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i 770-1

Updating of NFPA Staodards

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Users ofNFPA codes, standards, recommended practices, and guides ("NFPA Standards") should be aware that these
documents may be superseded at any time by the issuance of a new edition, may be amended with the issuance of Tentative
Interim Amendments (TIA<;), or be corrected by Errata. It is intended that through regular revisions and amendments,
participants in the NFPA standards development process consider the then-current and available information on incidents,
NFPA® 770
materials, technologies, innovations, and methods as these develop over time and that NFPA Standards reflect this
consideration. Therefore, any previous edition of this document no longer represents the current NFPA Standard on the
subject matter addressed. NFPA encourages the use of the most current edition of any NFPA Standard [as it may be amended Srandardon
by TIA(s) or Errata] to take advantage of current experience and understanding. An official NFPA Standard at any point in
time consists of the current edition of the document, including any issued TIAs and Errata then in effect. Hybrid (Water and Inert Gas) Fire-Extinguishing Systems
To determine whether an NFPA Standard has been amended through the issuance ofTIAs or corrected by Errata, visit the
"Codes & Standards" section at ·w1vw.nfpa.org. 2021 Edition
Interpretations of NFPA Standards This edition of NFPA 770, Standard on Hybrid (Water and Inert Gas) Fire-Extinguishing Systems, was
A statement, written or oral, that is not processed in accordance with Section 6 of the Regulations Governing the prepared by the Technical Committee on Hybrid (Water and Inert Gas) Fire Extinguishing Systems.
Development of NFPA Standards shall not be considered the official position of NFPA or any of its Committees and shall not It was issued by the Standards Council on March 15, 2020, with an effective date of April 4, 2020.
be considered to be, nor be relied upon as, a Formal Interpretation.
This edition of NFPA 770 was approved as an American National Standard on April 4, 2020.
Patents
Origin and Development of NFPA 770
The NFPA does not take any position w-ith respect to the validity of any patent rights referenced in, related· to, or asserted in
connection with an NFPA Standard. The users of NFPA Standards bear the sole responsibility for determining the validity of Since the signing of the 1989 Montreal Protocol, the fire protection industry has innovated
any such patent rights, as well as the risk of infringement of such right'>, and the NFPA disclaims liability for the infringement continually to find effective alternatives to Halons for special applications. This pursuit has resulted
of any patent resulting from the use of or reliance on NFPA Standards. in the proliferation of fire protection systems using various extinguishing agents, including
halocarbon clean agents, inert gas clean agents, water mist, and fire-extinguishing aerosols. Since
NFPA adheres to the policy of the American National Standards Institute (ANSI) regarding the inclusion of patenl'> in
each of these extinguishing agents has inherent limitations, it was recognized that some of these
American National Standards ("the ANSI Patent Policy"), and hereby gives the following notice pursuant to that policy:
limitations could be offset by combining multiple agents. By the early 2000s, system manufacturers
NOTICE: The user's attention is called to the possibility that compliance with an NFPA Standard may require use of an discovered that a hybrid media of fine water mist and inert gas agent provides a unique set of
invention covered by patent righL'>. NFPA takes no position as to the validity of any such patent rights or as to whether such characteristics that are ideal for dispersion, extinguishment, and cooling.
patent rights constitute or include essential patent claims under the ANSI Patent Policy. If, in connection w-ith the ANSI Patent
Following the introduction of hybrid fire-extinguishing systems to the commercial market in
Policy, a patent holder has filed a statement of willingness to grant licenses under these rights on reasonable and
2008, the technical committees responsible for NFPA 750, Standard on Water Mist Fire Protection
nondiscriminatory terms and conditions to applicants desiring to obtain such a license, copies of such filed statements can be
Systems, and NFPA 2001, Standard on Clean Agent Fire Extinguishing System5, reviewed the technology for
obtained, on request, from NFPA. For further information, contact the NFPA at the address listed below.
possible inclusion in the scopes of their standards. Both committees determined that either the
Law and Regulations gaseous component or the water component, respectively, introduced an element that was
incompatible with the scope of their work.
Users ofNFPA Standards should consult applicable federal, state, and local laws and regulations. NFPA does not, by the
publication of its codes, standards, recommended practices, and guides, intend to urge action that is not in compliance with The NFPA received the request for a new project on hybrid (water and inert gas) fire-
applicable laws, and these document'> may not be construed as doing so. extinguishing systems in September 2012. In March 2013, the NFPA Standards Council issued a
request for public comment and received a positive response that a project should be initiated.
Copyrights Subsequently, the Fire Protection Research Foundation launched a research project to compare
NFPA Standards are copyrighted. They are made available for a wide variety of both public and private uses. These include hybrid extinguishing with other technologies to determine wh~ther any of the existing technical
both use, by reference, in laws and regulations, and use in private self:.regulation, standardization, and the promotion of safe committees could take responsibility for the new topic. Based largely on research by FM Global, the
practices and methods. By making these documents available for use and adoption by public authorities and private users, the final report, issued in May 2014, concluded that hybrid systems represent a separate and distinct
NFPA does not waive any rights in copyright to these documents. technology from either water mist or clean agent systems and recommended that a new, separate
document should be developed. In October 2014, the Standards Council approved the project and
Use of NFPA Standards for regulatory purposes should be accomplished through adoption by reference. The term called for members. A committee was appointed and met for the first time in September 201E,.
"adoption by reference" means the citing of title, edition, and publishing information only. Any deletions, additions, and
changes desired by the adopting authority should be noted separately in the adopting instrument. In order to assist NFPA in Over the course of the next two years, the Technical Committee on Hybrid (Water and Inert Gas)
following the uses made of its documents, adopting authorities are requested to notify the NFPA (Attention: Secretary, Fire Extinguishing Systems met five times to develop a draft standard. These early meetings included
Standards Council) in writing of such use. For technical assistance and questions concerning adoption of NFPA Standards, detailed and often contentious debates on important topics, such as the definition of the term hybrid
contact NFPA at the address below. media, the system design method, the application of design safety factors, system application testing
and design validation, and hybrid media retention time.
For Further Information
In December 2017, the technical committee submitted a final draft to the Standards Council for
All questions or other communications relating to NFPA Standards and all requests for information on NFPA procedures public review, and the draft was placed in the Annual 2020 revision cycle. In accordance with NFPA's
governing its codes and standards development process, including information on the procedures for requesting Formal standards development process, the committee incorporated two rounds of public feedback to
Interpretations, for proposing Tentative Interim Amendments, and for proposing revisions to NFPA standards during regular further refine and expand the standard.
revision cycles, should be sent to NFPA headquarters, addressed to the attention of the Secretary, Standards Council, NFPA, 1
Batterymarch Park, P.O. Box 9101, Quincy, MA02269-9101; email: stds_admin@nfpa.org. / This first edition of NFPA 770, Standard on Hybrid (Water and Inert Gas) Ji'ire-Extinguishing Systems, is
the result of years of volunteer service by intelligent, thoughtful, and dedicated professionals,
For more information about NFPA, visit the NFPA website at www.nfpa.org. All NFPA codes and standards can be viewed at including the technical committee members listed on the following page. However, the list does not
no cost at www.nfpa.org/ docinfo. fully reflect all of the key contributors who donated their time, knowledge, and experience to the
process. In recognition of those volunteers, special thanks are extended to Thomas Wysocki, Hong-
Zeng (Bert) Yu, Kevin Kelly, Steve Owens, Kevin Murray, Adam Tracy, and Robert Upson.

