controlled (e.g., smoking, hot work, temporary heaters, cooking
equipment).
B. The accumulation of combustible materials is prevented.
C. Ordinary combustibles are not stored inside or behind control cabinets.
D. Necessary routine spare parts, manuals, etc. are kept in normally closed metal cabinets.

2.6.1.2 Penetrations
A. Develop procedure(s) to manage the state of penetrations within the data center to control smoke
damage and maintain the construction fire-resistance rating. At a minimum, include the following:
1. Location of the current or new penetration to be opened
2. Issuance of a permit for the opening of the penetration
3. Confirmation the work is completed and penetration is sealed or resealed
4. Removal and retention of the permit as a record of the work
5. Periodic audits of penetration locations to determine the procedure is being followed
B. Verify the integrity of penetration sealing on a minimum yearly basis.
C. Seal new penetrations identified from inspection or penetrations when the integrity is compromised in
accordance with Section 2.2.4 Penetrations.

2.6.2 Heating, Ventilation and Air Conditioning (HVAC)

A. Inspect, test, and maintain HVAC systems and controls for data processing equipment spaces per
equipment manufacturer’s recommendations. See Data Sheet 1-45, Air-Conditioning and Ventilation
Systems and Data Sheet 7-13, Mechanical Refrigeration. Also see Data Sheet 13-24, Fans and Blowers,
for fan guidance. For cooling tower guidance, see Data Sheet 1-6, Cooling Towers.
B. When ventilation interlocks are provided to reduce air flow, test the interlock between the fire protection
and ventilation system on an annual basis.
C. Liquid Systems: Inspect, test, and maintain piping systems as part of the asset integrity program to
verify piping integrity. See Data Sheet 1-24, Protection Against Liquid Damage, for guidance on mitigating
damage associated with a liquid release.
D. Filters: Clean or replace HVAC filters on a regular schedule and as needed to maintain efficiency and
prevent dust and lint accumulations (See Data Sheet 1-45, Air Conditioning and Ventilation Systems).

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 33

E. Drains: Develop a procedure for recording inspection and cleaning of HVAC drains on a regular basis.

2.6.3 Fire Protection

2.6.3.1 Inspect and test the various fire protection system(s) in accordance with the applicable
recommendations in Data Sheet 2-81, Fire Protection System Inspection, Testing and Maintenance and Other
Fire Loss Prevention Inspections.
2.6.3.2 Where a preaction valve is used, provide a test discharge line (see Figure 2.4.7.1.4.D) to verify
operation of the preaction valve of the sprinkler system and to ensure the preaction system piping is arranged
to keep water from entering the piping system.
A. During the test, close the trip test cutoff indicating valve on the system riser and open the indicating
valve on the discharge test line.
B. Actuate the preaction system in conjunction with smoke detection system.
C. Immediately following the test, return the system to normal position.
D. Use FM Global’s Red Tag Permit System when the trip test cutoff indicating valve is closed, and follow
the precautions for fire protection being out of service described in Data Sheet 2-81.
E. When disabling the detection system for other testing of the preaction sprinkler system this is regarded
as an impairment of fire protection.
2.6.3.3 If a flushing investigation is recommended in accordance with Data Sheet 2-81, use a videoscope
inspection to verify there is no scale or debris in the piping that could clog a sprinkler. Only use this inspection
method if a satisfactory water delivery time was confirmed during the acceptance test.
2.6.3.4 Test the VEWFD system annually to verify proper operation in accordance with the applicable
recommendations in Data Sheet 5-48, Automatic Fire Detection, and Appendix C (typical test method).
2.6.3.5 Inspect the integrity of the enclosure protected by a halocarbon or inert gas (clean agent) fire
extinguishing system to determine if:
A. changes have occurred that could change volume, hazard, or both.
B. penetrations have occurred that could lead to extinguishing agent leakage.
2.6.3.5.1 If an administrative control program is used to document the enclosure integrity, inspect the
enclosure every 36 months. If an administrative control program is not used, inspect at least once every 12
months.
2.6.3.5.2 Use a blower door fan unit to verify extinguishing agent concentration will be maintained if
uncertainty exists about the integrity of the enclosure.
2.6.3.6 Maintain fire protection systems in accordance with the applicable recommendations in Data Sheet
2-81, Fire Protection System Inspection, Testing and Maintenance and Other Fire Loss Prevention
Inspections.
2.6.3.7 Manage impairments identified by periodic inspections, testing, and maintenance in accordance with
the recommendations in Data Sheet 2-81, Fire Protection System Inspection, Testing and Maintenance and
Other Fire Loss Prevention Inspections.

2.6.4 Electrical Power Distribution

2.6.4.1 Inspect, test, and maintain switchgear and battery systems in accordance with Data Sheet 5-19,
Switchgear and Circuit Breakers, and power distribution transformers in accordance with Data Sheet 5-4,
Transformers.
2.6.4.2 Inspect, test, and maintain electrical equipment, including automatic transfer switches in accordance
with Data Sheet 5-20, Electrical Testing and UPS systems in accordance with Data Sheet 5-28, DC Battery
Systems.
2.6.4.3 Inspect, test, and maintain emergency power systems in accordance with Data Sheet 5-23, Design
and Protection for Emergency and Standby Power Systems, Data Sheet 13-26, Internal Combustion Engines
and Data Sheet 5-28, DC Battery Systems.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 34 FM Global Property Loss Prevention Data Sheets

2.6.4.4 Verify a documented inspection, testing and maintenance plan is in place for any portion of the
electrical system operated by the utility on site.

2.7 Human Element

Develop, maintain, and train operators on standard and emergency operating procedures for utility and
support system equipment. See Data Sheet 10-8, Operators, for guidance on developing operator programs.

2.7.1 Emergency Response Team (ERT)

2.7.1.1 Use Data Sheet 10-1, Pre-Incident and Emergency Response Planning, as a resource to develop
a plan and procedures.
2.7.1.2 Provide emergency response personnel with, at minimum, procedures for and authorization to do
the following:
A. Interrupt electrical power at the ignition source as outlined in the power isolation plan (see Section
2.7.2).
B. Isolate leaking water used for cooling of data processing equipment at the closest control valve. Use
Data Sheet 1-24, Protection Against Liquid Damage, as a resource to develop a plan and procedures.
C. Notify the fire service.
D. Operate extinguishing equipment.
2.7.1.3 Develop a pre-incident plan with the local fire service. At a minimum the plan should include the
following:
A. A tour
B. A description of the facilities and equipment
C. Implementation of the power isolation plan
2.7.1.4 Use Data Sheet 9-1, Supervision of Property, as a resource to develop a plan and procedures to
prevent unauthorized access the premises and assets.

2.7.2 Power Isolation Plan

2.7.2.1 Develop a detailed power-isolation plan that includes formal procedures for de-energizing data and/or
HVAC equipment to reduce damage, contamination from smoke, and prevent reignition. The goal of the
procedures should be to selectively isolate equipment within an affected cabinet, row, or zone, and to enable
personnel to respond to an event requiring complete power isolation of a room or building in a timely but
expeditious sequence to prevent propagation and reignition. Power isolation at the room level should be
initiated when the fire protection system(s) activate.
2.7.2.2 At a minimum, include the following items in the power-isolation plan:
A. A description (for the ERT and fire service) of the data processing equipment and HVAC systems within
the building and how they are powered and isolated or de-energized. Include all sources of power,
including commercial power, batteries, and generators to the fire area.
B. The functions of disconnect controls (e.g., switch/button, circuit breaker, switch gear) for powering down
or de-energizing the data processing equipment and/or HVAC system in the data center (See Section
2.7.7).
C. The location of the manual control(s), remote manual control(s), and disconnect control(s) for powering
down the data processing equipment and/or HVAC system.
D. Label power sources to the equipment room (electrical panels, PDUs, etc.) to show the areas/equipment
they control so specific equipment can be quickly located and de-energized.
E. If multiple zones are used, identify the data processing equipment or HVAC system associated with
each zone.
F. When to use the manual remote override disconnect control for de-energizing data processing
equipment and/or HVAC system.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 35

G. The impact from the activation of individual data processing equipment power switches.
H. Identify the responders who are designated to do the following:
1. Isolate all sources of power, including commercial power, batteries and generators to the fire area.
2. Notify the fire service and management designated to authorize implementation of the power
isolation plan from a constantly attended location.
3. Meet fire service personnel.
4. Advise the fire service personnel of power sources, disconnect controls, and depowering methods.
I. Post the following information for the fire service inside the designated entrance:
1. Floor plans
2. Contact names and phone numbers of personnel responsible for the site.
3. Location of emergency power disconnect controls
J. Pre-plan the previous items with the fire service.
K. Drill procedures with the emergency response team (ERT).
2.7.2.3 When halocarbon or inert gas (clean agent) fire extinguishing systems are installed with automatic
power-down and time delay, ensure the following, at a minimum:
A. Manual power-down can be completed in a maximum of 10 minutes as part of the soft switch process,
at which time automatic depowering of the data processing equipment is initiated.
B. The halocarbon or inert gas (clean agent) fire extinguishing system is qualified to account for continuous
forced-air distribution during the time delay (see Section 2.4.6.3).
C. The design concentration for energized data processing equipment is maintained at a minimum until
the controlled or automatic “soft” shut down is complete.
2.7.2.3.1 Contact the data processing equipment manufacturer for assistance in the powering down of data
processing equipment and the appropriate initiating device to use for automatic power down.
2.7.2.4 Review the power isolation plan at least quarterly.
2.7.2.5 Test or drill the power isolation procedures and methods at least annually with all individuals involved
in the plan.
2.7.2.5.1 Conduct walk-through drills in which power isolation is simulated for different fire scenarios and
fire propagation levels.
2.7.2.6 Train designated responder(s) to properly operate circuit breakers and disconnect equipment.

2.7.3 Disaster Recovery Plan

2.7.3.1 Develop a detailed written disaster recovery plan for the data center based upon a complete loss
of facility and services.
2.7.3.2 Develop the disaster recovery plan based on the applicable recommendations in Data Sheet 10-5,
Disaster Recovery Planning.
2.7.3.3 Annually review and test the plan to ensure it is up to date and functional.

2.7.4 Business Continuity Plan

2.7.4.1 Develop a detailed written business continuity plan based on a complete loss of facilities or services.
Address the following in the plan:
• Executive management support
• Utilization/relocation of personnel
• Facilities, equipment (including equipment contingency planning, service interruption planning, and power
isolation planning)
• IT/telecom
• Suppliers
• Clients
• Plan implementation and testing

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 36 FM Global Property Loss Prevention Data Sheets

2.7.4.2 Review and test the plan annually to ensure it is up to date and viable.

2.7.5 Security
2.7.5.1 Design buildings for security in accordance with Data Sheet 9-1, Supervision of Property, and
recommendations in this section.
2.7.5.2 Establish a procedure and method, such as card access, to verify that an individual entering the facility
is authorized to do so.
2.7.5.3 Have entrances to buildings and floors secured, and use a secure access system to verify employees
and visitors.
2.7.5.4 Limit unescorted visitors to unsecured-open areas. Have visitors escorted to all other areas.
2.7.5.5 Admit only authorized personnel to the data processing equipment room and other critical areas (e.g.,
cartridge storage rooms, UPS rooms, battery rooms, network/fiber room, switchgear). Keep these areas
secured with locks or electronic key systems.
2.7.5.6 Protect routine spare electronic components, such as circuit boards, from theft (see Data Sheet 9-16,
Burglary and Theft).
2.7.5.7 Verify authorized personnel have access (e.g., master key, passcode) to equipment protected by
locks in order to gain access in the event of a fire.
2.7.5.8 Install an FM Approved Level 1 or better intrusion alarm system for data and record storage rooms
if these areas are provided with emergency doors exiting outside the secure area.
2.7.5.9 Install an FM Approved Level 2 or better intrusion alarm system if previous experience indicates this
need (see Data Sheet 9-16, Burglary and Theft).
2.7.5.10 Provide the alarm system with line supervision or a loud local alarm and provide a response level
that meets FM-15 per Data Sheet 9-16, Burglary and Theft.
2.7.5.11 See Data Sheet 9-16, Burglary and Theft, for additional details regarding the recommendations
above, and for additional recommendations related to the installation of an intrusion alarm system.
2.7.5.12 Provide a procedure and method for preventing contractors who are using servicing computers for
equipment maintenance from introducing a cyber risk (e.g., viruses, malware) to the information technology
network.
2.7.5.13 Provide a procedure and method for physical destruction of data storage devices (e.g., hard disk
drives) that are no longer in service.

2.7.6 Flood Emergency Response Plan

For locations in which the predicted 500-year flood will result in onsite flooding, develop a detailed written
flood emergency response plan (FERP) for the data center and related facilities using the applicable
recommendations in Data Sheet 10-1, Pre-Incident Planning.

2.7.7 Contingency Plan

2.7.7.1 Equipment Contingency Planning (ECP)

When a data center utility and/or support system equipment breakdown results in an unplanned outage to
site processes and systems considered key to the continuity of operations, develop and maintain a
documented, viable utilities and support system equipment contingency plan (ECP) per Data Sheet 9-0, Asset
Integrity. See Appendix C of that data sheet for guidance on the process of developing and maintaining a
viable equipment contingency plan. Also refer to sparing, rental, and redundant equipment mitigation strategy
guidance in that data sheet.
To develop the data center ECP, conduct a systematic, strategic assessment of data center utilities and
support system equipment. Consider process bottlenecks, single points of failure, unique and long lead time
equipment, evaluate equipment integrity, reliability and remaining useful life, fitness for service, and operating
history/trends. Evaluate the type and scope of ECP needed to mitigate the equipment specific breakdown
exposures.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 37

The data center ECP includes recovery options and mitigation strategies to respond to and recover from
the equipment breakdown exposures, focusing on electrical and cooling equipment. This can include repair,
replacement, rental lead time options, used and/or surplus equipment, redundancy, and sparing to minimize
the downtime.
Consider the impact of the failure of an automatic transfer switch (ATS) or emergency/standby power systems
and switchgear when evaluating equipment contingency plans.
2.7.7.2 For loss of cooling to data center equipment due to a cooling support system equipment breakdown,
the overall objective of the ECP for this scenario is to shut down data processing equipment in an orderly
manner upon loss of cooling, or impending loss of cooling, before the temperature exceeds the facility’s or
the manufacturer’s guidelines, including warranty restrictions (i.e., thermal runaway).
For loss of cooling, the ECP should consider operations, sensors and alarms, and response capabilities of
emergency and operating personnel. Include the criticality of the data processing functions and an
understanding of the time available to become aware of developing overheating situations, make decisions,
and take actions to prevent data processing equipment damage from overheating.
2.7.7.3 In addition, evaluate the following elements in the contingency planning process specific to equipment
breakdown resulting in loss of cooling to data center processing equipment:
A. Data from the original equipment manufacturer’s (OEM) literature for all critical data processing
equipment components. Include warranty thresholds, recommended maximum short-term operating
temperatures, and automatic equipment shutdown interlocks provided by the OEM due to excess
temperatures in all data processing equipment (power supplies, servers, data storage equipment, etc.).
B. Calculations by qualified design professionals involving the nature of the cooling equipment, the room
and surroundings, and data processing equipment, to determine the expected room temperature rate
of rise on loss of cooling, assuming continued operation of the data processing equipment.
C. The probable time to data processing equipment damage due to temperatures exceeding critical
thresholds. Include at least the following input: data processing equipment individual heating
characteristics, electrical power input to the data processing equipment room, data processing equipment
space volume and height, normal data processing equipment space operating temperature, any partial
cooling from the cooling equipment connected to standby power.
D. Using the information in A through C, develop the following scenarios, at a minimum, in the ECP at
several levels of temperature threshold alarms, with the mitigation actions to be taken at each level:
1. Short-term (~1 sec), medium-term (~1 min), and long-term (~1 hr) interruptions of utility power to the
entire facility (See 2.7.8 for Service Interruption Planning).
2. Breakdown of a single critical cooling system component, such as chillers, chilled water pumps,
condenser water pumps, cooling tower fans, air handler fans (e.g., bearing seize), cooling media
control valves (e.g., failing closed), cooling system local and centralized controls, variable speed
drives, and electric power (e.g., circuit breakers) for any of the above equipment.
3. Additional breakdown scenarios as needed based on a review of the facility’s unique design,
arrangement, and operation.
E. The time necessary to provide sufficient cooling to the data processing equipment space following
short-term power loss to the facility, followed by power restoration, to avoid data processing equipment
overheating damage. Include at least the following input: time to start standby power generators, cooling
equipment connected to the standby power and time to start cooling equipment (e.g., controls, chillers,
pumps, cooling towers, CRAH, etc.).
F. Guidance if initial mediation efforts are not successful and the data processing equipment space
temperature continues to rise, including interrupting power to the data processing equipment (e.g., main
power, emergency power, facility UPS, and equipment based UPS) in accordance with the data processing
equipment power isolation plan.
2.7.7.4 Implement the loss-of-cooling ECP using the following elements:
A. Training: Provide plan training to facility operations personnel and data processing equipment operations
personnel.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 38 FM Global Property Loss Prevention Data Sheets

B. Authority: Designate at least one person per shift to have the authority to implement the ECP including
the data processing equipment power isolation plan (Section 2.7.2), if data processing equipment
shutdown is needed to prevent damage.
C. Operation: Designate personnel on each shift to perform the steps in the loss of cooling equipment
contingency plan.
D. Practice:
1. Review, test, and validate the loss-of-cooling equipment contingency plan at least annually to confirm
efficacy.
2. Practice recovering cooling to the data processing equipment, including starting emergency
generators, shifting critical equipment operation to backup (N+1) components, restarting HVAC
equipment (CRAH, chillers, pumps, cooling towers, controls, etc.).
3. Practice the real-time decision path in identifying situations in which cooling cannot be restored before
the data processing equipment incurs critically high temperatures, resulting in the decision to shut
down the data processing equipment.
4. Practice the actions required to interrupting power to the data processing equipment in accordance
with the power isolation plan to ensure the required timeframe is met.
2.7.7.5 Review and validate the ECP annually and when there are significant changes on site to manage
change and confirm efficacy of the plan.

2.7.8 Service Interruption Plan

2.7.8.1 When the loss of utility and/or support system services for a data center results in an unplanned
outage to site processes and systems considered key to the continuity of site operations, develop and
maintain a documented, viable service interruption plan (SIP).
To develop the data center SIP, conduct a systematic, strategic assessment of data center utilities and support
system services to identify in advance the impact of and response to loss of the services. Consider recovery
from damage to utilities and support system equipment, and impact of the loss of the process/equipment
operating conditions and environment. Consider the timeline for an orderly shutdown and isolation of
equipment per the documented emergency operating procedures and the power isolation plan, evaluate the
state of the equipment and then restart and restore full operations per the documented standard operating
procedures.
2.7.8.2 The data center SIP includes recovery options/mitigation strategies to respond to and recover from
the loss of services to mitigate the exposure. In addition, evaluate the following elements in the SIP process
specific to data center utility system electrical services:
A. Electrical service (see 2.8.1)
1. System design/redundancy for critical electrical paths
a. Single points of failure
b. Critical load flexibility, continuity
c. Power isolation
d. Outage duration: Short-term (~1 sec), medium-term (~1 min), and long-term (~1 hr)
interruptions of utility power to the entire facility
2. Capabilities, viability of the emergency power system
a. Emergency or standby generators
b. UPS
c. Orderly shutdown
d. Duration of operation
e. Fuel supply/replenishment for expected duration
B. Loss of cooling due to loss of electrical service (see 2.8.3)
1. System design/redundancy for critical cooling paths

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 39

2.7.8.3 Review and validate the SIP annually and when there are significant changes on site to manage
change and confirm efficacy of the plan.

2.8 Utilities and Support Systems

2.8.1 Electrical Distribution System

Data centers rely on stable uninterrupted electrical power. The performance goals for the electrical distribution
system are as follows:
A. The electrical distribution system must be designed with sufficient redundancy so that the failure of a
single piece of equipment will not result in the interruption of a large portion of the data processing
capabilities of the data center.
B. The power quality of the electrical distribution systems must meet the requirements of the utilization
equipment.
C. For critical data centers, sufficient emergency/standby power must be provided to allow operation of
the data center without utility power.
D. The design of the electrical distribution system must allow for the inspection, testing and maintenance
of the major components. Special attention may be needed when designing uninterruptable power
supplies, automatic transfer switches, and emergency power systems to allow functional testing and
maintenance of these devices without interrupting operations.
E. Design the electrical distribution system to limit voltage dips at sensitive equipment due to faults in
the electrical equipment. This can be accomplished using current limiting fuses, fast acting trip devices,
uninterruptible power supplies (UPS), Continuous Power Supplies (CPS), or other means.

2.8.1.1 Electrical Power System Studies

2.8.1.1.1 Perform the following studies in accordance with International Testing Association’s Standard for
Acceptance Testing Specifications (NETA ATS), or other recognized equivalent standard, for new construction
or when major additions are made:
A. Short-Circuit Study
B. Coordination Study
C. Arc-Flash Hazard Analysis
D. Load-Flow Study
E. Stability Study

2.8.1.2 Electrical Utility

2.8.1.2.1 Provide a reliable source of power to the data center.
2.8.1.2.1.1 Have a qualified engineering firm perform a regional power supply reliability study as part of the
site selection process for a new data center facility.
A. Focus the study on the number, duration, and cause of major system outages to the proposed site
over a minimum 10-year period.
B. Consider future load growth and the utility’s plans to address the growth.
2.8.1.2.2 Provide a minimum of two independent utility feeds to the facility’s main substation. (See Figure
2.8.1.2.2 for examples.) Arrange the utility feeds as follows:
A. Supply each feed from a separate substation. Establish power supply from substations that are as
electrically independent as possible.
B. Arrange the utility’s protective scheme so that a fault in one substation or feed will not cause the tripping
of the other substations or feeds to the facility.
C. Arrange each feed so there is no single event, such as a substation fire, vehicle collision, wildland
fire, or excavation, that will affect more than one feed.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 40 FM Global Property Loss Prevention Data Sheets

D. Where the utility feeds enter the main facility substation, provide a fire-resistive cable coating on all
critical cables to ensure a single fire event does not affect more than one feed.
E. Size the feeds so the facility can meet its entire power requirement with one feed out of service.
F. Provide adequate lightning protection and surge protection for each feed in accordance with Data Sheet
5-11, Lightning and Surge Protection for Electrical Systems.

U2
U1

Normally
Open

U1main ER1 ER2 X-Conn ER3 ER4 U2main

Utility Main Switchgear

Normal medium voltage (MV) switchgear will usually have
two sides. In this figure is a cross-connect breaker, or bus
tie breaker. It is normally in the “normally open” position.
This connects the two switchgear sides to each other, in
the event one of the utility feeds goes down.

Ideal
Each utility feed is fed from a separate sub-station. Each
substation is fed from an independent master sub-station.
Alternate
Each utility feed is fed from a separate sub-station, but
both tie back to the same master sub-station with separate
feed lines.
Fig. 2.8.1.2.2. Utility Main Switchgear

2.8.1.3 Electrical Distribution System operating at or over 1,000 V.

2.8.1.3.1 Incorporate the following into the distribution system:
A. Provide a minimum of N+1 transformers at the HV and MV level.
B. Arrange the transformers to have adequate separation in accordance with Data Sheet 5-4,
Transformers.
C. Arrange the control/protection systems so that they are not subject to a common impairment.
D. Arrange the distribution system so the full demand of the site can be supplied with any one component
of the system out of service for maintenance or repair. Ensure the design of the distribution system
considers heating from harmonic distortion due to non-linear loads, if required.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 41

E. Arrange feeders from the substation(s) to the equipment so an impairment in one run will not affect
the other runs:
1. Encase underground conduits in concrete and place a tracer/warning tape above the conduits.
Common splice vaults should not be used. If splices in the underground run are unavoidable, a
separate splice vault should be used for each conduit.
2. Feeders should not be run in a common underground tunnel unless provisions are provided to prevent
a fire in the tunnel from affecting multiple feeders.
3. Feeders run on overhead lines should be run on separate power poles and routed to prevent a
common impairment from affecting multiple feeders.
F. Provide electrical protection in accordance with the applicable FM Global data sheets.
G. Provide lightning and surge protection for power supplies to data center systems in accordance with
Data Sheet 5-11, Lightning and Surge Protection for Electrical Systems.

2.8.1.4 Electrical Distribution System operating below 1,000 V.

2.8.1.4.1 Arrange the distribution system so the data center and support equipment can be supplied with a
single distribution transformer, distribution cable, main breaker, or tie breaker temporarily out of service.
2.8.1.4.2 As required, arrange the design of the distribution system to mitigate heating from harmonic
distortion due to non-linear loads.
2.8.1.4.3 Emergency/Standby Power Generators
2.8.1.4.3.1 Provide sufficient on-site generation so that the data center operations will be unaffected by a
loss of utility power. See Figure 2.8.1.4.3.1.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 42 FM Global Property Loss Prevention Data Sheets

U2
U1

Normally
Open

U1main ER1 ER2 X-Conn ER3 ER4 ER-E U2main

Each electrical room is fed ATS* ATS* ATS* ATS* ATS*

from a utility side, with a MAINS MAINS MAINS MAINS MAINS

dedicated generator.
UPS UPS UPS UPS UPS
Bypass Bypass Bypass Bypass Bypass

UPS w/ UPS w/ UPS w/ UPS w/ UPS w/

Mechanical

Mechanical

Mechanical
Mechanical
Mechanical

SWBD

SWBD

SWBD
SWBD
SWBD
STS STS STS STS STS

Suite 1 (dedicated), Generator 1

Open transition, ~10-15 secs.
(X3) 30 sec. timer attempts UPS UPS UPS UPS UPS
SWBD SWBD SWBD SWBD SWBD
before using SWING 12

STS

Distributed Redundant
This design utilizes half of the electrical room assets of the A&B
redundant design, and “weaves” or distributes the critical UPS
power in different ways to the data center of data hall.

This design is now commonly used at very large data halls.

For this design, the UPSs are N+1, vice 2N found in the A&B
redudant design.

2N vs. N+1
N+1 represents “nominal” (or normal full load), plus a redundant unit.
It can also be used to share load to reduce “wear and tear” and
extend end of life (EOL).
2N represents a duplication of N+1, which is common for the A&B
redundant POD design.

* The ATS function is typically accomplished using PLC control of the

Main and Generator circuit breakers.

Fig. 2.8.1.4.3.1. Distributed Redundant Power

2.8.1.4.3.2 Locate diesel generators and fuel supplies in accordance with Data Sheet 5-23, Design and
Protection for Emergency and Standby Power Systems and Data Sheet 13-26, Internal Combustion Engines.
2.8.1.4.3.3 Provide one of the following fuel supplies for the generators, listed in order of preference:
A. A fuel supply to last 24 hours.
B. A documented service interruption plan (SIP) that specifies the generators are to be refueled at a rate
that allows uninterrupted operation of the generators for 24 hours.
2.8.1.4.3.4 Provide fire detection and protection in accordance with recommendations for fuel storage, fuel
piping, and diesel generator protection in Data Sheet 5-23, Design and Protection for Emergency and Standby
Power Systems.
2.8.1.4.3.5 To prevent accidental use, permanently cap old fuel lines to diesel fuel tanks if no longer
connected.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 43

2.8.1.4.3.6 When work is performed on fuel lines or fuel filters, use lock-out tag-out procedures on fuel pumps
supplying fuel to diesel generator day tanks to prevent accidental starting of pumps and discharge of fuel
while the area is unattended.
2.8.1.4.3.7 Provide noncombustible soundproofing materials when soundproofing materials are required.
2.8.1.4.4 Uninterruptible Power Supply (UPS)
2.8.1.4.4.1 Where battery UPS system are provided, design, locate and install the system in accordance
with Data Sheet 5-28, DC Battery Systems.
2.8.1.4.4.2 Provide UPS power for data center systems susceptible to power fluctuations when the interruption
of the system may result in significant business interruption or financial loss. See Data Sheet 5-23, Design
and Protection for Emergency and Standby Power Systems.
2.8.1.4.5 Battery back-up units (BBU)for Distributed Power Systems
2.8.1.4.5.1 When battery back-up units (BBU) (see Section 3.4.1.2) are used in the data processing equipment
room, provide them to meet the following conditions:
A. Limit the maximum power capacity of 20 kWH per server rack. See section 3.4.1.2 for calculating power
capacity.
B. No more than 2 shelves containing BBU modules should be located together in the same area of the
rack. (see Figure 2.4.4.1 for typical configuration)
2.8.1.4.5.2 Server racks with Li-ion Battery Back-up Units (BBU) exceeding the maximum capacity of 20
kWh per rack should be considered Energy Storage Systems (ESS) and the recommendations as identified
in Data Sheet 5-33, Energy Storage Systems, are to be followed.

2.8.2 Power Isolation of Data Processing Equipment and HVAC Systems

The goals of the recommendations for the power isolation of data processing equipment and HVAC systems
are to remove the potential for reignition and minimize the circulation of smoke to sensitive electronic
equipment. These goals are further explained in section 3.4.4.
It is recognized that the installation of a power disconnect system to rapidly isolate power and HVAC supplies
can seem contrary to the critical power/business continuity requirement of most data centers. However, it
should also be recognized that an electrical fault is the most probable fire ignition source in a data center.
To ensure adequate control of fire propagation, prevent reignition and allow emergency response personnel
access, it is necessary to have a way of reliably isolating power.
Although there is a relatively high level of electrical fault protection throughout a data center via circuit
breakers, fuses or other means, these cannot be relied upon to de-energize the faulty equipment and remove
the ignition source. Some of the scenarios where electrical protection could fail to clear an electrical fault
and remove the ignition source are included in Section 3.4.2.2.