NFPA and National Fire Protection Association arc registered trademarks of the National Fire Protection Association, Qulocy, ·Massachusel[S 02169.
 770-2 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS CONTENTS 770-3

Technical Committee on Hybrid (Water and Inert Gas) Fire Extinguishing Systems Contents
Jeffrey L. Harrington, Chair
Chapter 1 Administration . 770-4 9.3 Nozzle Selection, Quantity, and Location .. 770-- I 7
Harrington Group, Inc., GA [SE]
1.1 Scope. 770-4 9.4 Discharge Rate. 770-- 17
Thomas G. Euson, Secretary ] .2 Purpose. 770-4 9.5 Discharge Time. 770- 17
3S Incorporated, IN [IM] 13 Retroactivity. 770-4 9.6 Hybrid Media Quantity. 770- 17
1.4 Equivalency.. 770-4
RobertJ. Ballard, Victaulte, PA [M] 1.5 Units of Measurement. 770- 4 Chapter 10 Design Requirement.s for Marine Systems
Shawn Mullen, Protex Central, Inc., IA [M]
Rep. Fire Suppression Systems Association (Reserved) . 770- 18
Frank Broidy, Fire & Pump Seniice Group, CA [IM]
Chapter 2 Referenced Publications . 770-5
John D. Campbell, Global Fire Protection Group, LLC, MO [SE] Rob Plonski, Savannah River National Laboratory, GA [U] Chapter 11 System Documentation . 770- 18
2.1 General. 770-5
Jason Chou, UTC/Marioff/Ktddc, MA [M] James H. Sharp, Siemens Energy, FL [MJ 2.2 NFPA Publications. 770-- 5 11.l System Working Plans. 770-- 18
Brent S. Ehmke, Ehmke A~sociates, NC [SE] Blake M. Shugarman, UL LLC, IL [RT] 2.3 Other Publications .. 770:-- 5 11.2 System Flow Documentat1on. 770-- 18
Eric W. Forssell,JENSEN HUGHES, MD [SE] Matthew G. Taylor, Mitsubishi Hitachi Power Systems, FL [U] 2.4 References for Extracts in Mandatory Sections. 770-6 11 3 Detect1on, Actuation, and Control Systems
Rep.JENSEN HUGHES James W. Turner, Road Sprinkler Fitters UA Local Union 669, NJ Documentation. 770- 19
Walter Groden, AJG Global Technical Office, NY [I] [L] Chapter 3 Definitions . 770-6 11.4 Owner's Documentation .. 770- 19
Rep. UnitedA~sn. ofJourneymen &Apprentices of the 3.1 General. 770-6 11.5 System lnfonnation Sign .. 770- 19
IanJutras,Johnson Controls, RI [M]
Plumbing & Pipe Fitting Industr;' 3.2 NFPA Official Definitions. 770-6
Robert Kasiski, FM Global, N[A. [11 3.3 General Definitions . 770- 6 Chapter 12 Installation Requirements . 770- 19
David Lindenschmidt, Duke Energy, OH [U J 12.l General. 770- 19
Rep. Edison Electric Institute Chapter 4 General Information . 770-7 12.2 Nozzles .. 770-- 19
4.1 Use and Limttatiom. 770-- 7 12.3 Hazardous Locations. 770- 19
Alternates 4.2 Safety Considerations. 770-- 8 12.4 Electrical Clearances. 770-- 19
TimJ. Anderson, Savannah River Nuclear Solutions, LLC, SC [U] Justin A. Perry, Dominion Energy, VA [U]
4.3 Use Restrictions . 770-8 12.5 Pipe Network. 770- 19
(Alt. to Rob Plonski) (Alt. to DaVJd Lindenschrnidt) 4.4 Qualifications. 770-8 12.6 Gas and Water Storage Containers. 770- 20
12.7 Valves and Pressure Gauges. 770- 20
Joseph C. Barter, UTC/Manoff North America, MA [M] Kenneth R. Schneider, UA- ITF, MO [LJ Chapter 5 Component.s . 770-8
(Alt. to Jason Chou) (Alt. to James W. Turner)
12.8 Electrical Equipment and Systems. 770- 20
5.1 Water Supply. 770- 8 ] 2.9 System Review and Testing. 770- 21
Lawrence R. Carmen, Victaulic Company of America, PA [M] Daniel R. Steppan, UL LLC, IL [RTJ 5.2 Inert Gas Agent Supply. 770- 8
(Alt. to Robert]. Ballard) (Alt. to Blake M Shugarman) 5.3 Storage Contamers. 770-8 Chapter 13 Acceptance Testing. 770-- 21
Jonathan E. Carpenter, FM Global (FM Approvals), RI [I] Ben R. Stewart, Western States Fire Protection, SD [M] 5.4 Pipe, Fittings, and_ Valves. 770-9 13.1 Approval oflnstallat.Ions. 770-- 21
(Alt. to Robert Kasiski) (Voting Alt.) 5.5 Hybrid Nozzles. 770- IO 13.2 Acceptance Requirements .. 770-21
Sean Cutting,Johnson Controls, RI [M] Brandon M. Troe, Fire & Pump Service Group, CA [IMJ 5.6 Detect.Ion, Actuation, Alarm, and Control 13.3 System Design Information Sign. 770- 22
(Alt. to Ian Jutras) (Alt. to Frank Broidy) Systems .. 770- II 13.4 Owner's Documentation. 770- 22
Jeff L. Hausmann, Fire Equipment Company Inc., MI [MJ Tom Zornes, Siemens, IN [M]
(Alt. to Shawn Mullen) (Alt. to James H. Sharp) Chapter 6 Application and Fire Test Protocols . 770-- 13 Chapter 14 Inspection, Testing, and Maintenance . 770- 22
Aaron C. Hinkle, 3S Incorporated, IN [IM] 6.1 General. 770-- 13 14.1 General. 770-- 22
(Alt. to Thomas G. Euson) 6.2 Listing or Approval Evaluations 770-13 14.2 Periodic Inspection and Maintenance. 770-- 23
6.3 Performance Objectives. 770- 13 14.3 Hose Test. 770-23
Barry D. Chase, NFPA Staff Lmson 6.4 Application Parameters. 770- 13 14.4 Inert Gas Agent Container Test. 770- 23
6.5 Floodmg Factor.. 770- 14 14.5 Water Storage Container Inspection and Test. 770- 24
This list represenl~ the ·membership at the time the Committee was balloted on the final text of this edition. 14.6 Actuation/Impairment. 770- 24
Since that time, changes in the m,.,,mbership may have occurred. A key to classifications is found at the Chapter 7 System Design Requirement.s .. 770-- 14 14.7 Training. 770- 24
back of the document. 7.1 General.. 770-- 14 14."8 Corrections and Repairs. 770-- 24
7.2 Pipe Network Layout and Design. 770-14
NOTE: Membership on a committee shall not in and of itself constitute an endorsement of Chapter 15 Impairment . 770-24
the Association or any document developed by the committee on which the member sen;es. Chapter 8 Design Requirement.s for Total Flooding 15.1 General 770- 24
Systems. 770- 14 15.2 Impairment Coordinator.. 770- 24
Committee Scope: This committee shall have pnmary responsibility for documents covering 8.1 General. . 770-- I 4 15.3 Tag Impairment System. 770- 24
the design, installation, operation, and maintenance of hybnd (water and inert gas) fire 82 Enclosure Requirements. 770-- 15 15.4 Impaired Equipment. 770- 25
extinguishing systems that use a combination of atomized water and inert gas to extinguish 8.3 System Performance Characteristics. 770-- I 5 15.5 Preplanned Impairment Programs 770-- 25
fire. This scope does not include systems that use only mert gas or only atomized water 8.4 Hybrid Media Quantity. 770- 15
(water mist) to achieve extinguishment. It also does not include hvin fluid water 1mst systems
15.6 Emergency Impairments. 770-25
8.5 Concentration of Oxygen. 770-16 15.7 Restoring Systems to Service. 770-25
that use inert gas to propel and/or atomize water mist droplets without generating a 8.6 Hybrid Media Retention for Prevention ofRe-
significant inert gas concentration in the protected space.
igrntion .. 770- 16 Annex A Explanatory Material .. 770- 25
8.7 Hybrid Nozzle Seleclion, Quantity, and
Location 770-- 16 Annex B Fire Test Methods . 770-- 33