2.8.2.1 Power Isolation Method

2.8.2.1.1 Provide a power isolation method to achieve the following (separately or together):
A. De-energize all electrical power to the data processing equipment in the room or designated zone(s),
except power to lighting, in the event of sprinkler, water mist system, and/or clean agent fire extinguishing
system operation.
B. When appropriate, de-energize all dedicated heating, ventilation, and air-conditioning (HVAC) systems
for the data processing equipment serving the room or designated zone(s), as appropriate, in the event
of sprinkler, water mist system, and/or clean agent fire extinguishing system operation. See Section 2.8.3
for further guidance on the impact of power isolation to HVAC equipment.
2.8.2.1.2 Provide the appropriate power isolation method based on the type of fire protection installed and
site conditions as follows (the critical goal is to achieve power isolation before the end of the fire protection
agent duration):
A. For areas protected by a wet or preaction sprinkler system in accordance with the recommendations
of Section 2.4.7.1, or a water mist system in accordance with the recommendations of Section 2.4.7.2,
provide one of the following, listed in order of preference:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 44 FM Global Property Loss Prevention Data Sheets

1. Automatic power isolation

2. Manual power isolation in accordance with Section 2.7.2
B. For areas protected by only a clean agent fire extinguishing system, provide one of the following, listed
in order of preference:
1. Automatic power isolation
2. Automatic power isolation with a time-delay (see Section 3.4.4)
3. Manual power isolation in accordance with Section 2.7.2 if all the conditions for manual power
isolation listed in Section 2.8.2.1.4 are met.
2.8.2.1.3 If abrupt power isolation will damage data processing equipment, use a controlled shutdown of
the data processing equipment prior to isolation of the power source.
2.8.2.1.4 If the need for business continuity provided by the data processing equipment prevents the use
of automatic power isolation, a manual power isolation method and plan as recommended in Section 2.7.2
is acceptable for areas protected by only a clean agent fire extinguishing system if it can be relied on in all
situations and is evaluated to be equivalent to automatic power isolation. All of the following conditions must
exist in order to accept manual power isolation:
A. VEWFD system is provided in all equipment rooms in accordance with recommendations of Section
2.4.6.
B. VEWFD alarms are monitored at a constantly attended location and alarms are immediately
communicated to emergency responders. In addition, alarms may be instantly communicated to
emergency responders via notifications to their mobile device.
C. Qualified and highly trained emergency responders are on site 24 hours per day and are knowledgeable
of all power sources and the methods of isolating power to data center equipment, beginning as localized
as conditions permit. Responders should be authorized to execute the emergency power isolation plan
as needed. Response should be prior to the activation of fire protection systems.
D. The data processing equipment room ceiling/roof and walls (not including hot/cold aisle partitions) are
of noncombustible construction in accordance with Sections 2.2.2, 2.2.3, 2.2.5, and 2.5.6.
E. Excellent human element programs are established and implemented:
1. Fire protection system impairments are well managed.
2. Ignition sources are controlled.
3. Maintenance, testing, and inspection of fire protection and detection systems are regularly completed.
4. Penetrations to data processing equipment rooms are properly maintained.
5. Electrical maintenance, testing, and inspection are regularly completed.
6. Housekeeping is excellent.
7. An emergency response plan is in place that includes data processing equipment overheating, smoke
detection, and manual fire extinguishing equipment operation response.
F. The power isolation plan is:
1. agreed upon by senior site management,
2. reviewed at least quarterly, and
3. tested or drilled at least annually by all individuals involved in the plan.
G. The time to complete the manual power isolation should be measured in each annual test/drill. It should
be within a maximum of 10 minutes after the fire detection alarm is received and take into account any
possible power-isolation authorization request procedure that could exist at the facility. The test/drill should
confirm that the plan is in accordance with Section 2.7.2.3.
Reference Data Sheet 4-9, Halocarbon and Inert Gas (Clean Agent) Fire Extinguishing Systems on
Acceptance of Installations for determination of duration of protection.

2.8.3 Heating, Ventilation, and Air Conditioning (HVAC)

Provide heating, ventilation, and air-conditioning (HVAC) systems in accordance with Data Sheet 1-45,
Air-Conditioning and Ventilation Systems, Data Sheet 7-13, Mechanical Refrigeration and the
recommendations in this section.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 45

A. Reliability
Provide minimum N+1 online redundancy for HVAC components required to maintain the data processing
equipment space environmental conditions (e.g., temperature, relative humidity) required for normal
operations, such as fans, air handling units (AHU), computer room air-handling (CRAH) units, computer room
air-conditioning (CRAC) units, chillers, cooling towers, pumps, controls, humidification system components,
etc.
B. Forced Air Distribution Systems
1. Provide air-handling equipment and air flow paths (e.g., AHUs, ducts) that are independent from those
connected to other building spaces.
2. If is it not physically possible to provide air-handling equipment and air flow paths that are independent
from those connected to other building spaces, do the following:
a. Provide smoke dampers in ducts into the data processing equipment space such that closure isolates
the data processing equipment space from supply, return, or exhaust airflow in the remainder of the
building.
b. Provide listed smoke dampers with maximum leakage per Leakage Class II per UL 555S Standard
for Smoke Dampers. Where smoke dampers are located at fire rated partitions, provide combination
fire and smoke dampers rated per both UL 555S and UL 555 Standard for Fire Dampers.
3. Provide a positive pressure of at least 0.05 in. (3 mm) water gauge in the data processing equipment
rooms relative to adjacent areas.
4. Interlock forced cooling air ventilation to reduce the ventilation air velocities to less than 5 ft/sec (1.5
m/s) upon activation of the pre-alarm condition for the VEWFD system.
a. Design forced air distribution systems using Computational Fluid Dynamics (CFD) modeling or
equivalent design technologies to determine the ventilation air velocity and determine the need of an
interlock to reduce the forced cooling air ventilation velocity with detection.
b. Measure maximum air velocities in the commissioning phase of the data center to confirm the
ventilation air velocity.
i. Horizontal velocity is to be measured along the length of the aisle at heights of 5 ft (1.5m) from
floor, at the midpoint of horizontal cable tray(s) height, and within 4 and 10 in. (0.1 and 0.25m)
from the ceiling.
ii. Measure multiple locations along the length of the server rack aisle.
iii. Horizontal velocity should not be measured in close proximity to fan walls as it is expected these
velocities will be higher but measured no further than at the leading edge of the server racks from
the fan wall.
c. Conduct an acceptance test of the interlock(s) in accordance with Section 2.6.3.4 to confirm reduction
of air velocities to less than 5 ft/s (1.5 m/s) in the commissioning phase.
i. Test interlocks regularly in accordance with section 2.6.2.B.
ii. Keep documents on file for review during regular loss prevention visits.
C. Liquid Systems
1. Keep chilled water piping connected to air-handling and other cooling equipment controlling the data
processing equipment space environment separate from chilled water piping serving the remainder of the
building.
2. Do not route chilled water piping that provides cooling to building spaces other than the data processing
equipment space through the data processing equipment space envelope.
3. Connect dedicated data processing equipment space piping as close as possible to the chilled water
source, arranged in a loop with valves capable of dual feeding air handlers in the event of a pipe failure for
critical applications.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 46 FM Global Property Loss Prevention Data Sheets

4. Do not locate HVAC liquid piping, including chilled water, hot water, humidification, and drains, above
data processing equipment spaces.
5. Provide leak detection with alarm for water piping at air-handling units (AHU).

2.8.3.1 Controlling HVAC Systems

A. Provide HVAC control systems, e.g. proportional-integral-derivative (PID) algorithm program with controls
to provide an alarm if the setpoint error and the historical rate of room temperature change indicate an
impending overheating event.
B. Provide alarms to initiate mitigation actions based on several levels of temperature thresholds.
1. High temperature: No more than 2°F or 2°C above the normal setpoint operating temperature of the
lower of either (a) the high data processing equipment temperature (as recommended by the OEM)
measured at the equipment, or (b) the high space air temperature setpoint per the facility HVAC design.
2. Rate of temperature change: As a result of the study recommended in the loss-of-cooling equipment
contingency plan (see 2.7.7.1).
C. Provide audible and visual alarms in the vicinity of the equipment and at a constantly attended location.
D. Provide emergency power to HVAC systems (e.g., fans, CRAHs, chillers, cooling towers) for data
processing equipment spaces.
E. Provide battery or an alternative power backup such as capacitors for HVAC controls.

2.8.3.2 Monitoring HVAC Equipment

A. Provide HVAC system equipment with sensors to detect equipment operation or failure. Automatically
initiate alarms, remedial actions, and start redundant (N+1) equipment. Measure the temperature or
movement of the subject media directly (i.e., do not sense only electric motor failure). At a minimum, include
the following:
1. Air handler supply duct airflow and temperature
2. Chilled water flow and temperature
3. Condenser water flow and temperature
4. Thermal storage systems
5. Evaporative cooling
6. Economizers
7. Refrigerant flow and temperature (especially for direct rack cooling)
8. Failure of electric power to this equipment
B. Initiate loss of electrical power or data processing equipment controls to activate alarms or actions to sense
and mitigate data processing equipment space overheating. (See Section 2.8.2)
C. Install sensors inside data processing equipment or equipment racks to detect abnormal equipment
operation or overheating.
D. Provide temperature sensors associated with the data processing equipment space HVAC controls (e.g.,
wall mounted temperature sensors and thermostats) or the building automation system software connected
to those sensors.
E. Provide separate temperature sensors that are independent from the HVAC controls if the HVAC sensors
or controls are not configured for communication with alarms, electrical power controls, or data processing
equipment controls.

2.8.3.3 HVAC System Commissioning

Do not operate data processing equipment during or following the installation of new HVAC equipment or
controls, or the modification of existing HVAC equipment or controls, without fully commissioning the systems
to demonstrate proper operability across the full range of functions. This includes testing automatic interlocks
and controls associated with abnormal conditions or system malfunctions. Include data processing equipment
high-temperature alarms and actions, and data processing equipment space high-temperature and excessive
rate of temperature rise alarms and actions.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 47

2.8.3.4 Filters
Provide heating, ventilation, and air-conditioning (HVAC) filters that are listed to Underwriters Laboratories
(UL) Standard 900 for fire performance.

2.8.3.5 Smoke Management Systems

2.8.3.5.1 If a smoke management system is to be installed, retain a competent and experienced firm to design
the system in accordance with site-specific performance goals.
2.8.3.5.2 When installed, design smoke management systems to include the smoke control and removal
recommendations identified in Data Sheet 1-45, Air -Conditioning and Ventilating Systems.

3.0 SUPPORT FOR RECOMMENDATIONS

3.1 Construction and Location

3.1.1 General
Data centers are complex facilities with both active and passive fire protection systems, along with critical
support equipment to keep the facility operational. A total building commissioning program may be warranted
to assist in the quality control for construction and operational functionality of the occupancy. The following
documents provide guidance in the development of a commissioning program:
• NFPA 3, Recommended Practice for Commissioning and Integrated Testing of Fire Protection and
Life Safety Systems
• NFPA 4, Standard for Integrated Fire Protection and Life Safety System Testing
• American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
Commissioning Guideline 0-2005.
Data centers located below-grade are susceptible to water ingress (surface, storm, and/or flooding).

3.1.2 Penetrations
The objective of sealing penetrations is to prevent smoke from a fire in adjacent spaces from entering the
data processing equipment space, and to hold a clean agent concentration, if applicable.
Fire-resistance-rated penetration seals do not prevent the passage of smoke until the seal expands when
exposed to heat from the fire. A penetration seal with a leakage rating will limit the passage of smoke before
the seal is exposed to high temperatures. Laboratory leakage tests are conducted at ambient and at 400°F
(204°C).

3.1.3 Cables
Cables listed to UL 910 are marked with an identification code.
Power cables and junction boxes for power cables with chlorinated polyethylene or polyvinyl chloride (PVC)
sheathing, insulation, or construction when involved in a fire or electrical fault could produce hydrochloric
acid (HCL) gas at levels sufficient to produce smoke damage and corrosion to the data processing equipment
and other equipment.

3.1.4 Insulation
For moisture/condensation control reasons, elastomeric and neoprene rubber are sometimes placed on the
underfloor of the raised floor space.

3.1.5 Earthquake
Earthquake requirements and testing for telecommunications equipment are described in NEBS
Requirements: Physical Protection, Telcordia Technologies GR-63-CORE. Equipment is not listed or labeled,
so it cannot be determined whether equipment has been tested to these requirements.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 48 FM Global Property Loss Prevention Data Sheets

The NEBS standard is based on testing the equipment using a synthesized waveform and earthquake
response spectra for the purposes of confirming equipment functionality as well as overall restraint of the
equipment cabinet/rack.

3.2 Protection

3.2.1 General
A. Aerosol Generator Fire Extinguishing System Units
Aerosol generator fire extinguishing system units are not clean agent systems as defined by Data Sheet
4-9, Clean Agent Fire Extinguishing Systems. Some products are thermally actuated, so they would not
provide equipment protection in accordance with FM Global recommendations for this type of occupancy,
even if used with sprinkler protection.
Those products that are listed by Underwriters Laboratories have specified limitations associated with the
product category. In particular, they are intended for total flooding applications of normally unoccupied or
uninhabitable spaces and the potential effects of aerosol extinguishing agent discharge residue on sensitive
equipment and other objects have not been investigated.
B. Oxygen Reduction Systems
An oxygen reduction system (ORS) is a fire protection system in which combustible materials are protected
by actively maintaining lower oxygen concentration than that in normal air by specialized conditioning
equipment.
FM Global has conducted research on the subject of material flammability in reduced oxygen environment
(Xin and Khan, 2007). The results show that many commonly used materials such as wood, plastics and
fabrics can burn at an oxygen level below 12% by volume. Since this oxygen level is not only expensive
to actively maintain, but also beyond the range of human health requirements without using specialized
procedures, oxygen reduction systems are not recommended to replace sprinklers as the primary means of
fire protection or as a special protection system for equipment.

3.2.1.1 Portable Fire Extinguishers

Portable clean agent fire extinguishers typically in the 10-15 lb (4.5-6.8 kg) capacity, or Class “A” and Class
“C” using the NFPA 10, Standard For Portable Fire Extinguishers, classification and rating number system,
for energized electrical fires in electrical and electronic equipment in the data processing equipment and
service rooms fulfill the recommendation in Section 2.4.2.
Portable carbon dioxide fire extinguishers may not be effective because the cable insulation is considered
a combustible or Class “A” material. Portable carbon dioxide fire extinguishers are not rated for this hazard.
In considering whether the typical capacity of the fire extinguisher for an energized electrical fire needs to
be increased or decreased, the following items should be evaluated:
• Size of the electrical equipment
• Configuration of the electrical equipment that influences distribution of the extinguishing agent
• Effective discharge range of the fire extinguisher
• Amount of combustible material involved (Class A per NFPA 10)
• Installation of a clean agent fire extinguishing system for protection of the electrical equipment
De-energizing electrical equipment eliminates the potential for an arcing hazard if the portable fire extinguisher
accidentally comes into physical contact with the energized equipment or brings any conductive part within
arcing distance.
A 2-1/2 gal (9.5 L) water or clean agent portable fire extinguisher (2-A rating per NFPA 10 classification and
rating) for areas containing even limited amounts of ordinary combustibles is appropriate.
The travel distance of 75 ft (23 m) is based upon an ordinary (moderate) level of combustibles, such as paper
and plastics. The travel distance may be decreased to improve accessibility of the portable fire extinguisher
for protection of the electrical equipment.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 49

Dry chemical extinguishers should not be used on electrical or electronic equipment and should not even
be present in a data processing equipment room. The dry chemical extinguishing powder is corrosive to
electronic circuitry. If such an extinguisher was discharged in an area containing electronic equipment, drifting
of the very lightweight powder would likely result in the need to clean/recondition all of the equipment in the
area.

3.2.2 Data Processing Equipment Rooms

The type of fire detection and fire protection system chosen should be based upon an evaluation of the
complete occupancy. The level of protection should consider, at a minimum, the building construction and
contents, building infrastructure, equipment materials of construction, and exposures.

3.2.3 Raised Floor and Above-Ceiling Areas Containing Cable

FM Approved water mist systems listed specifically for protection of cables below raised floors have two
different design methods: (1) area of coverage and (2) local application. The area of coverage design uses
a square nozzle spacing throughout the entire below raised floor area regardless of cable tray location. The
local application design uses linear spacing and is intended to protect the specific length of cable tray. Either
design can be used alone or in conjunction with the FM Approved “above-floor protection” design. The FM
Approval listing for below raised floor protection will designate the number of cable tray tiers it has been
evaluated to adequately protect.

3.2.4 Detection
3.2.4.1 Very early warning fire detection (VEWFD) systems detect smoldering or off-gassing typically
generated from an overheating condition or from low-energy fires. VEWFD systems detect incipient fires in
critical areas before flame or even noticeable smoke develops. VEWFD may use aspirating (air-sampling
detectors) or high-sensitivity, intelligent, spot sensor/detectors. Detectors used to accomplish VEWFD are
listed as being capable of providing alarm initiation at threshold levels that are more sensitive than
conventional smoke detectors.
3.2.4.2 For aspirating smoke detectors and intelligent high sensitivity spot smoke detectors, typically, multiple
smoke level thresholds can be used to perform a progressive response to a potential fire that minimizes
business impact:
• Level 1 (Alert): Notify constantly attended location.
• Level 2 (Pre-Alarm/Action): Local alarm in protected area; initiate data transfer (re-route data to alternate
data center equipment room or data center), interlock of reduced ventilation rate.
• Level 3 (Alarm/Fire): Initiate fire alarm to building fire alarm control panel and fire service, initiate
suppression (or interlocked preaction sprinkler system or stage one on a double-interlock system).
Typical minimum alert and pre-alarm settings for air-sampling systems are usually 0.2%/ft (0.7%/m)
obscuration (effective sensitivity at each port). Alarm settings for air-sampling systems are usually 1.0%/ft
(3.3%/m) obscuration (effective sensitivity at each port).
3.2.4.3 For intelligent high-sensitivity spot smoke detectors the obscuration sensitivity levels can be
programmed similar to an aspirating smoke detector. The control panel used with an intelligent high-sensitivity
spot smoke detector, typically, has fewer levels of notification with a reduced progressive response.
3.2.4.4 Obscuration sensitivity levels for an air-aspirating smoke detector is programmed by software at the
VEWFD control panel. Programmed obscuration levels should be verified for acceptance from submitted
plans. Propriety methods (e.g., a lap-top computer or portable handheld device with software) are available
from the VEWFD manufacturer and require the installer/service person to assist in the validation. In some
cases an auxiliary system monitor is used that allows the obscuration levels to be directly verified.
3.2.4.5 When evaluating the use of aspirating smoke detection versus intelligent high-sensitivity spot smoke
detection, the specific requirements for the occupancy need to be considered, including the following:
• Progressive response notification
• Local identification of the event
• Type of fire protection system(s) provided
• Number of fire protection systems and/or zones provided

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 50 FM Global Property Loss Prevention Data Sheets

3.2.4.6 The location of the smoke detectors or sensors should be based on an engineering survey of the
area to be protected. Factors such as air flow, proximity to air handling system diffusers, and other physical
features of the installation need to be taken into account.
Smoke tests can be run to verify the air flow within the protected area favors the smoke detectors. Testing
should be performed with all racks, servers, and other support equipment in full operation. In addition, it is
important to have the HVAC running at normal capacity. The heat generated from the server racks and
subsequent air movement from them and the HVAC will impact smoke stratification and VEWFD response
and obscuration readings.
Extension of ceiling spot detectors or sensors downward into the flow path of sheared air (using photoelectric
units to prevent false alarms) or providing individual addressable sampling ports to the specific server cabinet
rack should be considered where strong ventilation currents cause air at the ceiling to remain relatively
stagnant or identification of the event is critical.
Additional general guidance on the placement of detectors can be found in the following documents:
• Data Sheet 5-48, Automatic Fire Detectors
• ANSI/NFPA 72, National Fire Alarm Code
• FM Global Research Technical Report, Experimental Data for Model Validation of Smoke Transport in
Data Centers
Dilution of smoke can occur within a large room and high air flow, do not exceed the recommended spacing
in Section 2.4.5.1.
3.2.4.7 A series of tests was carried out in 1998 by one of the leading telephone companies to compare
the effectiveness of various types of fire detection systems in electronic communication equipment areas.
It was found that the aspirating VEWFD system detected all of the materials burned, including tests in which
material was burned within the frame. The latter could not be detected by any other detector used. The
projected beam detector was able to detect all fires outside of the equipment frames. The time to detection
was roughly comparable to the most sensitive standard spot-type smoke detector.
The lack of one feature was considered important for standard spot-type detectors. This feature was the
ability to set the detector at more than one alarm point; for example, an aspirating VEWFD detector can be
set for a multiple number of pre-alarm points before the detector actually alarms. The one photoelectric
standard spot detector tested alarmed in still air and under all of the air flow conditions tested for all of the
materials tested. Some types of ionization spot detectors performed better than others. The ionization
detectors did not detect some plastics fires. They also did not detect some fires where the air flow was from
below the floor or when air flow was from ceiling-mounted diffusers to a low exit point.
3.2.4.8 Ambient temperatures in a hot aisle could be in the range of 100°F (38°C) or more, which may be
the maximum or in excess of the operable temperature for the detector.
3.2.4.9 The use of a time delay is to allow for the evacuation of personnel from the protected area/room
for actuation of a special protection system.

3.2.4.10 Portable Detection

Supplementing fixed smoke detection with portable detection is recommended to identify a localized event
from the zone in which it is identified in order to provide localized power isolation and/or extinguishment. Two
portable handheld devices typically used for this purpose are the aerosol monitor and the thermal imaging
device. The aerosol monitor uses a light-scattering laser photometer that isolates contaminants in the optics
chamber to measure concentrations that can be set to correlate to the fixed smoke detection. The handheld
thermal imaging device is used to identify overheated components.

3.2.5 Suppression

3.2.5.1 Automatic Sprinkler Systems

Install wet pipe sprinklers versus pre-action sprinkler systems whenever possible. Pre-action sprinkler
systems are inherently less reliable than wet sprinkler systems due to the significantly higher levels of
inspection, testing, and maintenance required. Closely examine the concerns with a wet-pipe sprinkler system
before installing an alternative.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 51

Table 2.4.7.1.2 describes the introduction of water into the sprinkler piping for wet, non-interlocked, single-
interlocked and double-interlocked sprinkler systems. Further detail is included in the Glossary of Terms for
each sprinkler system type.
In general the lower the room ceiling height the more effective the fire protection systems will be. The limit
on data center ceiling heights to 30 ft (9.1m) is intended to allow sprinkler protection to activate promptly
thereby reducing fire, smoke, and water damage. The ceiling height limitation also constrains the room
volume such that clean agent fire extinguishing system sizes and clean agent distribution remain practical.

3.2.5.2 Water Mist Systems

No general design methodology exists for water mist systems. Fire control performance is not consistent
between manufacturers of water mist systems. The characteristics of drop-size distribution, nozzle spacing,
spray angle, installation parameters, and other characteristics are determined from full-scale fire testing to
replicate a specific hazard application. Therefore, only an FM Approved water mist system listed for the
specific hazard application can provide acceptable protection.
The performance characteristics of water mist systems will differ based upon their design principle. A water
mist system could be low-pressure, single or dual fluid; or high-pressure, single or dual fluid. Do not
interchange the supply pump units on different model systems, even from the same manufacturer.
A dual fluid system in which the compressed air or nitrogen mixed with the water was integral in evaluating
the performance for fire extinguishment. Therefore, each supply pump unit needs to be used with its specific
model of water mist system.

3.2.5.3 Halocarbon and Inert Gas (Clean Agent) Fire Extinguishing Systems
3.2.5.3.1 Even if there is no cabling below the raised floor (or no air flow), the extinguishing agent will
eventually leak to the lowest point in the room, which is below the raised floor. If there is no extinguishing
agent discharged in the space below the raised floor, a dilute concentration will develop in the room. That
concentration may not be sufficient to provide extinguishment and may produce greater amounts of
extinguishing agent decomposition.
3.2.5.3.2 When protecting only the space below a raised floor, during and after a discharge, a portion of
the extinguishing agent under the raised floor will migrate into the room above it. If any fire is present in the
electrical equipment above the raised floor, the extinguishing agent would be at a level below the design
extinguishing concentration. If the extinguishing agent is a halocarbon, considerable decomposition of the
extinguishing agent could occur, and additional contamination may result from it.
3.2.5.3.3 Where a second smoke detector actuation or alarm 2/second-level alarm will result in discharge
of a total flooding halocarbon or inert gas (clean agent) fire extinguishing system, operating procedures should
specify that all nonessential personnel evacuate the area/room. This will prevent the unfavorable situation
of personnel exiting through a door after the fire extinguishing agent discharge has begun. Continuous
opening of exit door(s) during or after the discharge will allow some of the extinguishing agent to escape,
possibly causing the concentration in the protected area/room to drop below levels needed for fire
extinguishment.
3.2.5.3.4 Always label and differentiate fire alarm pull stations and emergency power-down controls to avoid
confusion.
3.2.5.3.5 When using an abort switch for halocarbon or inert gas (clean agent) fire extinguishing systems,
the choice of location should consider the ability of the operator to be aware of any changes in conditions for
the protected area/room.
3.2.5.3.6 Halocarbons or inert gas (clean agents) discharged from the nozzle require a certain length of
distance to vaporize. If the clean agent comes in contact with a surface, e.g. cable trays, containment system
walls, obstructions, before the clean agent is vaporized, frosting can occur. This will result in a delivered
concentration less than the design concentration for protection of the room and/or enclosure.
3.2.5.3.7 Very short discharge times (less than 60 seconds) should not be used with inert gas fire extinguishing
systems if hard disk drives are susceptible to disruption of performance by sound pressure levels (e.g. noise)
from the discharge. A minimum 30-second discharge time is part of the FM Approval listing, but should be
avoided for this occupancy.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 52 FM Global Property Loss Prevention Data Sheets

3.3 Equipment and Processes

3.3.1 Servers, Mainframes, and Supercomputers

3.3.1.1 Nationally recognized testing laboratories (NRTLs) that evaluate equipment to electrical safety
standards include the following:
• Underwriters Laboratory (UL)
• Intertek
• VDE Testing Institute
• TÜV
Electrical safety standards that help reduce the risks of fire, or arcing with equipment include the following:
A. Underwriters Laboratories (UL)
• UL 478, Standard for Electronic Data-Processing Units and Systems
• UL 1950, Standard for Safety of Information Technology Equipment
• UL 60950, Safety of Information Technology Equipment
• UL 60950-1, Information Technology Equipment - Safety - Part I: General Requirements
B. British Standard Institute (BSI)
• BS EN 60950-1:+A12 Information technology equipment. Safety. General requirements.
3.3.1.2 Where signs of inadequate single-point grounding have been observed, a qualified electrician or other
qualified consultant should study the installation, and appropriate diagnostic and corrective actions should
be taken. See Data Sheet 5-20, Electrical Testing, for symptoms of inadequate grounding.
Further detailed grounding information (design and installation) can be obtained from IEEE 1100 1992,
Recommended Practice for Powering and Grounding Sensitive Electronic Equipment.
3.3.1.3 Servers
A server is a piece of data processing equipment, computer, or device (see Figure 2.5.1.1.2) that manages
network resources. Servers are the backbone of the internet. They serve up information in the form of text,
graphics, and multimedia to online data processing equipment that request data. A blade server is designed
for high-density computing.
3.3.1.4 Mainframes
Mainframes are powerful computers used primarily by corporate and government organizations for critical
applications, bulk data processing, industry and consumer statistics, search function capability, and financial
transaction processing. The term originally referred to large cabinets that housed the central processing unit
and main memory of early computers.
3.3.1.5 Supercomputers
Used in the sciences, engineering, defense intelligence, weather forecasting, etc. They utilize massive parallel
processing; for example, 5,800 processors and more than a trillion bytes of RAM.
3.3.1.6 Clean agent fire extinguishing systems are provided to limit the thermal and nonthermal damage
due to a fire originating within the room at an incipient stage.

3.3.2 Hot/Cold Aisle Containment and Hot Collar Systems

3.3.2.1 Hot/cold aisle containment (see Figures 2.5.2.11.A, B, and C), particularly at the ceiling, presents
challenges to fire protection in data processing centers. Among the concerns for this occupancy are:
• Shielding and obstruction of ceiling sprinklers
• Shielding and obstruction of smoke detection systems
• Failure of halocarbon or inert gas extinguishing agents to properly penetrate the equipment beneath
the containment
• Introduction of plastic combustibles into the room
3.3.2.2 FM4910 plastics limit fire spread, smoke damage, and damage from the corrosive byproducts of fire.
Currently, FM4910 plastics are limited to rigid sheet materials; there are no FM4910 flexible plastics at this
time.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 53

3.3.2.3 The use of flexible plastics for containment is not recommended partly because flexible plastics include
plasticizers, which create more corrosive smoke when burned. If flexible plastics are used for containment,
the thinnest material available should be used.
3.3.2.4 Releasing device assemblies (fusible links, thermal mechanical links and mechanisms) for removable
of curtains and aisle containment materials used with containment systems need to be listed by a National
Recognized Testing Laboratory (NRTL) (e.g., FM Approvals) in a fire protection application. At this time no
releasing device assemblies are listed since there is not a NRTL Standard. Further research and testing is
required to understand the capability of activating these releasing devices without impacting the response
time of the protection system to perform effectively. Usage of these devices increases the complexity to
provide proper protection compared to providing additional sprinklers or clean agent nozzles.
3.3.2.5 When the room has a halocarbon or inert gas (clean agent) fire extinguishing system that is activated
by a VEWFD detection system, take into consideration the location of the nozzles from which the clean agent
will be discharged; the nozzles should not be blocked from the containment system. Also take into
consideration the design concentration for the protection of the containment system volume independent of
the data processing equipment room in order for the proper concentration to be delivered in both areas.
3.3.2.6 Consider the type of air-handling unit (AHU) design, for continuous distribution of the halocarbon or
inert gas extinguishing agent to all areas of the containment aisles. The cooling air in a data processing
equipment room is typically circulated in a closed loop from the air-handling unit to below the raised floor
to the equipment, into the return air ducts, and back to the equipment. Some designs include single pass
airflow such that all cooling comes from the outside and exits the building without any recirculation. Also, some
designs include the options for anything between single pass to total recirculation, depending on conditions.
3.3.2.7 When evaluating the need for detection beneath a containment ceiling, keep in mind that standard-
response, spot-type smoke detectors under containment ceilings and within containment curtains may be
significantly impaired due to their reliance on air-flow velocity and positioning. An air-sampling, VEWFD
system is more advantageous.

3.3.3 Tape Cartridge Storage

An automated tape library is a hardware device that contains multiple tape drives for reading and writing
data, access ports for entering and removing tape cartridges and a robotic device for mounting and
dismounting the tape cartridges without human intervention. The tape cartridges are usually constructed of
a plastic material and can be numerous within the tape library. When constructed of combustible material
are a possible fuel source. The robotic devices are electrically powered and can be considered as an ignition
source. Hence, the recommendations for detection and suppression within the automated tape library
equipment.
The virtual tape library (VTL) combines traditional tape backup methodology with disk technology to create
backup and recovery features.
By backing up data to disks instead of tapes, VTL often increases performance of both backup and recovery
operations. In some cases, the data stored on the VTL’s disk array is exported to other media, such as
physical tapes.
The VTL disk storage is not designed to be removable. Since the disk storage is always connected to power
and data sources, it is exposed to potential impact from data center interruptions.

3.3.4 Mobile/Modular Data Center

Mobile/modular data centers allow for substantial economies of scale and have been designed for efficient
use of energy, including considerations regarding the external environment. Fabrication techniques can be
used to reduce manufacturing costs.
Modular data centers are designed for rapid deployment, and high-density computing to deliver data center
capacity at a lower cost than with traditional construction methods, and to significantly reduce construction
and equipment installation times.

3.3.5 Diagnostic Equipment

The recommendations in this data sheet are intended to supplement the recommendations in the applicable
data sheet for which the diagnostic equipment is installed (e.g., hospitals, clinics, and office buildings).

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 54 FM Global Property Loss Prevention Data Sheets

3.3.6 Quantum Computers

Quantum computers have not yet reached full commercial viability, however, there is a significant amount
of research and development in the hardware and software related to this technology. Quantum computers
are most likely to be located at research establishments, universities and the research campuses of large
tech organizations. Quantum computers are expensive (US$5-10 million), and outside of their encapsulation
(vacuum and cryogenic chamber) are highly susceptible to nonthermal damage. To operate, high vacuums
and very low temperatures are needed, to maintain stable operation of the quantum chip. Should multiple
quantum computers be connected to single support systems, for vacuum, refrigeration and power,
considerations should be given to the impact to multiple quantum computers. Along with the quantum
computer, large amounts of conventional computing power is needed to analyze and correct errors from the
data generated. This conventional computing power will likely be located in server rooms or data centers
away from the quantum computers.