Chapter 9 Design Requirement.s for Local Annex C Informational References . 770- 37

Application Systems .. 770- I 7
9.1 General.. 770- 17
Index 770- 38
9.2 Hazard Specifications. 770-- I 7

2021 Edition 2021 Edition

 ------------ ~

770-4 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS REFERENCED PUBLICATIONS 770-5

NFPA 770 1.2* Purpose. This standard is prepared for the use and guid- Table 1.5 Units of Measurement
ance of those charged with the purchasing, designing, mstal-
Standard on ling, testing, inspecting, approving, listing, operating, or Primary Unit Secondary Unit
maintaining of hybrid fire-extinguishing systems, in order that
Hybrid (Water and Inert Gas) Fire- such equipment will function as intended throughout its life. Measurement Name Symbol Name Symbol

Extinguishing Systems 1.3 Retroactivity. The provisions of this standard reflect a Area, surface square meters m' square feet ft'.!
consensus of what is necessary to provide an acceptable degree Distance, general meters m feet ft
2021 Edition of protection from the hazards addressed in this standard at Distance, orifice diameter/droplet size micrometers µm inches in.
the time the standard was issued. Distance, pipe/tube dimensions millimeters mm inches in.
IMPORTANT NOTE: This NFPA document is made available for 1.3.1 Unless otherwise specified, the design, installation, and
Mass, general kilograms kg pounds (mass) lb
Pressure, atmospheric millimeters of mercury mm Hg inches of mercury in. Hg
use subject to important notices and legal disclaimers. These notices acceptance requirements of Chapter 4 through Chapter 13
and disclaimers appear in all publications containing this document Pressure, system/nozzle bar bar pounds per square inch psi
shall not apply to facilities, equipment, structures, or installa- oy
and may be found under the heading "Important Notices and tions that existed or were approved for construction or installa- Temperature degrees Celsius 'C degrees Fahrenheit
Disclaimers Concerning NFPA Standards. " They can also be viewed tion prior to the effective date of the standard. Time, general minutes minutes minutes minutes
at www.nfpa.org/disclaimers or obtained on request from NFPA. Time, discharge/extinguishment seconds seconds seconds seconds
1.3.2 Unless otherwise specified, inspection, testing, and Time, inspection interval months months months months
UPDATES, ALERTS, AND FUTURE EDITIONS: New editions of
maintenance requirements in Chapter 14 shall apply to new Time, maintenance interval years years years years
NFPA codes, standards, recommended practices, and guides (i.e.,
and existing facilities, equipment, structures, or installations. Volume, enclosure/inert gas cubic meters m' cubic feet ft~
NFPA Standards) are released on scheduled revision cycles. This
edition may be superseded by a later one, or it may be amended 1.3.3 In those cases where the authority having jurisdiction Volume, water liters L gallons gal
outside of its scheduled revision cycle through the issu,ance of Tenta- determines that an existing situation presents an unacceptable
tive Interim Amendments (TIAs). An official NFPA Standard at any degree of risk, the authority having jurisdiction shall be permit-
point in time consists of the current edition of the document, together 1.5.3 Measurement of Pressure. All measurements of pres- ASME B31.l, Power Piping, 2018.
ted to apply retroactively any portions of this standard.
tuith all TIAs and Errata in effect. To verify that this document is the sure are gauge values, unless otherwise noted.
Boiler and Pres.mre Vessel Code, 201 7.
current edition or to determine if it has been amended by TIAs or 1.3.4 Requirements that are retroactively applied in accord-
1.5.4 Unit Application and Enforcement.
Errata, please consult the National Fire Codes® Subscription Sentice ance with this standard shall be permitted to be modified if 2.3.3 ASTM Publications. ASTM International, 100 Barr
or the "List of NFPA Codes & Standards" at www.nfpa.org/docinfo. their application clearly would be impractical in the judgment 1.5.4.1 * The values presented in this standard are expressed Harbor Drive, P.O. Box C700, West Conshohocken, PA
In addition to TIAs and Errata, the document information pages also of the authority having jurisdiction, and only where it is clearly with a degree of precision that is appropriate for practical 19428-2959.
include the option to sign up for alerts for individual documents and evident that a reasonable degree of safety is provided. application and enforcement.
ASTM A53/ A53M, Standard Specification for Pipe, Steel, Black
to be involved in the development of the next edition. 1.4 Equivalency. Nothing in this standard is intended to 1.5.4.2* Either the primary units or secondary units arc and Hot-Dipped, Zinc-Coated, Welded and Seamless, 2018.
NOTICE: An asterisk (*) following the number or letter prevent the use of systems, methods, or devices of equivalent or acceptable for satisfying the requirements in this standard.
designating a paragraph indicates that explanatory material on superior quality, strength, fire resistance, effectiveness, durabil- ASTM Al06/Al06M, Standard Specification for Seamless Carbon
the paragraph can be found in Annex A ity, and safety over those prescribed by this standard. Steel Pipe fOr High-Temperature Service, 2018.
A reference in brackets [ ] following a section or paragraph Chapter 2 Referenced Publications
indicates material that has been extracted from another NFPA 1.4.1 Technical documentation Shall be submitted to the ASTM A269/A269M, Standard Specification for Seamless and
document. Extracted text may be edited for consistency and authority having jurisdiction to demonstrate equivalency. 2.1 General. The documents or portions thereof listed in this Welded Austenitic Stainless Steel Tubing for General Service, 2015a.
style and may include the revision of internal paragraph refer- chapter are referenced within this standard and shall be ASTM A312/ A312M, Standard Specification for Seamless,
1.4.2 The system, method, or device shall be approved for the
ences and other references as appropriate. Requests for inter- considered part of the requirements of this document. Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes,
intended purpose by the authority having jurisdiction.
pretations or revisions of extracted text shall be sent to the 2018.
2.2 NFPA Publications. National Fire Protection Association,
technical committee responsible for the source document. 1.5 Units of Measurement. The units of measurement used in
1 Batterymarch Park, Quincy, MA 02169-7471. ASTM A632, Standard Specification for 5,'earnless and Welded
Information on referenced and extracted publications can this standard are in accordance with Table l.5.
be found in Chapter 2 and Annex C. NFPA 13, Standard for the Installation of Sprinkler System.~, 2019 Austenitic Stainless Steel Tubing (Small-Diameter) for General Service,
1.5.1 Primary Units. Primary units of measurement are in edition. 2004, reapproved 2014.
accordance with the modernized metric system known as the
Chapter 1 Administration International System of Units (SI), except where specific units NFPA 7rJE', National Electrical Co~, 2020 edition. ASTM A778/ A778M, Standard Specification for Welded, Unan-
are customary for industry practice. nealed Austenitic Stainless Steel Tubular Products, 2016.
1.1 Scope. This standard contains the minimum require- NFPA 7'?, National Nre 1llarm and Signaling Code®, 2019
1.5.2 Secondary Units and Conversions. edition. ASTM A789/A789M, Standard Specification fOr Seamless and
ments for the design, installation, acceptance, inspection, test- Welded Ferntic/Austenitic Stainless Steel 1Ubing for General Service,
ing, and maintenance of hybrid fire-extinguishing systems that 1.5.2.1 Secondary units of measurement, where provided, are NFPA 750, Standard on Water Mist Fire Protection Systems, 2019 2018.
use a combination of atomized water and inert gas to extin- in accordance with U.S. customary units (inch-pound units), edition.
guish fire. except where specific units are customary for industry practice. ASTM B75/B75M, Standard Specification for Seamless Copper
NFPA 200 l, Standard on Clean Agent Fire Extinguishing Systems, Tube, 2011.
1.1.1 The scope of this standard does not include systems that 1.5.2.2 "Where secondary units are not provided, converted 2018 edition.
use only inert gas to achieve extinguishment. (See NFPA 2001.) values and converted trade sizes can be used. ASTM B88, Standard Specification for Seamless Copper Water
2.3 Other Publications. Tube, 2016.
1.1.2 The scope of this standard does not include systems that 1.5.2.3 Where extracted text contains values expressed in only
use only atomized water (water mist) to achieve extinguish- one system of, units, the values in the extracted text have been 2.3.1 ANSI Publications. American National Standards Insti- ASTM B251/B251M, Standard Specification for General Require-
ment. (See NFPA 750.) retained without conversion ~o preserve the values established tute, Inc., 25 West 43rd Street, 4th Floor, New York, NY 10036. ments for Wrought Seamless Capper and Capper-Alloy 1Ube, 201 7.
1.1.3 The scope of this standard does not include twin fluid by the responsible technica1 committee in the source docu- ANSI Z535.2, Standard for Environmental and Facility Safety 2.3.4 CGA Publications. Compressed Gas Association, 14501
water mist systems that use inert g-as to propel and/ or atomize ment. Signs, 20ll, reaffirmed 2017. George Carter Way, Suite 103, Chantilly, VA 20151-2923.
water mist droplets without generating a significant inert gas
2.3.2 ASME Publications. American Society of Mechanical CGA C-6, Standard for Visual Inspection of Steel Compressed Gas
concentration in the protected space. (See N}PA 750.)
Engineers, Two Park Avenue, New York, NY 10016-5990. Cylinde,-s, 2013.
ASME Bl.20.1, Pipe Threads, General Purpose, Inch, 2013.