3.4 Utilities

3.4.1 Electrical Power Distribution

3.4.1.1 Figures 3.4.1.1.a and 3.4.1.1.b show the typical electrical power distribution for a data center. This
drawing groups electrical equipment into different spaces (electrical space, IT space, mechanical space).
These spaces are typically located in different parts of the facility: The IT space is the data center equipment
room, and the electrical space is the substation and switchroom. Cooling systems are usually located in the
AHU or machinery room; however, there may also be cooling systems located within the data center.
Due to their large power demand, as well as the need for an electrical supply with good power quality, data
centers are typically supplied by medium-voltage, three-phase power from the utility.
IT equipment operates on single-phase, low-voltage power. The three-phase medium-voltage power is
stepped down to a low voltage by a facility-owned transformer to feed low-voltage switchgear.
The low-voltage supply from the transformer is typically a four-wire system with a grounded neutral. The
grounded neutral is important for electrical protection as well as power quality considerations.
Because of the importance of maintaining a secure power supply for the data center, utility power to IT
equipment is supplied through uninterruptible power supplies (UPS). These UPSs are fed from the low-voltage
switchboard and distribute filtered, uninterruptible power to the data center through UPS switchgear. See
Figure 3.4.1.1.c.
Typically, UPSs are of the static type, where utility power is used to charge batteries that take over when
there is a loss of power.
Because static UPSs have a limited power supply duration, most data centers will also have a standby diesel
generator that supplies essential power to the data center for IT equipment and some lighting and cooling.
This standby power may not be sufficient to run the full electrical load for auxiliary operations (e.g., offices,
conference rooms) in the data center.
Some data centers may use dynamic UPSs. These are driven by a diesel generator and have a longer power
supply duration. Depending on the capacity of the dynamic UPSs, it may not be necessary to have a separate
emergency diesel generator.
In addition to IT equipment, the low-voltage switchgear in the electrical space also supplies other equipment
such as the data center cooling and lighting systems. Cooling systems that have a high power demand may
be fed directly from the medium-voltage switchboard.
Within the IT space, typical arrangements for supplying the racks are shown in Figures 3.4.1.1.a and 3.4.1.1.b:
A. A power distribution unit (PDU) feeding a remote power panel (RPP). The PDU typically consists of a
main input circuit breaker, a transformer, panelboards, surge arrestors, output power cables, and metering
and control modules. The RPP is similar to the PDU but has no transformer; it has an input circuit breaker
and panelboards with metering and control modules that distribute power to the racks. The PDU and RPP
are equipment cabinets that sit on the raised floor in the data center.
B. A plug-in busduct. The busduct has a feed unit connecting the bus to the upstream switchboard with
plug in units directly feeding each rack. The busduct can be located overhead or under the raised floor.
Metering and control functions are provided in the feed unit. When power reaches the equipment racks,

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 55

a rack power distribution unit (rPDU) distributes the power to individual equipment. This is essentially a
power strip into which individual IT equipment is plugged.

U1 U2

Normally
Open

U1main ER1 ER2 X-Conn ER3 ER4 ER-E U2main

ATS ATS ATS ATS ATS

MAIN MAIN MAIN MAIN MAIN
SWITCHGEAR SWITCHGEAR SWITCHGEAR SWITCHGEAR SWITCHGEAR

UPS UPS UPS UPS UPS

Bypass Bypass Bypass Bypass Bypass

UPS w/ UPS w/ UPS w/ UPS w/ UPS w/

Mechanical

Mechanical

Mechanical
Mechanical
Mechanical

SWBD

SWBD

SWBD
SWBD
SWBD

STS STS STS STS STS

UPS UPS UPS UPS UPS

SWBD SWBD SWBD SWBD SWBD

STS

STS

STS STS
PDU PDU PDU PDU PDU PDU
PDU PDU MEC
CRA C/H PDU PDU CRA C/H
1-D 4-A
PDU PDU PDU PDU PDU PDU (Mechanical Electrical
Option 1:
Fed from
Option 1:
PDU Pair Option 2A:
Option 2B:
Option 3:
STS-PDU
Option 4:
STS-PDU
Option 1:
Fed from
Chase)
two Elec. PDU 1-D: ER1 PDU/PDUs w/ N:ER# N:ER# N:ER#
PDU/PDUs w/
Rms. PDU 4-A: ER 4 STS in MEC. A:ER-E A:ER# A:ER-E
STS in Elec. Rm.
Power Strip (ePDU)

Power Strip (ePDU)

Power Strip (ePDU)

Power Strip (ePDU)

Data Hall
Server

Server
Racks

Racks

Fig. 3.4.1.1.a. Electrical power distribution for a data center (Redundant Distribution)

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 56 FM Global Property Loss Prevention Data Sheets

U2
U1

Normally
Open

U1main ER1 ER2 X-Conn ER3 ER4 U2main

Swing Gen Gen1

SWING ATS*
A-SIDE B-SIDE
GEN A-SIDE BKR
MAINS
BKR B-SIDE
BKR*
Electrical Room 1

UPS Maintenance Bypass

UPS Maintenance Bypass

UPS Bypass

UPS Bypass
ATS ATS ATS ATS
U U U U
P P P P
S S S S
HVAC

HVAC

STS STS

UPS SWBD UPS SWBD

HVAC:
• Roof Top Unit (RTU)
or
• Computer Room Air Conditioner/
Handler(CRAC or CRAH)

HVAC

Power Strip (ePDU)

PDU PDU A1 PDU
Data Center Suite 1

PDU B1 Server Racks

A1 Power Strip (ePDU)
B1

Power Strip (ePDU)

PDU PDU A2 PDU
Server Racks
A2 Power Strip (ePDU)
PDU B2 B2

PDU PDU
A3 B3

PDU PDU
A4 B4
HVAC

PDU Pair:
PDUs are organized in pairs such that a loss of a single side will not affect power
continuity at the rack - dual corded

* The ATS function is typically accomplished using PLC control of the Main and
Gen1 circuit breakers. Upon loss of normal power the load will transfer to Gen1.
Should the load fail to transfer to Gen1 then the PLC will automatically shift the
load to the Swing Gen. The Swing Gen typically provides back-up for multiple
generators.

Fig. 3.4.1.1.b. Electrical power distribution for a data center (PDU Pairing)

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 57

UPS

UPSs
Batteries
UPSs can have different types of battery string disconnects.
• Single disconnect (older design)
• Individual disconnects for each string.
Single Disconnect
- Individual battery disconnects allow maintenance and
battery replacement to occur without having to take the
UPS offline.
UPS
Not shown here are the input and output filter capacitors. These
capacitors should be checked during the annual maintenance
performed on the UPS.

Batteries

Multiple Disconnect

Fig. 3.4.1.1.c. Uninterruptible power system for a data center)

3.4.1.2 Li-ion Battery Back-up Units in Data Processing Equipment Rooms

Data centers are moving towards battery back-up units (BBU) using Li-ion battery modules as in data
processing equipment rooms. Battery backup units (BBU’s) are installed in data processing server racks to
provide localized uninterruptible power to the data processing equipment in the event of a main utility power
failure and reduce peak power demand of the data center. BBUs are designed to be installed within a server
rack in place of a server. Typical installations will have BBUs located in 2-6 server slots within a rack (see
Figure 2.4.4.1). Each company has their own proprietary technology, arrangement, specification, battery
power, quantity and layout of the BBU’s within the racks. See Figure below for example of a rack layout
containing power shelves.
Introducing Li-ion BBU’s into data center presents ignition sources to the data processing equipment room
that did not previously exist. This additional ignition source has the potential to increase the frequency of fire
losses in this occupancy, and therefore calls for a tighter control of material flammability in the data hall,
e.g., cables, cold/hot aisle separation panels, and other plastics and combustible materials on the computer
servers and racks. In addition, fire intensity and severity compared to that typically expected in data
processing equipment rooms without distributed power systems, will be increased. With multiple BBU’s
installed in server racks there is the potential for continuous thermal runaway caused by overheating of
adjacent BBU’s. This has the potential to cause larger more damaging fires, with the added risk of reignition
following a fire event.
Halocarbon and inert gas (Clean Agent) protection systems are not recommended for BBU applications for
the following reasons:
A. Efficacy relative to the hazard. As of 2019, there is no evidence that gaseous protection is effective
in extinguishing or controlling a fire involving energy storage systems with Li-ion batteries. Halocarbon and
inert gas (clean agent) protection systems may inert or interrupt the chemical reaction of the fire, but only
for the duration of the hold time. The hold time is generally ten minutes, not long enough to fully extinguish
an Li-ion battery fire or to prevent thermal runaway from propagating to adjacent modules or racks.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 58 FM Global Property Loss Prevention Data Sheets

B. Cooling. FM Global research has shown that cooling the surroundings is a critical factor to protecting
the structure or surrounding occupancy because there is currently no way to extinguish an Li-ion battery
module fire with sprinklers. Gaseous protection systems do not provide cooling of the Li-ion batteries or the
surrounding occupancy.
C. Limited Discharge. FM Global research has shown that Li-ion battery fires can reignite hours after the
initial event is believed to be extinguished. As gaseous protection systems can only be discharged once,
the subsequent reignition would occur in an unprotected occupancy.
Battery back-up units consist of a number of individual lithium-Ion cells, cells are rated in Ampere hours (Ah)
and Voltage (V). To determine the kWh output per cell the following should be used:
Ah x V
1000 = kWh
Once the kWh per cell is known this should be multiplied by the number of cells in the module giving the
overall output per module.
The module output should then be multiplied by the number of modules per rack to determine the kWh per
rack.
The output of individual BBU’s should be available from the equipment operator and is usually reported as
kWh for the overall unit.

3.4.2 Electrical Protection for the Data Center

3.4.2.1 There are several layers of electrical protection for the data center. These are described below, starting
at the rack and working backward toward the utility supply:
A. The power supply for individual IT equipment is fitted with over-temperature, overload, and short-circuit
protection. This protection is primarily designed to protect the individual IT equipment from damage if
there is problem with the power supply.
B. Rack power distribution units (rPDUs) are similar to power strips used in office and residential buildings
and typically do not have any protection. Sometimes, over-temperature and overload protection is
provided at the power strip.
C. Remote power panels (RPPs) have overload and short-circuit protection for each of the feeders to
the rPDUs. These are provided at the branch circuit breakers and main circuit breaker of the RPP.
D. PDUs have overload and short-circuit protection for each of the feeders to the RPPs. Ground fault
protection may also be provided at this level. If there are transformers in the PDU, there will be over-
temperature and overload protection for the transformer. This protection is provided at the branch circuit
breakers and main circuit breaker of the PDU.
E. The UPS distribution switchboard has overload and short-circuit protection for each of the feeders to
the PDUs. Ground fault protection may also be provided at this level. In addition there is protection for the
battery charger, inverter, and rectifier.
F. The low-voltage switchboard has overload, short-circuit, and ground fault protection for every feeder.
This is provided at the main incoming LV breaker as well as at each of the branch circuit breakers.
G. The medium voltage switchboard has overload, short-circuit, and ground fault protection. Transformer
protection for the MV/LV transformer is also provided. Transformer protection is provided at the circuit
breakers for the utility and transformer feeders. Control and tripping power for these circuit breakers may
be present.This level of electrical protection means that when electrical faults occur within the data center
or within the electrical distribution system, protection will detect and remove the electrical fault by
de-energizing the equipment where the fault has occurred.
3.4.2.2 Although there is a relatively high level of electrical protection throughout a data center, there are
scenarios in which this electrical protection may not be able to detect an electrical fault and will therefore not
de-energize the faulty equipment and remove the ignition source. These scenarios include the following:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 59

A. Series arcing. Series arcing occurs when there is a break in the conductor or a loose connection that
results in a discontinuity in the circuit. If the discontinuity or break is not large enough, current will still
flow across the break as an arc. Series arcing is limited to less than the load current and as a result will
not be detected by over-current protection.
B. High-resistance parallel arcing. The other type of arcing is parallel arcing, where the insulation between
energized conductors or between a conductor and ground is compromised and current is allowed to flow
as an arc. The fault current that flows during this type of arcing is very high and short circuit protection
is designed to detect and remove this type of electrical fault. However, under some circumstances, where
the arc resistance is high, the fault current may not be large enough to activate short circuit protection.
C. Loose electrical connections. Loose electrical connections can lead to overheating. This overheating will
not be detected as an overload if the load current does not increase. Loose electrical connections are
also a source of series arcing. Series arcing cannot be detected by conventional electrical protection.
D. Circuit breaker failure. Circuit breakers are mechanical devices and can fail to operate. Circuit breakers
also have a limited fault-interrupting rating and may fail to properly interrupt a fault that exceeds their
rating. These types of faults may also weld the contacts of circuit breakers, preventing them from opening.
E. Incorrect or faulty grounding. Grounding is critical in ensuring the correct operation and detection of
electrical protection. Incorrect or faulty grounding can lead to malfunctioning electrical protection or faults
that cannot be detected by electrical protection.

3.4.3 Voltages Used in Various Countries

Sometimes equipment designed to be used in certain countries is used in data centers in countries that do
not use the same voltage. Most modern equipment will work within a wide range of voltages; however, some
older or specialized equipment may not be as tolerant of different voltages. In these cases, a transformer is
used to create the voltage needed by these equipment.
Table 3.4.3 shows the different medium and low voltage arrangements that are used in different countries.
As an example, equipment designed for use in Japan with a voltage rating of 100V would need a special
transformer to allow it to be used in other countries. These transformers are not off the shelf items and it
could take a long time to source a replacement.

Table 3.4.3. Medium and Low Voltages Used in Various Countries

Country Medium Voltage, kV Low Voltage
North America 4.16 600 V 60 Hz 3 wire + ground
12.47 600/347 V 60 Hz 4 wire + ground
13.2 480/277 V 60 Hz 4 wire + ground
13.8 480 V 60 Hz 3 wire + ground
34.5 208/120 V 60 Hz 4 wire + ground
415/240 V 60 Hz 4 wire + ground
South America 6 220/127 V 60 Hz 4 wire + ground
11 380/220 V 60 Hz 4 wire + ground
13.8 400/230 V 50 Hz 4 wire + ground
22
23
Europe 10 400/230 V 50 Hz 4 wire + ground
20 480/277 V 60 Hz 4 wire + ground
35
China 10 380/220 V 4 wire + ground
35
Japan 6.6 200 V 3 wire + ground
22 200/100 V 3 wire + ground
100 V 2 wire + ground
Australia 6.6 415/240 V 50 Hz 4 wire + ground
11
33

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 60 FM Global Property Loss Prevention Data Sheets

3.4.4 Power-Down of Data Processing Equipment and HVAC Systems

3.4.4.1 Electrical power is an ignition source in data centers. When power continues to be provided to
consumed combustibles, it has the capacity to re-ignite a fire, even if the flames are initially extinguished
by water-based or gaseous fire protection.
Automatic de-energizing of data processing equipment removes a possible re-ignition source, improves the
effectiveness of halocarbon or inert gas (clean agent) fire extinguishing systems, and minimizes damage
to exposed electronic circuits. This can be initiated by interfacing automatically with a smoke detection system
or a water flow switch for the sprinkler or water mist system.
Power-down of the HVAC system(s) warrants the following considerations:
• HVAC power-down upon smoke detection may prevent heat and/or smoke from being drawn into
data processing equipment.
• Allowing retention of the clean agent concentration when make-up air is introduced to the data
processing equipment room.
• HVAC power-down upon smoke detection may cause elevated ambient temperatures within the
data center. Sustained elevated temperatures may cause damage to the data processing equipment.
The possible damage may vary as a function of the exposure, data processing equipment design, and
materials of construction.
When coordinating isolation of power to data processing equipment and HVAC equipment, consider the
anticipated rate of rise of the data processing equipment room temperature if HVAC cooling is interrupted
without removing power from the data processing equipment cooled by those HVAC units. Provide cooling
for a sufficient time to prevent the room temperature from rising above a level that would result in damage of
data processing equipment or warranty issues (see Section 2.7.7). Coordinate the shutdown of HVAC air
handlers resulting from the performance goals of these power isolation guidelines with local code
requirements (e.g., duct-mounted smoke detection at HVAC air-handler inlet or outlets).
A single disconnect control integrated to de-energize and interlock both data processing equipment and HVAC
systems is preferred but is a condition of the previous considerations.
For areas/rooms protected by only a clean agent fire extinguishing system, initiation of an automatic or
automatic with time delay power-down of the data processing equipment sequence should occur at the alarm
for discharge of the halocarbon or inert gas (clean agent) fire extinguishing system as recommended in
Section 2.8.2. Power isolation of the HVAC will be dependent upon the system design for incoming air which
may dilute the concentration of extinguishing agent.
For areas/rooms protected by either automatic sprinkler systems or water mist systems, initiation of an
automatic power isolation of the data processing equipment sequence should occur from any type of smoke
detection or the water flow alarm for the sprinkler system or water mist system as recommended in Section
2.8.2.
For areas/rooms protected by a halocarbon or inert gas (clean agent) fire extinguishing system and with
sprinkler or water mist protection, initiation of an automatic or automatic with time delay power-down sequence
should occur at the alarm for discharge of the halocarbon or inert gas (clean agent) fire extinguishing system
as recommended in Section 2.8.2.
The purpose of a manual disconnect control is to preemptively initiate the de-energizing or “soft” power-down
sequence of data processing equipment and/or the HVAC system from the automatic power-down.

3.4.4.2 Manual Disconnect Controls

3.4.4.2.1 For manual disconnect controls:
A. Group by function and/or zone the disconnect control(s) for the de-energizing and interlock of data
processing equipment power and/or HVAC systems, respectively.
B. Identify the disconnect control(s) for the de-energizing and interlock of data processing equipment power
and/or HVAC systems, respectively.
C. Use a disconnect control with a tamper-proof design.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 61

D. Provide signal supervision at the fire alarm control panel of electrical interlocks and power-down devices
that de-energize data processing equipment.
E. Clearly identify circuit breakers as to the zone(s)/portion(s) of the data center they control.
3.4.4.2.2 Sprinklers and Water Mist Systems
The objective of automatic sprinkler systems and water mist systems in data centers is to control a fire; that
is, to limit fire propagation to a small area beyond the region of the ignition and initial fire, and to reduce
the heat release rate to a sufficiently low level that the number of sprinklers that activate is less than the design
area to maintain sufficient pressure in the water supply. If the electrical power is not interrupted as
recommended, reignition of a fire from the continued delivery of electrical power is eliminated by the cooling
effect of water. The power can be eventually interrupted in a controlled manner with coordination of final
manual fire extinguishment by the local fire service.
3.4.4.2.3 Halocarbon and Inert Gas (Clean Agent) Fire Extinguishing Systems
The objective of halocarbon or inert gas (clean agent) fire extinguishing systems in data centers is to limit
the extent and severity of damage to data processing equipment, and reduce the associated business
interruption to a much lower level than results from sprinkler protection alone. If a clean agent fire
extinguishing system is provided, sprinklers in the same space are not expected to activate because the
clean agent fire extinguishing system is activated by smoke detection that is much more sensitive than
sprinklers. Clean agent fire extinguishing systems are designed to maintain an adequate concentration of
agent in the protected space for only a limited period of time (typically 10 min.). This is a reflection of the
practical limitations in constructing rooms to be as airtight as possible, which industry experience has shown
to be exponentially more difficult with longer “hold times.”
Once the agent concentration is reduced to below the required level, if the ignition source has not been
removed by shutting off the power to the data processing equipment of fire origin, the fire will reignite any
combustibles. This concentration reduction occurs either by natural seepage of the extinguishing agent
through cracks in the building over a short time after initial agent release, or when the doors are opened to
admit emergency response team or fire service personnel. Therefore, power down must be accomplished
within this timeframe to prevent reignition. If a clean agent fire extinguishing system is the only fire protection
installed in the space (i.e., there are no sprinklers) and the energized data processing equipment is not
powered down, an uncontrolled fire will result, with fire propagation to the limit of combustibles.

3.4.5 Heating, Ventilation, and Air Conditioning (HVAC)

HVAC equipment is a frequent source of liquid leakage; locating it above critical equipment increases the
exposure to that equipment (this is not intended to apply to equipment mounted on the roof).

3.4.6 Uptime Institute Tier Classification

The Uptime Institute, Inc. is an independent company devoted to maximizing efficiency and uninterruptible
availability in data centers and information technology organizations. The Institute has developed the Tier
Classification System for rating the concurrent maintainability and fault tolerance of data center facilities (see
Table 3.4.6)

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 62 FM Global Property Loss Prevention Data Sheets

Table 3.4.6. Tier Requirements Summary

Tier I Tier II Tier III Tier IV
Active Capacity N N+1 N+1 N after any failure
Components to
Support IT Load
Distribution Paths 1 1 1 active and 1 2 simultaneously
alternate active
Concurrently No No Yes Yes
Maintainable
Fault Tolerancesingle No No No Yes
event)
Compartmentalization No No No Yes
Continuous Cooling No No No Yes
(*load density
dependent)

A Tier 1 basic data center has non-redundant capacity components and a single, non-redundant distribution
path servicing the computer equipment. The site is susceptible to distribution from both planned and
unplanned activities. The site infrastructure must be completely shut down to perform preventive maintenance
and repair work.
A Tier II data center has redundant capacity components and a single, non-redundant distribution path serving
the computer equipment. The site is susceptible to distribution from both planned and unplanned events.
Redundant capacity components can be removed from service on a planned basis without causing any of
the data processing equipment to be shut down.
A Tier III data center has redundant capacity components and multiple independent distribution paths servicing
the data processing equipment. Each and every capacity component and element in the distribution paths
can be removed from service on a planned basis without impacting any of the data processing equipment.
Planned site infrastructure maintenance can be performed by using the redundant capacity components and
distribution paths to work on the remaining equipment.
A Tier IV data center has multiple, independent, physically isolated systems that each has redundant capacity
components and data, independent, diverse, active distribution paths simultaneously servicing the data
processing equipment. A single failure of any capacity system, capacity component, or distribution element
will not impact the data processing equipment. The site infrastructure maintenance can be performed by
using the redundant capacity components and distribution paths to safely work on the remaining equipment.
For additional details, see the Uptime Institute’s, LLC “Data Center Site Infrastructure Tier Standard:
Topology”, Uptime Institute Professional Services, LLC, 2012.

3.5 Loss History

3.5.1 NFPA
A study by NFPA in 2004 concluded that properties wholly dedicated to computer or telecommunications
activities are a comparatively small part of the United States fire problem. In this study, electronic equipment
areas included computer areas, data processing centers, control centers, radar rooms, telephone equipment
rooms, and telephone booths. The main conclusions of this survey included the following:
• A large number of fires in electronic equipment rooms do not begin with the electronic equipment
or even with any equipment.
• The leading cause of fires in electronic equipment areas involves electrical distribution equipment
(e.g., wiring, cables, cord, plugs, outlets, overcurrent protection devices), but not electronic
equipment.
• In most cases, fire damage is limited to the object of origin.
The results of this study are consistent with FM Global loss experience.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 63

4.0 REFERENCES

4.1 FM Global
Data Sheet 1-2, Earthquakes
Data Sheet 1-3, High-Rise Buildings
Data Sheet 1-6, Cooling Towers
Data Sheet 1-8, Antenna Tower and Signs
Data Sheet 1-12, Ceiling and Concealed Spaces
Data Sheet 1-20, Protection Against Exterior Fire Exposure
Data Sheet 1-28, Wind Design
Data Sheet 9-1, Supervision of Property
Data Sheet 9-13, Evaluation of Flood Exposure
Data Sheet 1-24, Protection Against Liquid Damage
Data Sheet 1-40, Flood
Data Sheet 1-45, Air Conditioning and Ventilating Systems
Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers
Data Sheet 2-8, Earthquake Protection for Water-Based Fire Protection Systems
Data Sheet 2-81, Fire Protection System Inspection, Testing and Maintenance and other Fire Loss Prevention
Inspections
Data Sheet 3-0R, Hydraulics of Fire Protection Systems
Data Sheet 3-7, Fire Protection Pumps
Data Sheet 3-26, Fire Protection Water Demand for Nonstorage Sprinklered Properties
Data Sheet 4-2, Water Mist Systems
Data Sheet 4-9, Halocarbon or Inert Gas (Clean Agent) Fire Extinguishing Systems
Data Sheet 4-11, Carbon Dioxide Extinguishing Systems
Data Sheet 5-4, Transformers
Data Sheet 5-11, Lightning and Surge Protection for Electrical Systems
Data Sheet 5-14, Telecommunications
Data Sheet 5-19, Switchgear and Circuit Breakers
Data Sheet 5-20, Electrical Testing
Data Sheet 5-23, Design and Protection for Emergency and Standby Power Systems
Data Sheet 5-28, DC Battery Systems
Data Sheet 5-28, DC Battery Systems
Data Sheet 5-31, Cables and Bus Bars
Data Sheet 5-40, Fire Alarm Systems
Data Sheet 5-48, Automatic Fire Detection
Data Sheet 7-13, Mechanical Refrigeration
Data Sheet 9-0, Asset Integrity
Data Sheet 9-1, Supervision of Property
Data Sheet 9-16, Burglary and Theft
Data Sheet 9-17, Protection Against Arson and Other Incendiary Fires
Data Sheet 10-1, Pre-Incident Planning
Data Sheet 10-5, Disaster Recovery Planning
Data Sheet 10-8, Operators
Data Sheet 13-24, Fans and Blowers
Data Sheet 13-26, Internal Combustion Engines
Thumuluru, S., Ditch, B., Chatterjee, P. and Chaos, M. Experimental Data for Model Validation of Smoke
Transport in Data Centers. Research Technical Report. FM Global, September 2014.
Xin, Y. and M. M. Khan. “Flammability of combustible materials in reduced oxygen environment.” Fire Safety
Journal 42 (2007) pp. 536-547.

4.1.1 FM Approvals
Class Number 3972, Test Standard for Cable Fire Propagation
Class Number 4882, Class 1 Interior Wall and Ceiling Materials or Systems for Smoke Sensitive Occupancies
Class Number 4884, Panels Used in Data Processing Center Hot and Cold Aisle Containment Systems
Class Number 4910, Cleanroom Materials Flammability Test Protocol
Class Number 4924, Approval Standard for Pipe Insulation

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 64 FM Global Property Loss Prevention Data Sheets

Class Number 4955, Approval Standard for Flammability of Absorbent Battery Acid Spill Containment Pillows
Class Number 5420, Approval Standard for Carbon Dioxide Extinguishing Systems
Class Number 5600, Approval Standard for Clean Agent Fire Extinguishing Systems
Class Number 5560, Approval Standard for Water Mist Systems

4.2 Other Standards

American Society of Testing Materials (ASTM). Standard Method of Surface Burning Characteristics of
Building Materials. ASTM E84. 2010
British Standard Institute (BSI). Fire protection for electronic equipment installations - Code of practice. BS
6266:2011.
British Standard Institute (BSI); European Norm. Communication cables. Specifications for test methods.
Environmental test methods. A horizontal integrated fire test method. BS-EN-50289-4-11, 2002.
Deutsches Institut für Normung e.V. (DIN). Testing of combustible materials; response to ignition by a small
flame. DIN 53438, 1984
Deutsches Institut für Normung e.V. (DIN). Fire Behaviour of Building Materials and Building Components.
DIN 4102, 2009.
Institute of Electrical and Electronics Engineers (IEEE). Recommended Practice for Powering and Grounding
Sensitive Electronic Equipment. IEEE Std 1100 1992, 1992.
Institute of Electrical and Electronics Engineers (IEEE) / American Society of Heating, Refrigerating, and
Air-Conditioning Engineers (ASHRAE). Guide for Ventilation and Thermal Management of Batteries for
Stationary Applications. IEEE 1635, 2012, ASHRAE Guideline 21, 2012.
National Fire Protection Association (NFPA). National Electrical Code. NFPA 70, 2011, Article 645.
National Fire Protection Association (NFPA). Protection of Information Technology Equipment. NFPA 75,
2013.
National Fire Protection Association (NFPA). Fire Protection of Telecommunications Facilities. NFPA 76, 2012.
National Fire Protection Association (NFPA). Special Analysis Package Computer Equipment and Computer
Areas. Fire Analysis and Research Division, NFPA. 2001.
National Fire Protection Association (NFPA). Standard Method of Test of Surface Burning Characteristics
of Building Materials. NFPA 255, (Withdrawn 2009).
National Fire Protection Association (NFPA). Standard Method of Test for Flame Travel & Smoke of Wires
and Cables for use in Air - Handling Spaces. NFPA 262, 2011.
National Fire Protection Association (NFPA). Clean Agent Fire Extinguishing Systems. NFPA 2001, 2012.
Schneider Electric. Electrical Distribution Equipment in Data Center Environments. White Paper 61, Revision
1. Pearl Hu.
Turner, W. P., et. al. Tier Classifications Define Site Infrastructure Performance. Uptime Institute. 2008.
Underwriters Laboratories (UL). Tests for Flammability of Plastic Materials for Parts in Devices and
Applications. UL 94, 2010.
Underwriters Laboratories (UL). Test for Surface Burning Characteristics of Building Materials. UL 723, 2010.
Underwriters Laboratories (UL). Test Performance of Air Filter Units. UL 900, 2007.
Underwriters Laboratories (UL). UL Standard for Safety for Flame-Propagation and Smoke-Density Values
for Electrical and Optical-Fiber Cables used in Spaces Transporting Environmental Air. UL 910 (Withdrawn
2001).
Underwriters Laboratories (UL). Test Methods for Determining the Combustibility of Characteristics of Plastics
Used in Semi-Conductor Tool Construction. UL 2360, 2004.
Underwriters Laboratories (UL). Information Technology Equipment - Safety - Part 1: General Requirements.
UL 60950-1, 2007.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 65

Underwriters Laboratories (UL). Information Technology Equipment - Safety - Part 21: Remote Power
Feeding. UL 60950-21, 2003.