2021 Edition 2021 Edition

 770-6 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS GENERAL INFORMATION 770-7

2.3.5 ISO Publications. International Organization for Stand- standards or has been tested and found suitable for a specified 3.3.4.3 Uooccupiable Enclosure or Space. An enclosure or pressure of oxygen matches the ambient partial pressure of
ardization, ISO Central Secretariat, BIBC II, Chemin de Blan- purpose. space that has dimensions and physical characteristics such oxygen at a given altitude. [2001, 2018]
donnet 8, CP 401, 1214 Vernier, Geneva, Switzerland. that it could not be entered by a person. [12, 2018]
3.2.5 Shall. Indicates a mandatory requirement. 3.3.14 Pressure.
ISO 7-1, Pipe threads where pressure-tight joints are made on the 3.3.5 Fire Extinguishment. The complete extinction of a fire
threads - Part 1: Dimensions, tolerances and designations, 1994, 3.2.6 Should. Indicates a recommendation or that which is 3.3.14.1 Maximum Allowable Working Pressure. The maxi-
and all burning combustibles.
reconfirmed 2015. 'advised but not required. mum pressure to which a system can be suqjected without
3.3.6 Hybrid Fire-Extinguishing System. A tire-extinguishing exceeding the pressure rating of any of its component parts.
2.3.6 U.S. Government Publications. U.S. Government 3.2.7 Standard. An NFPA Standard, the main text of which
system capable of delivering hybrid media at the specified
Publishing Office, 732 North Capitol Street, NW, Washington, contains only mandatory provisions using the word ''shall" to 3.3.14.2* Maximum operating Pressure. The maximum pres-
design rate and proportion.
DC 20401-0001. indicate requirements and that is in a form generally suitable sure to which pipe or components will be subjected, deter-
for mandatory reference by another standard or code or for 3.3.7* Hybrid Media. An extinguishing media created by the mined at the maximum listed storage temperature.
Title 29, Code of Federal Regulations, Part 1910, "Occupa- adoption into law. Nonmandatory provisions are not to be simultaneous discharge of water mist and an inert gas agent in
tional Safety and Health Standards." considered a part of the requirements of a standard and shall a controlled proportion from a common discharge device that 3.3.15 System Design Methods.
be located in an appendix, annex, footnote, informational results in an oxygen concentration less than 16 percent. 3.3.15.1 Engineered Systems. Those systems for which flow
2.3.7 Other Publications.
note, or other means as permitted In the NFPA Manuals of rates, quantities of extinguishing agent, pipe size, pipe
Style. "When used in a generic sense, such as in the phrases 3.3.8 Hybrid Nozzle. A special purpose device con taming one
Merriam Webster's Collegiate Dictionary, 11th edition, Merriam lengths, fittings, and size, type, and placement of nozzles are
"standards development process" or "standards development or more orifices specifically designed to deliver the hybrid
Webster, Inc., Springfield, MA, 2003. determined by individual design and calculation based on
activities", the term "standards" includes all NFPA Standards, media to the fire.
individual hazard volume, configuration, and fuel loading.
2.4 References for Extract-. in Mandatory Sections. including Codes, Standards, Recommended Practices, and 3.3.9* hnpairment. A condition where a fire protection
Guides. system or unit or portion thereof is out of order, and the condi- 3.3.15.2* Pre-Engineered Systems. Those systems having
NFPA 12, Standard on Carbon Dioxide Extinguishing Systems,
tion can result in the fire protection system or unit not func- predetermined flow rates and quantities of extinguishing
2018 edition. 3.3 General Definitions
tioning in a fire event. [25, 2017] agent with specific pipe sizes, maximum and minimum pipe
NFPA 25, Standard f0r the Inspection, Testing, and Maintenance 3.3.1 Classes of Fire. lengths, flexible-hose specifications, number of fittings, and
of Water-Based Fire Protection Systems, 201 7 edition. 3.3.9.1 * Emergency Impairment. A condition where a· fire number, type, and locations of nozzles listed for specific
3.3.1.1 Class A Fire. A fire in ordinary combustible materi- protection system or portion thereof is out of order due to hazards of predetermined volume and fuel loading.
NFPA 750, Standard on Water Mist Fire Protection Systems, 2019 als, such as wood, cloth, paper, rubber, and many plastics. an unplanned occurrence, or the impainnent is found while
edition. performing inspection testing or maintenance activities. 3.3.16 Water Mist. A water spray for which the Dv0_99 for the
3.3.1.2 Class B Fire. A fire in flammable liquids, combusti- flow-weighted cumulative volumetric distribution of water
NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems, [25, 2017]
ble liquids, petroleum greases, tars, oils, oil-based paints, droplet<; is less than 1000 µm within the nozzle operating pres-
2018 edition. solvents, lacquers, alcohols, and flammable gases. 3.3.9.2 Preplanned Impairment. A condition where a fire sure range. [750, 2019]
protection system or a portion thereof is out of service due
3.3.1.3 Class C Fire. A fire that involves energized electrical 3.3.17 Working Plans. Documentation used for review and
Chapter 3 Definitions to work planned in advance, such as revisions to the water
equipment. installation of the fire protection system. (See Chapter 1 I.)
supply or sprinkler system piping.
3.1 General. The definitions contained in this chapter shall 3.3.2 Deficiency. For the purposes of inspection, testing, and
3.3.10 Inert Gas Agent. An agent that contains as primary
apply to the terms used in this standard. Where terms are not maintenance of fire protection systems, a condition that will or Chapter 4 General Information
components one or more of the gases helium, neon, argon, or
defined in this chapter or within another chapter, they shall be has the potential to adversely impact the performance of a
nitrogen. Inert gas agents that are blends of gases can also
defined using their ordinarily accepted meanings within the system or portion thereof but does not rise to the level of an 4.1 Use and Limitations.
contain carbon dioxide as a secondary component. [2001,
context in which they are used. Merriam-Webster's Collegiate impainnent.
2018] 4.1.1 Hybrid systems shall be permitted to be used to extin-
Dictionary, 11th edition, shall be the source for the ordinarily
3.3.2.1 Critical Deficiency. A deficiency that, if not correc- guish Class A, Class B, and Class C fires in accordance with the
accepted meaning. 3.3.11 Inspection, Testing, and Maintenance.
ted, can have a material effect on the ability of the fire listing or fire test data that is acceptable to the authority having
3.2 NFPA Official Definitions. protection system or unit to function as intended in a fire 3.3.11.1 Inspection. A visual examination of a system or jurisdiction.
event. [25, 2017] portion thereof to verify that it appears to be in operating
3.2.1 * Approved. Acceptable to the authority having jurisdic- condition and is free of physical damage. 4.1.2 For Class C fires, electrical power to the protected
tion. 3.3.2.2 Noncritical Deficiency. A deficiency that does not hazard shall be shut down prior to the start of discharge, unless
have a material effect on the ability of the fire protection 3.3.11.2 Maintenance. Work, including, but not limited to, protection of energized electrical equipment is acceptable to
3.2.2* Authority Having Jurisdiction (AH)). An organization, system or unit to function in a fire event, but correction is repair, replacement, and service, performed to ensure that the authority having jurisdiction.
office, or individual responsible for enforcing the requirements needed to meet the requirements of this standard or for the equipment operates properly.
of a code or standard, or for approving equipment, materials, proper inspection, testing, and maintenance of the system 4.1.3* Hybrid systems shall not be used on fires involving the
an installation, or a procedure. or unit. [25, 2017] 3.3.11.3 Testing. Periodic operation of a component or following materials unless the hybrid media has been tested to
system to determine operational status. the satisfaction of the authority having jurisdiction:
3.2.3 Labeled. Equipment or materials to which has been 3.3.3 Dvr A drop diameter such that the cumulative volume,
attached a label, symbol, or other identifying mark of an organ- 3.3.12 Lockout Valve. A manually operated valve that can be (1) Certain chemical~ or mixtures of chemicals, such as cellu-
from zero diameter to this respective diameter, is the fraction,
iza.tion that is acceptable to the authority having jurisdiction locked in the closed position and that is supervised. lose nitrate and gunpowder, which are capable of rapid
f, of the corresponding sum of the total distribution. [750,
and concerned with product evaluation, that maintains peri- oxidation in the absence of air
2019] 3.3.13 Occupant Safety.
odic inspection of production of labeled equipment or materi- (2) Chemicals capable of undergoing autothennal decompo-
als, and by whose labeling the manufacturer indicates 3.3.4 Enclosures. 3.3.13.1 Lowest Observable Adverse Effect Level (LOAEL). sition, such as certain organic peroxides and hydrazine
compliance with appropriate standards or performance in a The lowest concentration at which an adverse physiological (3) Water-reactive materials, including, but not limited to, the
3.3.4.1 Normally Occupied Enclosure or Space. An enclosure following:
specified manner. . or toxicological effect has been observed. [2001, 2018]
or space where one or rp:ore persons are present under
3.2.4* Listed. Equipment, materials, or services included in a normal conditions. [2001: 2018] (a) Reactive _metals such as lithium, sodium, potas-
3.3.13.2 No Observed Adverse Effect Level (NOAEL). The
list published by an organization that is acceptable to the sium, magnesium, titanium, zirconium, uranium,
3.3.4.2 Occupiable Enclosure or Space. An enclosure or space highest concentration at which no adverse toxicological or
authority having jurisdiction and concerned with evaluation of and plutonium
that has dimensions and physical characteristics such that it physiological effect has been observed. [2001, 2018]
products or seni.ces, that maintains periodic inspection of (b) Metal hydrides
could be entered by a person. [2001, 2018] 3.3.13.3 Sea Level Equivalent of Oxygen. The oxygen concen- (c) Metal alkoxides, such as sodium methoxide
production of listed equipment or materials or periodic evalua-
tion of services, and whose listing states that either the equip- tration (volume percent) at sea level for which the partial (d) Metal amides, such as sodium amide
ment, material, or service meets appropriate designated (e) Carbides, such as calcium carbide

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I

I
 770-8 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS COMPONENTS 770-9

(f) Halides, such as benzoyl chloride and aluminum permitted in normally unoccupied areas when exposure time 5.3.1.2 Water storage containers shall be fabricated of 5.3.10 Containers meant to be transported while pressurized
chloride can be limited to 30 seconds. corrosion-resistant material or be provided with a corrosion- shall meet the requirements of the national codes_ for the coun-
(g) Hydrides, such as lithium aluminum hydride resistant interior coating. try of use.
(h) Oxyhalides, such as phosphorus oxybromide 4.3.3 Unoccupiable Areas. Hybrid systems with sea level
(i) Silanes, such as trichloromethylsilane equivalent oxygen concentrations of8 percent or lower shall be 5.3.2 Storage containers and accessories shall be located and 5.3.11 The design pressure for containers meant to be trans-
U) Sulfides, such as phosphorus pentasulfide permitted in unoccupiable areas. arranged to facilitate inspection, testing, recharging, and other ported while pressurized shall be suitable for the maximum
(k) Cyanates, such a'> methylisocyanate maintenance. pressure developed at the maximum listed temperature.
4.3.4* An egress time study shall be performed to verify that
4.1.4 Pre-Engineered Systems. All pre-engineered systems the maximum exposure time limits in 4.3. l and 4.3.2 are 5.3.3 Storage containers shall not be located where they are 5.3.12 Containers not covered in 5.3.10 shall be designed,
shall be installed to protect hazards -within the limitations that achieved. subject to severe weather conditions or to mechanical, chemi- fabricated, inspected, certified, and stamped in accordance
have been established by the listing. Provisions of this standard cal, or other damage. with Section VIII of the ASME Boiler and Pressure Vessel Code.
4.3.5* Altitude Considerations. In considering the oxygen
regarding personnel safety, commissioning, inspection, testing, concentration developed by a hybrid sysLem, the effect of alti- 5.3.3.1 Where exposure to severe weather conditions or to 5.3.13 The design pressure for containers not covered in
and maintenance shall apply. tude on oxygen concentration shall be considered for eleva- mechanical, chemical, or other damage cannot be avoided, 5.3.10 shall be suitable for the maximum pressure developed at
4.1.5 Temperature Limits. Hybrid system equipment shall be tions that vary from sea level by more than 915 m (3000 ft). approved safeguards or enclosures shall be provided. the maximum listed temperature.
designed to function from 4 °C Lo 54 °C (40°F to 130°F) or 4.3.6 "\,\!here the resulting sea level equivalent oxygen concen- 5.3.3.2 External heating or cooling shall be permitted to be 5.4 Pipe, Fittings, and Valves.
marked to indicate temperature limitations. tration is below the permitted limits for a system protecting a used to keep the temperature within the listed temperature
normally occupied or occupiable enclosure or space, the range. 5.4.1 General.
4.2* Safety Considerations.
following safeguards shall be provided: 5.4.1.1 Pipe, tubing, fittings, and valves shall be compatible
4.2.1 Unnecessary exposure to atmospheres flooded by a 5.3.4 Storage containers shall be installed and mounted m
( 1) Predischarge alarm accordance with the manufacturer's installation manual. with the manufacturer's hardware and media, as identified in
hybrid system resulting in low oxygen atmospheres shall be the listing and installation instructions, and with the intended
(2) Predischarge delay
avoided.
( 3) Warning signs 5.3.5 Each pressurized container or cylinder shall be provided environment.
4.2.2 Suitable safeguards shall be provided to ensure prompt (4) Supervised lockout valves with a safety device to relieve excess pressure.
5.4.1.2 Pipe or tube shall meet or exceed one of the standards
evacuation from and prevent entry into hazardous atmospheres 5.3.6 A reliable means shall be provided to indicate the pres- in Table 5.4. 1.2, except as permitted by 5.4.1.3 or 5.4.1.4.
4.4 Qualifications. Hybrid systems shall be designed, in-
and also to provide means for prompt rescue of any trapped sure in all storage containers that will be pressurized.
stalled, serviced, and mainL:1.ined by personnel that are trained
personnel. Safety items such as personnel training, warning 5.4.1.3 Pipe used exclusively to flow inert gas agent shall be
and certified for the service performed by the manufacturer or
signs, discharge alarms, self-contained breathing apparatus 5.3. 7 Water tanks shall be further supervised for the following permitted to be black steel, in accordance with ASTM A53/
an organization acceptable to the authority having jurisdiction.
(SCBA), evacuation plans, and fire drills shall be considered. conditions: A53M or Al06/Al06M.
4.2.3 In the event of a system discharge, unprotected person- (I) Water level 5.4.1.4 Where the pipe or tube identified in Table 5.4.1.2 or
Chapter 5 Components (2) Water temperature (for tanks located in unheated areas)
nel shall not enter the space until it has been ventilated and it 5.4.l.3 is not suitable for the environmental conditions, other
is determined that the atmosphere is safe for unprotected 5.3.8 A reliable means shall be provided to visually indicate pipe materials that are manufactured to ASTM standards shall
5.1 Water Supply.
personnel to enter. the level in all water storage containers. be permitted where the pipe or Lube is investigated for compat-
5.1.1* Quality. The water supply for a hybrid system shall be ibility with the system and the environment.
4.2.4 Before system cylinders are handled or moved, the 5.3.9 Each storage container shall have a permanent name-
taken from a source that is equivalent in quality to a potable
following steps shall be taken: plate or other pennanent marking that indicates the following: 5.4.2 Pressure Rating Design Requirements.
source with respect to particulate and dissolved solids.
(1) Cylinder outlets shall be fitted with anti-recoil devices, (1) For inert gas agent containers, the agent, pressurization 5.4.2.1 * Each piping network shall be designed to the maxi-
cylinder caps, or both whenever the cylinder outlet is not 5.1.2* Filters and Strainers for Nozzles. A filter or strainer
level of the container, and nominal agent volume at mu!D pressure and temperature to which it could be su~jected
connected to the system pipe inlet. shall be provided at the supply side of each nozzle, unless
standard temperature and pressure (STP) within the system listing parameters.
(2) Actuators shall be disabled or removed before cylinders permitted to be omitted by the authority havingjurisdiction.
(2) For water containers, pressurization level of the container
are removed from retaining bracketing. 5.4.2.2 The minimum design pressure for piping downstream
5.1.3 Filters and Strainers for Water Supply Connections. and nominal water volume
of a pressure-reducing device shall be determined from the
4.2.4.1 Safe handling procedures shall be followed when 5.1.3.1 * A filter or a strainer shall be provided at each water maximum anticipated pressure in the downstream piping as
transporting system cylinders. supply connection. predicted by system flow calculations.
4.2.4.2 Equipment designed for transporting cylinders shall 5.1.3.2 Strainers shall be provided with a cleanout port.
be used. "When dollies or carts are used, cylinders shall be
secured. 5.1.3.3 Strainers shall be accessible. Table 5.4.1.2 Pipe or Tube Standards