APPENDIX A GLOSSARY OF TERMS

Automated tape library (ATL): An enclosed storage and retrieval system that moves recorded electronic
data (e.g., cassettes) between storage and server equipment.
Air-aspirating detection: See “Very early warning fire detection (VEWFD).”
Availability: The degree to which a system, subsystem or equipment is in a operable state when it is
requested for use at any random time.
Battery Back-up Unit (BBU): Batteries housed inside a metal enclosure with a cross-sectional area of
approximately 4 sq. in (25 sq. cm). The individual battery unit is typically the length as the server. The module
is used for DC power backup and typically hot-swappable (i.e., it can be replaced without interruption to the
power circuit) in the server rack. The battery module may or may not contain a Battery Management Systems
(BMS).
Business continuity: A strategic approach to business as a whole, involving the development of a response
to safeguard the entire business by managing the impact of a disruption to achieve the company’s business
objectives for survival, regardless of the cause of the disruption. By implication, the development of the BCP
requires a much deeper understanding of the business, the criteria for business survival, the continuity
strategies available, and the resources necessary to implement the continuity response.
Building automation system: A centralized building automatic control system, usually controlling at least
the HVAC but that may also control lighting, security, safety, electric power, fire alarm, or any other building
system. Also known as a building management system (BMS).
Cold aisle: The aisle in front of the airflow intakes on the server racks where HVAC cooling airflow is
controlled.
Co-location: Rental to third parties of disk space, provision of web-hosting services on a server, or segmented
areas with individual tenants that control their own equipment.
Cloud computing: A model for enabling convenient, on-demand network access to a shared pool of
configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be
rapidly provisioned and released with minimal management effort or service provider interaction.
Computer room air conditioner (CRAC): An air handler that uses refrigerant and an internal compressor
dedicated to providing cooling air to the data processing equipment space. Cooling the air in the data
processing equipment room is accomplished by airflow over evaporation cooling coils where the refrigerant
is being directly expanded.
Computer room air handler (CRAH): An air handler dedicated to providing cooling air to the data processing
equipment space that uses chilled water cooling coils within the unit. Central cooling equipment (e.g., chiller)
is located in separate mechanical rooms.
Data center: A facility used to house data processing equipment and associated components, such as
telecommunications and storage systems. It generally includes redundant or backup power supplies,
redundant data communications connections, environmental controls (e.g., HVAC, fire suppression) and
security devices.
Data processing equipment room: A room mostly occupied with data processing equipment such as
servers, tape cartridge storage, printers, etc.
Disaster recovery: Activities necessary to respond to an incident at a location to restore normal operations
after a major disaster or specific scenario. DRPs are therefore written to establish the necessary actions
to take during and immediately after an anticipated event to expedite the resumption of normal operations.
Disconnect control: A device that controls the interface of the disconnecting means of power by a pathway,
relay, or equivalent method.
Double-interlock preaction system: A sprinkler system that is located downstream of a preaction valve
and is equipped with closed-type sprinklers. The preaction valve is arranged to open only after the actuation

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 66 FM Global Property Loss Prevention Data Sheets

of both a sprinkler and a detection system that is supervising the area being protected by the preaction
sprinkler system. Most double-interlock sprinkler systems have either an electric or a pneumatic means of
accomplishing these two activating conditions.
Emergency Power Off (EPO): See Manual Disconnect Control.
High-rise building: Any building with an occupied floor located more than 75 ft (23 m) above the lowest
level of fire service vehicle access with the exception of:
- Airport traffic control towers
- Open parking garages
- Amusement park structures
- Bleachers
- Grandstands
- Stadiums
- Special industrial buildings (ex. BLRB)
- Buildings with high hazard occupancies
Hot aisle: The aisle at the rear of the server racks into which air is directed after being heated by passing
through the data processing equipment for return to the HVAC equipment.
Hot/cold aisle containment: Physical barriers provided in the immediate vicinity of air-cooled server racks
that separate hot air exhausted from the data processing equipment from the cooler supply air into the
equipment racks. Containment is typically provided above and at both ends of a hot or cold aisle, in whole
or in part.
Hot air collar: An assembly used to duct heated exhaust air from an enclosure(s), cabinet(s,) or rack(s) of
the data processing equipment to the return air path of the HVAC system.
Input/output (I/O) room: The room where the electronic hardware is wired to interface from the control room
with the field/process devices. Discrete I/O devices have switches for inputs and relay outputs (e.g., operate
solenoid valves or pump motors). Analog I/O devices have process variable inputs, and variable controller
outputs.
Intelligent high-sensitivity spot detection: See “Very early warning fire detection (VEWFD).”
Listed: Listed by a reputable testing laboratory according to a widely recognized testing standard adopted
by model building codes.
Manual disconnect control: A means to preemptively initiate the de-energizing or “soft” power-down
sequence of data processing equipment and/or the HVAC system.
Mobile/modular data center: An enclosed construction unit or prefabricated container (e.g., ISO shipping
container) containing data processing equipment (e.g., servers, storage, networking, software management)
and/or supporting utility systems (e.g. power, power conditioning, HVAC) intended to be configured on a
modular basis either as a standalone unit or several units combined in an array to provide data center
functions.
N+1: Need plus one, a redundancy concept where operational capacity is met by one or more components
or systems, plus one additional component or system adequate to enable continued operations in the event
of a failure of one component or system in the base configuration.
Network Control room: A room serving as an operations center where a facility, service, or equipment can
be remotely monitored by electronic equipment and controlled by personnel. The network control room is
used in network, command and control, and other control application operations.
Network/fiber optic room: A space that supports cabling to areas outside the data processing equipment
room. The network/fiber room is normally located outside the data processing equipment room but, if
necessary, can be combined with a main distribution area, intermediate distribution area or horizontal
distribution area. The network/fiber room may also be referenced as the telecommunications room.
Non-interlock preaction system: A sprinkler system that is located downstream of a preaction valve and
is equipped with closed-type sprinklers. The preaction valve is arranged to open upon either the operation of
a sprinkler or the actuation of a detection system that is supervising the area being protected by the preaction
sprinkler system.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 67

Nonpropagating or Group 1 cable:

1. Cable with a fire propagation index (FPI) of less than 10 when tested in the FM Global fire propagation
apparatus.
2. Cable that, when tested in accordance with the FM 3972 Vertical Tray Test, does not have flame spread
more than 5 ft (1.5 m) beyond the 60 kW fire exposure.
3. Cable that has passed UL 910 or NFPA 262 tests.
Plenum-rated cable: Considered non-fire propagating and equivalent to FM Approved Group 1 cable.
Preaction sprinkler system: A sprinkler system that is located downstream of a preaction valve and is
equipped with closed-type sprinklers (i.e., sprinklers equipped with a thermal sensing element and an orifice
cap).
Preaction valve: An automatic water control valve, typically installed on a sprinkler system riser, specifically
designed to hold back water from passing through it until certain conditions have been met, such as activation
of a detection system supervising the area protected by the preaction sprinkler system or by pressure drop
downstream of the valve. It is connected upstream of a preaction sprinkler system.
Process control room: A cutoff and/or isolated room in which personnel are available 24/7 to operate a
process from a central or remote location. The process control room is typically integrated with an input/output
room and/or cable spreading room to control the function of equipment. Process control is extensively used
in industry and commonly enables mass production of continuous processes such as, paper, pharmaceuticals,
chemicals, and electric power as well as other industrial processes, such as supervisory control and data
acquisition (SCADA) systems. Process control rooms/technical spaces may be unattended and operated
remotely.
Propagating cable:
1. Cable with a fire propagation index (FPI) of more than 10 when tested in the FM Global fire propagation
apparatus.
2. Cable that, when tested in accordance with the FM 3972 Vertical Tray Test, has a flame spread greater
than 5 ft (1.5 m) beyond the 60 kW fire exposure.
3. Cable that has not been tested or has not passed UL 910 or NFPA 262 tests.
Proportional-integral-derivative (PID) controller: A control loop feedback mechanism controller commonly
used in industrial control systems. A PID controller continuously calculates an error value as the difference
between a desired setpoint and a measured process variable and applies a correction based on proportional,
integral, and derivative terms, (sometimes denoted P, I, and D respectively) which give their name to the
controller type.
Quantum Computer: A quantum computer is a machine that uses the properties of quantum physics to
store data and perform computations. The basic unit of memory is a quantum bit or qubit. Qubits are made
using physical systems, such as the spin it an electron or the orientation of a photon. Qubits can represent
numerous combinations of binary bits (1 and 0) simultaneously at the same time for potential outcomes.
Raceway: An enclosed channel of metal or nonmetallic materials designed for holding wires, cables or bus
bars.
Rack: Device for holding data center equipment, most commonly used to hold multiple servers. Also called
a cabinet.
Routing assembly: A single channel or connected multiple channels, as well as associated fittings, forming
a structure system that is used to support, route, and protect wires and cables.
Server: Data processing equipment that serves information to computers that connect to it. When users
connect to a server, they can access programs, files, and other information from the server. Common servers
are web servers, mail servers, and LAN servers.
Server farm: A collection of computer servers usually maintained by an enterprise to accomplish server needs
far beyond the capability of one machine. Server farms often have backup servers that can take over the
function of primary servers in the event of a primary server failure. Server farms are typically co-located with

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 68 FM Global Property Loss Prevention Data Sheets

the network switches and/or routers that enable communication between the different parts of the cluster
and the users of the cluster. The computers, routers, power supplies, and related electronics are typically
mounted on racks in a server room or data center.
Shelter-in-place: A building space designed and constructed to provide protection to occupants in a natural
or other disaster. The space may be structurally reinforced to resist the highest forces anticipated (e.g. wind,
impact, blast pressure, heat, etc.) and will provide breathable air for the expected duration of the emergency.
Single-interlock preaction system: A sprinkler system that is located downstream of a preaction valve and
is equipped with closed-type sprinklers. The preaction valve is arranged to open upon the actuation of a
detection system that is supervising the area being protected by the preaction sprinkler system.
Soft power-down: A disconnect control that triggers a sequence of data processing equipment commands
followed by de-energizing such that an orderly power-down is necessary to minimize data processing
equipment damage.
Tape library: In data storage, a tape library is a collection of magnetic tape cartridges and tape drives. An
automated tape library is a hardware device that contains multiple tape drives for reading and writing data,
access ports for entering and removing tapes and a robotic device for mounting and dismounting the tape
cartridges without human intervention.
Thermal runaway: Rapid heating of data processing equipment above critical operating temperatures, which
may cause short-term data processing equipment damage due to loss of cooling to the data processing
equipment space. Possible causes include loss of power to portions of or the entire facility, loss of power
to critical HVAC cooling components, and failure of individual HVAC components.
Unoccupiable enclosure or space: An enclosure or space that has dimensions and physical characteristics
such that it cannot be entered by a person.
Valve-regulated lead acid batteries (VRLA): Batteries designed to minimize gas emissions and eliminate
electrolyte maintenance by recombination of internally generated oxygen and hydrogen to conserve water.
A resealable valve is intended to vent gases not recombined, hence the term ″valve-regulated.” The electrolyte
in a VRLA cell is ″immobilized″ by the use of a highly porous fibrous mat between the plates or by the use
of a gelling agent to thicken the electrolyte.
Very early warning fire detection (VEWFD): These detectors maybe photo-electric spot-type or air-sampling
type detection systems. Spot detectors using xenon or laser light detection chambers can be considered
VEWFD detectors. VEWFD detectors are an order of magnitude more sensitive than conventional smoke
detectors. These detectors can be set to alert at smoke obscuration levels below 0.02 percent per foot (0.06
percent per meter) and an alarm condition at a smoke obscuration level below 1.0 percent per foot (3.1
percent per meter). Conventional smoke detectors alarm at 1 to 3 percent per foot (3.3 to 9.8 percent per
meter).
Zone: A distinct area, created by a physical barrier or division of open space, from the total area of a data
processing equipment room that is segmented into dedicated power and/or HVAC systems for the data
processing equipment.

APPENDIX B DOCUMENT REVISION HISTORY

The purpose of this appendix is to capture the changes that were made to this document each time it was
published. Please note that section numbers refer specifically to those in the version published on the date
shown (i.e., the section numbers are not always the same from version to version).
July 2023. Interim revision. Made editorial change to Table D-2 of Class C design concentration for
FK-5-1-12. Revised the minimum design concentration percentage to include the proper safety factor based
upon the Class A minimum extinguishment concentration.
January 2023. Interim revision. The following changes were made:
A. Updated recommendations in Section 2.4.4 to allow equipment using Li-ion batteries in distributed power
systems of data processing equipment to be protected with automatic water mist systems.
B. Made editorial updates to figures in Section 2.8.1, Electrical Distribution System and Section 3.4.1,
Electrical Power Distribution.
July 2022. Interim revision. The following significant changes were made:

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 69

A. Added recommendations for the protection of equipment using Li-ion batteries in the following:
1. Battery back-up units for distributed power systems of data processing equipment
2. Uninterruptable power supplies (UPS) (refer to Data Sheet 5-28, DC Power Systems)
3. Energy storage systems (reference to Data Sheet 5-33, Electrical Energy Storage Systems)
B. Modified guidance in Section 2.2, Construction and Location:
1. For multi-story data centers to be in accordance with specific sections of Data Sheet 1-3, High Rise
Buildings
2. To address leakage of liquids (Section 2.2.1.6) in accordance with Data Sheet 1-24, Protection
Against Liquid Damage
3. To provide preventing unauthorized access to a data center in accordance with Data Sheet 9-1,
Supervision of Property
C. Added recommendations to address the impact high velocity and horizontal airflow for the cooling of
data processing equipment has on the actuation and operation of sprinklers, water mist system nozzles,
and smoke detection (Section 2.4.3).
D. Updated guidance on the proper application of wet, single, and double interlock sprinkler and water
mist system configurations (Sections 2.4.7.1 and 2.4.7.2, respectively).
E. Updated recommendation and support guidance for oxygen reduction systems (Sections 2.4.1.7 and
3.2.1B) to conform with Data Sheet 4-13, Oxygen Reduction Systems.
F. Updated recommendations in Section 2.4.7.3.7 for the proper placement of FM Approved clean agent
fire extinguishing system discharge nozzles based on the listing to provide sound pressure level values
to hard disk drives that are susceptible to damage.
G. Updated guidance in Section 2.5.2, Hot/Cold Containment and Hot Collar Systems, to address inclusion
of FM Approved panels to the FM Approval Class 4884 Standard.
H. Added general guidance for “Quantum” computers in equipment and processes (Sections 2.5.1 and
3.3.1, respectively).
I. Added guidance for B&M equipment with the specialized recommendations for their application in data
centers and related facilities (Section 2.8, Utilities and Support Systems).
J. Updated recommendations for automatic power isolation in Section 2.8.2, Power Isolation of Data
Processing Equipment and HVAC Systems.
October 2021. Interim revision. Removed the recommendation on battery design, installation, inspection,
testing, and maintenance in this document. Replaced recommendations with reference to Data Sheet 5-28,
DC Battery Systems.
July 2020. Interim revision. Added equipment contingency planning and service interruption planning
guidance.
April 2020. Interim Revision. Clarifications were made in the following section:
1. A new general recommendation (Section 2.4.5) for local alarms to be annunciated at a constantly
attended location to be consistent with recommendations to allow for implementation of a Power Isolation
Plan.
October 2019. Interim Revision. The following changes were made:
A. Transferred Recommendations associated with process control rooms to OS/DS 7-110, Industrial
Control Systems.
January 2018. Interim revision. The folowing changes were made:
A. Added alternative method to anchoring of equipment for securement to earthquake.
April 2017. The following changes were made:
1. Revised the scope of this data sheet to identify when recommendations apply to telecommunication
facilities using Voice over Internet Protocol (VoIP) equipment and other related occupancies that have data
processing equipment rooms/halls.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 70 FM Global Property Loss Prevention Data Sheets

2. Added new recommendations to Section 2.2.1, General, for the proper location of HVAC equipment
in data processing equipment rooms.
3. Revised recommendations in Section 2.2.10, Earthquake, to align with the recommendations in Data
Sheet 1-2, Earthquakes.
4. Revised recommendations in Section 2.2.12, Flood/Storm Water Runoff, to align with the
recommendations in Data Sheet 1-40, Flood.
5. Revised the recommendation in Section 2.3, Occupancy, as follows:
a. Removed the allowance of two pallet loads of in-process storage in the data processing equipment
room based on the 2014 Engineering Support Project.
b. Added recommendation for storage to be in accordance with Data Sheet 8-9, Storage of Class 1,2,3,4
and Plastic Commodities.
6. Added recommendation in Section 2.4.5.7 for the use of portable smoke detection.
7. Revised recommendations in Section 2.4.6.1, Automatic Sprinklers, to include the following based on
the 2014 Engineering Support Project:
a. Removed recommendation for double-interlocked sprinklers.
b. Added recommendation for minimum pressure of sprinklers protecting elevated hazards.
8. Revised recommendations in Section 2.4.6.2, Water Mist Systems, based on the 2014 Risk Service
Project.
9. Added new recommendations to Section 2.4.6.3, Clean Agent Fire Extinguishing Systems, to address
the impact of noise (from discharge) on hard drives.
10. Revised the recommendation in Section 2.5.1.1, Equipment, on blanking plate materials of
construction.
11. Added new recommendation to Section 2.5.2.2 on materials that can be used for solid ceilings in
hot/cold aisle containment systems.
12. Revised the recommendations in Section 2.5.2.4, Sprinkler Protection for Hot/Cold Aisle Protection,
based on the 2014 Engineering Support Project.
13. Added Section 2.7.2 Power Isolation Plan.
14. Revised the recommendations in Section 2.7.5, Security, to align with Data Sheet 9-1, Supervision
of Property.
15. Added Section 2.7.7 Loss of Cooling Emergency Response Plan.
16. Revised Section 2.8.2, Power-Down of Data Processing Equipment and HVAC Systems. Changed
terminology from “power-down” to “power isolation.”
17. Added new recommendations to Section 2.8.5, Heating, Ventilation, and Air Conditioning Systems,
to address loss of cooling.
18. Added information to Section 3.1.3, Cables, to support the recommendation of not using power cables
with chlorinated polyethylene or polyvinyl chloride (PVC) sheathing or insulation.
19. Added information to Section 3.2.4.10, Portable Detection, to support the recommendation for the
usage of portable smoke detection.
20. Added new information to Section 3.2.5.3.7 regarding clean agent fire extinguishing systems to address
the impact of noise (from discharge) on hard drives.
21. Revised Section 3.4.1, Electrical Power Distribution, to provide more information on the types of power
supplies used in data centers.
22. Added Section 3.4.2, Electrical Protection for the Data Center, to provide more information on the
types of passive protection used for power supplies in data centers.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 71