4.2.4.3 The system manufacturer's service procedures shall be 5.1.4 Filter Rating or Strainer Mesh Openings. The maximum
filter rating or strainer mesh opening shall not be greater than Materials and Dimensions and Stanq.ard Titles Standard No.
followed for specific details on system operation, maintenance,
and safety considerations. 80 percent of the minimum nozzle waterway dimension. Copper Tube (Drawn, Seamless)
5.2* Inert Gas Agent Supply. The inert gas agent supply shall Standard Specification for Seamless Copper TubrI" ASTM B75/B75M
4.3 Use Restrictions
be at least 99.9 percent pure with a water content Standard Specification for Seamless Copper Water TubrI" ASTMB88
4.3.1 Normally Occupied Areas. Hybrid systems shall be <0.005 percent. Standard Specification for General Requirements for Wrought Seamless Copper and Copper-Alloy Tube ASTM B251/B251M
permitted in normally occupied areas only where one of the Stainless Steel
following conditions is applicable: 5.3 Storage Containers. Standard Specification for Seamless and Welded Auslenitic Stainless Steel Tubing for General Service ASTM A269 / A269M
(1) Where exposure times to sea level equivalent oxygen 5.3.1 The inert gas agent and.water storage containers shall be Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing (Small-Dillmeter) for ASTMA632
concentrations above 12 percent can be limited to permitted to be cylinders, tubfs, or fabricated tanks. ·ceneral Service
5 minutes Standard Specification for Welded, Unannealed Austenitic Sta·inless Steel Titbular Products ASTM A778/A778M
(2) Where exposure times to sea level equivalent oxygen 5.3.1.1 Storage containers shall be manufactured from a mate- Standard Specification for Seamless and Welded Ferrilic/A ustenitic Stainless Steel Tubing for General Service ASTM A789/A789M
concentrations above 10 percent can be limited to rial or provided with an interior coating that is compatible with Standard Speczficatwn for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes ASTM A312/A312M
3 minutes the material being stored. Galvanized Steel Pipe
Standard Specification fur Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless ASTM A53/ A53M
4.3.2 Normally Unoccupied Areas. Hybrid systems with sea
Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service ASTM Al06/ Al 06M
level equivalent oxygen concentrations above 8 percent shall be
*Denotes tube smtablc for bending (see 12. 5. 7) according to ASTM standards.

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 770-10 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS COMPONENTS 770-11

5.4.3 Pressure Relief. 5.4_7 Valves_ 5.5.3 The hybrid nozzle shall produce 1;v'ater droplets with a 5.6.6.5.3 v\lhere mechanical system actuation is possible, a
Dv0 _9\! of 200 µm (0.0079 in.) at the minimum nozzle operating discharge pressure switch or a flow switch shall provide an
5.4.3.1 * A listed pressure relief device shall be installed in the 5.4.7.1 All valves shall be listed or approved for the intended alarm-initiating signal to the releasing panel.
pressure.
sections of pipe where the pressure could exceed the maxi- use.
mum allowable working pressure. 5.5.4 Where corrosive conditions are known to exist, 5.6.6.5.4 A means of manual release shall not be required for
5.4.7.2 For flanged valves, the class and style of flanges corrosion-resistant materials or coatings applied by the manu- automatic systems when the hazard being protected is u-noccu-
5.4.3.2 The pressure relief device shall operate at a pressure required to match the valve's flanged connection shall be used. piable, and the hazard is in a remote location where personnel
facturer shall be required to protect the nozzle.
not exceeding the maximum allowable working pressure.
5.4.7.3 Valves shall be protected agamst mechanical, chemical, are not nonnally present.
5.5.5 Hybrid nozzles shall be permanently marked to identify
5.4.4 Pipe Requirements. or other damage.
the manufacturer as well as the type and size of the orifices. 5.6.6.5.4.1 The normal manual control(s) for actuation shall
5.4.4.1 Wherever the word pipe is used, it shall be understood 5.4. 7.4 Special corrosion-resistant materials or coatings shall be located for easy accessibility at all times, including at the
5.6 Detection, Actuation, Alarm, and Control Systems. time of a fire.
also to mean tube. be used in corrosive atmospheres.
5.6.1 Detection, actuation, alarm, and control systems shall be 5.6.6.5.4.2 The manual control(s) shall he of distinct appear-
5.4.4.2 Pipe shall be of material having physical and chemical 5.4.7.5 Where directional valves are used for multihazard
installed, tested, and maintained in accordance with NFPA 72 ance and clearly recognizable for the purpose intended.
characteristics such that its integrity under stress can be predic- protection, the directional valves shall be listed or approved for
and NFPA 70.
ted with reliability. the intended purpose. 5.6.6.5.4.3 All manual operating devices shall be identified as
5.6.2 Automatic detection and actuation shall be used. to the hazard they protect.
5.4.4.2.1 Pipe shall have minimum working pressure ratings 5.4. 7 .6 Where directional valves are used for multihazard
based on the maximum operating pressure of the system. protection, the control equipment shall be specifically listed for 5.6.3 Actuation by only manual means shall be permitted if 5.6.6.5.4.4 Operation of any manual control shall cause the
the number, type, and operation of those valves. acceptable to the authority having jurisdiction. complete system including any required auxiliary functions to
5.4.4.2.2* The thickness of the piping shall be calculated
using the formula given in ASME B31.1. 5.4.8 Lockout Valve. A manually operated lockout valve shall 5.6.4 Adequate and reliable primary and 24-hour minimum operate as designed.
be provided on all systems to prevent the flow of inert gas agent standby sources of energy shall be used to provide for opera- 5.6.7 Electric Actuator Supervision.
5.4.5 Fittings and Piping Connections.
and water to the discharge device(s) during maintenance of tion of the detection, signaling, control, and actuation require-
5.4.5.1 Fittings shall conform to ASME B31.l or an equivalent the system. ment<; of the system. 5.6.7.1 Removal of an electric actuator from the agent storage
standard and be of material having physical and chemical char- container discharge valve that it controls sha11 result in an audi-
5.4.8.1 The lockout valve shall be located in accordance with 5.6.5 Automatic Detection. ble and visual indication of system impairment at the system
acteristics such that its integrity under stress can be predicted the manufacturer's instructions.
with reliability. 5.6.5.1 Automatic detection shall be by any listed method or releasing control panel.
5.4.8.2 The lockout valve shall provide a supervisory signal device capable of detecting and indicating heat, flame, smoke, 5.6. 7.2 Removal of an electric actuator from the selector valve
5.4.5.2 The fittings shall have corrosion resistance equal to the
when it is not in the open position. combustible vapors, or an abnormal condition in the hazard, it controls shall result in an audible and visual indication of
connected piping.
such as process trouble, that is likely to produce fire. system impairment at the system releasing control panel.
5.4_9 Drain-
5.4.5.3 Fitting materials shall be compatible with the connec-
5.6.5.2 Where a new hybrid system is being installed in a space 5.6.8 Operating Alarms and Indicators.
ted pipe to prevent galvanic Corrosion at the connection joint. 5.4.9.1 A low-point drain shall be provided in the water
that ha<; an existing detection system, an analysis shall be made
discharge pipeline to permit draining any residual water from 5.6.8.1 Alarms or indicators or both shall be used to indicate
5.4.5.4 Fittings shall have a minimum rated working pressure of the detection devices to ensure that the detection system is
the pipeline. the operation of the system, hazards to personnel, or failure of
equal to or greater than the maximum system operating pres- in good operating condition, will respond promptly to a fire
sure or as otherwise listed or approved. 5.4.9.2 Where multiple low points in a water discharge piping situation, and is compatible with the releasing service fire any supervised device.
network occur, a drain shall be provided at each occurrence. alarm control unit.
5.4.5.5 Cast-iron fittings shall not be used. 5.6.8.1.1 The type (audible, visual, or olfactory), number, and
5.4.9.3 Each drain valve shall either provide a supervisory 5.6.6 Operating Devices. location of the devices shall be such that their purpose is satis-
5.4.5.6 All threads used in joints and fittings shall conform to factorily accomplished.
signal when it is not in the closed position or be lockable in the 5.6.6.l Operating devices shall include agent-releasing devices
ASME B1.20.1 or ISO 7-1.
closed position. or valves, discharge controls, and shutdown equipment neces- 5.6.8.1.2 The extent and type of alarms or indicator equip-
5.4.5. 7 Welding and brazing alloys shall have a melting point sary for successful performance of the system. ment or both shall be approved.
5.4.10 Identification of Valves.
above 538°G (I000°F).
5.4.10.1 All control, drain, and test connection valves shall be 5.6.6.2 Operation shall be by a listed mechanical, electrical, or 5.6.8.2* Audible and visual predischarge alarms shall be pro-
5.4.5.8 Where copper, stainless steel, or other suitable tubing pneumatic means with an adequate and reliable source of vided within the protected area of normally occupied or occu-
provided -with pennanently marked, weatherproof, metal or
is joined with compression-type fittings, the manufacturer's energy. piable spaces to give positive warning of impending discharge.
rigid plastic identification signs.
pressure and temperature ratings of the fitting shall not be
exceeded. 5.4.10.2 The sign shall be secured with corrosion-resistant 5.6.6.3 All devices shall be designed for the service they will 5.6.8.2.1 The time delay shall be sufficient to allow personnel
wire, chain, or other approved means. encounter and shall not readily be rendered inoperative or evacuation prior to discharge.
5.4.5.9 Where copper tubing is joined by soldering, the join- susceptible to accidental operation.
ing material used shall be adequate for the system listing 5.4.11 Pipe Hangers/Supports. 5.6.8.2.2 The operation of the notification appliances shall be
temperature and piping network maximum pressure. 5.6.6.4 All devices shall be located, installed, or suitably continued after hybrid media discharge, until the alarm has
5.4.11.1 All references to hangers shall indude supports. protected so that they are not subject to mechanical, chemical, been acknowledged and appropriate actions have been taken.
5.4.5.10 Grooved fittings shall be permitted provided they are or other damage that would render them inoperative.
listed for the pressure and temperature requirements and meet 5.4.11.2* -Hangers shall be installed throughout the piping 5.6.8.2.3 For hazard area<; subject to fast growth fires, where
the corrosion resistance requirements of the piping network. netw"ork to prevent excessive bending and shear stresses in 5.6.6.5 A means of manual release of the system shall be pro- the provision of a predischarge alarm and time delay would
both the horizontal and vertical axes during _system discharge. vided. seriously increase the threat to life and property, the predis-
5.4.6 Strainers or Filters. charge alarm and time delay shall be permitted to be elimina-
5.5 Hybrid Nozzles. 5.6.6.5.1 Manual release shall be accomplished by a mechani-
5.4.6.1 Strainers or filters shall be installed in the water distri- ted.
5.5.1 Hybrid nozzles shall b~,listed for the intended use. cal manual release or by an electrical manual release when the
bution system per the manufacturer's listed design, installation, control equipment monitors the battery voltage level of the 5.6.8.3 Audible and visual alarms associated with the hybrid
and maintenance manual. 5.5.2 Listing criteria shall include flow characteristics, orienta- standby battery supply and provides a low-battery signal. system shall be distinct from all other alarms, including the
tion, area coverage, minimum and maximum spacing between building .fire alarm system.
5.4.6.2 Strainers and filters shall be listed or approved for the 5.6.6.5.2 The release shall cause simultaneous operation of
intended use. nozzles, height limits, droplet size distribution, and operating
automatically operated valves controlling agent release and 5.6.8.4* Abort switches shall be permitted only where
pressure.
distribution. approved by the authority having jurisdiction.