23. Revised Section 3.4.4, Power-Down of Data Processing Equipment and HVAC Systems. Changed
terminology from “power-down” to “power isolation.”
24. Added the following terms to Appendix A, Glossary of Terms:
• Availability
• Building automation system
• Computer room air conditioner (CRAC)
• Computer Room air handler (CRAH)
• Listed
• Network/fiber optic room
• Proportionalintegralderivate (PID) controller
• Thermal runaway
25. Made editorial changes throughout the data sheet to clarify the intent of the recommendations.
July 2012. This data sheet has been completely rewritten. Major changes include the following:
1. Changed the title from Electronic Data Processing Systems to Data Centers and Related Facilities.
2. Added hot/cold aisle containment systems and protection recommendations.
3. Added the recommendation for the protection of foam insulation beneath raised floors in the data
processing equipment room.
4. Added guidance on using clean agent fire extinguishing systems and water mist systems.
5. Added protection recommendations for modular data centers.6.
Added protection recommendations for process control rooms, control rooms, and diagnostic equipment.
Recommendations in the specific sections for process control rooms, control rooms, and diagnostic
equipment when identified will supersede those for data centers.
7. Added recommendations for redundancy of certain critical utility systems: heating, ventilation and air
conditioning (HVAC) systems, chillers, and ventilation.
8. Updated the section on automatic power-down to include powering down and de-energizing data
processing equipment and HVAC systems.
9. Deleted the recommendation for automatic smoke control and removal systems.
May 2005. The revisions are based on a change in Data Sheet 5-31, Cables and Bus Bars. The change
combines FM Approved Group 2 and Group 3 cable along with cables that have not been tested by FM Global
and considers these as cables that can ‘‘propagate’’ fire. ‘‘Nonpropagating’’ cable does not require protection.
Nonpropagating cable is either (a) FM Approved Group 1, (b) UL-910 plenum rated or (c) cable with a
maximum flame spread distance of 5 ft (1.5 m) when tested in accordance with NFPA 262, Standard Method
of Test for Flame Travel and Smoke of Wires and Cables for use in Air Handling Spaces.
January 2005. Reference to the future use of Halon 1301 and 1211 systems for protection of computer and
computer related equipment has been replaced with a recommendation for the use of clean agent systems
installed in accordance with Data Sheet 4-9, Clean Agent Fire Extinguishing Systems.
September 2004. Recommendation 2.4.2.1.2 was modified to allow the use of light hazard water mist
systems FM Approved for open area protection.
September 2002. Recommendation for protection of subfloor areas of the computer room has been revised
to include the use of FM Approved Clean Agent fire extinguishing systems and water mist systems.
January 2001. The document has been reorganized to provide a consistent format.
September 2000. The document has been reorganized to provide a consistent format.
May 1999. The recommendation for grounding of computer systems was revised. Also, guidance for fire
protection of Group 2 cables that are randomly laid (unbundled across the floor) was modified.
June 1993. Data Sheet 5-32 has been completely rewritten.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 72 FM Global Property Loss Prevention Data Sheets

APPENDIX C PERFORMANCE TEST PROCEDURES FOR VEWFD SYSTEMS

Performance tests for VEWFD systems are intended to simulate the small amounts of smoke that would
be created in the early stages of a fire in a data processing equipment room. If an actual fire were to produce
the amounts of smoke produced by these tests, data center companies would want to be alerted by the fire
alarm system. The tests represent a good balance between the desire to use smoke sources that are
representative of the types of fires that have occurred in data processing equipment rooms and the desire
to minimize the introduction of smoke that can cause damage to operating data processing equipment in the
area/room.

C1. Objectives
Performance tests are intended to meet the general objectives listed below:
A. The tests are intended to be repeatable. A consistent quantity, temperature, and color of smoke are
produced each time the test is performed.
B. The test equipment can be quickly set up in actual data center facilities.
C. Testing is intended to prevent or minimize the potential for smoke damage to data processing equipment
in the room (little or no corrosive products of combustion should be produced).

C2. Heated Wire Test

This test uses an electrically overloaded PVC-coated wire to simulate the early stages of a fire. Although a
PVC wire is used, hydrogen chloride vapor is unlikely to be produced in quantities significant enough to be
of concern, due to the relatively low temperatures reached. If the current is applied for a longer time, or if the
wire sample is shorter than stated, small quantities of hydrogen chloride can be generated. In either event,
a clearly perceptible odor that should dissipate in a short time is produced by the test. Table C2 describes
two heated wire tests.

Table C-2. Heated-Wire Test Parameters

Modified BS 6266 Test:
Parameter 1 m Wires in Parallel North American Wire Test
Wire Specs Wire is very flexible due to stranded A single strand of 22 AWG copper
construction and highly plasticized wire, insulated with PVC to a radial
insulation. thickness of 1.1 mm (0.041 in.). This
wire is stiffer than the BSI wire due to
the single-strand construction and the
minimally plasticized PVC insulation.
Smoke Characterization More visible smoke than the 2 m test More visible smoke than the BSI wire
or the single wire 1 m test but still tests but still very light. A minor
very light smoke. Due to the higher amount of HCI is produced but for a
temperature in the wires, a small shorter duration than the BSI wires
amount of HCI vapor will be tests.
produced.
Test Period 60 seconds 30 seconds
Electrical Load Constant voltage -6.0 volts dc, current Constant current of 28 amperes.
varies from 0 to 30 amperes during Voltage varies from 0 to 18 volts dc
the test due to changing resistance in during test due to changing resistance
the wire. in the wire.
Pass/Fail Criteria ″Alert″ or ″pre-alarm″ signal within 120 seconds of the end of the period.

A. Test Apparatus
The test apparatus consists of the following:
1. Wire. Table D.1 lists options for wire selection and test parameters for the users to select. Test wire
should be cut cleanly to the length specified in Table C-2.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 73

2. Wire Mounting. The wire should be arranged by placing it on a noncombustible, nonconductive board,
or suspending it on a noncombustible, nonconductive support. The wire should be arranged so that there
are no kinks or crossovers where localized higher temperature heating can occur.
3. Power Supply and Leads. A regulated dc power supply should be capable of supplying a current of 0
to 30 amperes at 0 to 18 volts dc (i.e., Kenwood Model XL6524E-D). The lead wires between the power
supply and the test wire (s) should be 10AWG, 3.25 m (10.66 ft) long to avoid unacceptable voltage drop.
4. Stop Watch. A stop watch or clock accurate to 1 second should be used.
B. Test Procedure
1. The test should be performed in the room in which the detection system is installed, with all normal
ventilation fans (e.g., fans internal to equipment, room ventilation fans) operating. Testing should also be
performed with the fans turned off to simulate the potential for fan cycling and/or a power failure. This
does not preclude testing required by NFPA 72.
2. Detector Programming. The detector alarm sensitivity setting (i.e., pre-alarm or alarm) used during the
test should be identical to those used during normal operation of the detection system. Alarm verification
or time delay features should be disabled during the test to permit the detector response to be annunciated
immediately upon activation.
This testing is intended to verify that the detectors or sensor will ″see″ smoke in sufficient concentrations
to reach the specified alarm levels.
Because the test produces a small amount of smoke for a brief period of time (i.e., a puff of smoke), the
use of the alarm verification or time delay features would likely result in the detector or sensor not reaching
the specified alarm levels. In a ″real world″ fire, the smoke would continue to be produced as the fire
grows, permitting the detector or sensor to reach alarm. If these features are disabled during the testing,
they should be enabled at the conclusion of the testing before leaving the room.
3. Test Locations. Test locations should be selected by considering the airflow patterns in the room and
choosing challenging locations for the tests (i.e., both low airflow and high airflow can be challenging). If
possible, the locations and elevations of the test apparatus should be varied to simulate the range of
possible fire locations in the room. Locations where the smoke will be drawn directly into the data
processing equipment cooling ports or fans should be avoided. Locations where the smoke will be
entrained into the air exhausting from an equipment cabinet are acceptable.
4. Preparation. The test wire should be prepared by carefully removing not more than 0.6 in. (12 mm)
of the insulation from each end. The wire should be mounted on the insulating material so that there are
no kinks or crossovers in the wire.
5. Setting. The power supply should be set to supply either a constant voltage or constant current as
shown in Table C-2.
6. Connection. The ends of the test wire(s) should be connected to the power supply leads.
7. Test. When all other preparations are complete, the power supply should be switched on for a period
shown in Table C-2. After the appropriate current application time, the power supply should be turned
off, and the test results should be observed and recorded. To avoid burns, the wire should not be touched
during the test, or for 3 minutes after turning the power supply off. If the wire is located close to HVAC
registers or equipment exhaust ports, the airflow can cool the wire and result in inadequate production of
smoke. In this event, either the apparatus should be repositioned or the wire should be shielded from
the airflow.
8. Test Sequence. The test should be repeated at least three times for each HVAC condition, with the
test apparatus placed in a different location in the room each time. If possible, the elevation of the test
apparatus should be varied.
9. Pass/Fail Criteria. The pass or fail criteria for the VEWFD system should be as indicated in Table C-2.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

5-32 Data Centers and Related Facilities
Page 74 FM Global Property Loss Prevention Data Sheets

APPENDIX D CLEAN AGENTS

Clean agents listed in Tables D-1 and D-2 are typically used for electronic equipment applications. The
concentrations given for ordinary combustibles (Class A) and ignitable liquids (Class B) are accepted by NFPA
2001 based on their listing with the system manufacturer. The ignitable liquids (Class B) concentrations are
provided as a comparative reference to the other hazard concentrations.
For cables that could be de-energized, the design concentration required for an ordinary combustible (Class
A) would be used. Although electronic data processing equipment cannot be expected to be de-energized
quickly based upon certain risk factors. NFPA 2001 has recognized that a higher agent concentration should
be used for low energy faults (480 volts) by adding a safety factor of 1.35, determined by consensus, to
the ordinary combustible (Class A) extinguishing concentration.
FM Global Research has conducted testing that indicates still higher concentrations are needed for higher
energy arcing faults. This is due to the effect of the type of fault and power level (energy augmented
combustion) has on the ability to attenuate the energized source. However, it is an indication that higher
design concentrations for energized electrical equipment are expected and a function of the power level.
If the fault is not de-energized before clean agent concentration is dissipated, re-ignition is expected. These
higher concentrations need to be reviewed for restrictions when used in normally occupied areas.

Table D-1. Design Concentrations for Clean Agents

Minimum Class A Design Minimum Class B Design
Concentration from Manual, Concentration from manual,
(Note 1) (Note 2)
Extinguishing Agent percent percent
FK-5-1-12 (NOVEC 1230) 4.2 5.8
HFC-125 (FE-25) 8.0 11.0
HFC-227ea (FM-200/FE-227)(Note 3) 6.25, 7.0 8.7, 9.0
IG-541 (INERGEN) 34.2 40.6
IG-55 (Argonite, ProInert) 37.9 39.1
Note 1. The minimum design concentration for ordinary combustible materials (Class A) can be used for an electrical ignition (Class C)
source with de-energizing of the source upon clean agent fire extinguishing system actuation.
Note 2. Ignitable liquids (Class B) design concentrations are based upon heptane as the fuel.
Note 3. The lower design concentration of the two is the result of a retest by the manufacturer. Refer to the Approval Guide listing for the
appropriate concentration.

Table D-2. Design Concentrations for Clean Agents with an Energized Electrical Hazard
Energized Class C, Energized Class C,
Extinguishing Agent percent ≤ 480V (Note 1) Percent > 480V (Note 2)
FK-5-1-12(NOVEC 1230) 4.7 10
HFC-125 (FE-25) 9.0 20
HFC-227ea(FM-200/FE-227) 7.0, 7.8 12
IG-541 (INERGEN) 38.5 57
IG-55 (Argonite, ProInert) 42.7 Not Tested
Note 1. Refer to the Approval Guide listing for the appropriate concentration.
Note 2. FM Global conducted testing that indicates higher agent concentrations are needed for high-energy arcing faults. Only certain clean
agents were tested. Refer to Section 3.3 for additional information on this testing. Where an agent is listed as “not tested,” additional
testing isnecessary if the clean agent system is intended to protect energized electrical hazards greater than 480 volts that remain
energized following discharge. Do not use an agent to protect high-energy electrical hazards if this testing has not been conducted.

These higher concentrations in Table D-2 need to be reviewed for restrictions when used in normally occupied
areas. See Section 3.2.4 and Table 5 of Data Sheet 4-9, Halocarbon and Inert Gas (Clean Agent) Fire
Extinguishing Systems, for information regarding No Observed Adverse Effects Limit (NOAEL) and Lowest
Observed Adverse Effects Limit (LOAEL).

APPENDIX E BIBLIOGRAPHY
British Standard Institute (BSI). Fire protection for electronic equipment installations - Code of practice, BS
6266:2011.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.

Data Centers and Related Facilities 5-32
FM Global Property Loss Prevention Data Sheets Page 75

Curtis, Peter M. Maintaining Mission Critical Systems in a 24/7 Environment. 2nd edition. Hoboken: John
Wiley & Sons, Inc, 2011.
European Norm (EN) 50600-2-5:2021. Information technology – Data centre facilities and infrastructures –
Part 2-5: Security systems.
European Norm (EN) 54-20:2006-09. Fire detection and fire alarm systems – Part 20: Aspirating smoke
detectors (includes Amendment AC:2008).
Hu, Pearl. “Electrical Distribution Equipment in Data Center Environments”, Schneider Electric, White Paper
61, Revision 1.
National Fire Protection Association (NFPA). National Electrical Code, NFPA 70, 2014.
National Fire Protection Association (NFPA). Protection of Information Technology Equipment, NFPA 75,
2020.
National Fire Protection Association (NFPA). Fire Protection of Telecommunications Facilities, NFPA 76, 2020.
Rath, John. Data Center Knowledge Guide to Modular Data Centers, October 2011.
Siemens Switzerland Ltd. Building Technologies. “Potential Problems with Computer Hard Disks when Fire
Extinguishing Systems Are Released.” 2010.
Siemens AG. “Silent Extinguishing, Disruption to hard disk drives caused by inert gas extinguishing systems
– analysis and measures for the safe operation of storage systems”, July 2021.
Thumuluru, S., Ditch, B., Chatterjee, P. and Chaos, M. Experimental Data for Model Validation of Smoke
Transport in Data Centers. Research Technical Report. FM Global. September 2014.
Tyco Fire Products. “INERGEN Acoustics Testing Position Paper.” 2012.
Uptime Technologies, LLC. Data Center Site Infrastructure Tier Standard: Topology. Uptime Institute
Professional Services, LLC, 2012.
Wagner Group GmbH. “FirExting® SILENT Product Information.” Issue 010/10.
Xtralis. Telecommunications and Data Processing Facilities - Design Guide, July 2007.

©2012-2023 Factory Mutual Insurance Company. All rights reserved.