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 770-12 HYBRID (WATER AND INERT GAS) F1RE-EXTINGUISHING SYSTEMS APPLICATION AND FIRE TEST PROTOCOLS 770-13

5.6.8.4.1 Abort switches shall be located within the protected 5.6.9.8 Disconnect Switch. To avoid unwd.nted discharge of an 6.2.3 Application Parameters.
area, near the means of egress for the area. electrically actuated hybrid fire-extinguishing system, a super-
6.2.3.l Application parameters shall be the features that
vised disconnect switch shall be provided.
5.6.8.4.2 The abort switch shall be of a Lype that requires define an application.
constant manual pressure to cause abort. 5.6.9.8.1 The disconnect switch shall interrupt the releasing
6.2.3.2* Application parameters shall include enclosure varia-
circuit to the suppression system.
5.6.8.4.3 In all cases, the normal manual control and the bles, fire hazard properties, and occupancy status, with consid-
manual emergency control shall ovenide the abort function. An inert gas leak can reduce 5.6.9.8.2 The disconnect switch shall cause a supervisory eration for specific system performance objectives.
oxygen level in this area. signal at the releasing control unit.
5.6.8.4.4 Operation of the abort function shall result in both 6.2.4 Applicability. Fire test protocols shall be designed to
audible and distinct visual indication of system impairment. 5.6.9.8.3 The disconnect switch shall be secured against unau- replicate the range of the application parameters associated
Enter with caution.
thorized use by one of the following methods: with a particular hazard.
5.6.8.4.5 The abort switch shall be clearly recognizable for the
purpose intended. (1) Locate inside a lockable releasing control panel 6.2.5 Testing. Test protocols shall be conducted to verify the
(2) Locate inside a lockable enclosure working limits and installation parameters of the system and its
5.6.8.5 Alarms indicating failure of supervised devices or (3) Require a key for activation of the switch
FIGURE 5.6.8.6.2(c) Sign at Every Entrance to Inert Gas components, as described in the manufacturer's design and
equipment shall give prompt and positive indication of any fail-
Storage Rooms or Areas where Inert Gas Could Collect in the 5.6.9.8.4 When the disconnect switch requires a key for activa- installation manual.
ure and shall be distinctive from alarms indicating operation or
hazardous conditions. Event of a Discharge from a Safety Device or Control Panel tion, the access key shall not be removable while disconnected 6.2.6 Design, Installation, Operation, and Maintenance
Leak. so the suppression system can be quickly returned to the opera- Manual.
5.6.8.6 Warning and instruction signs at entrances to and tional condition in the event of a fire.
inside protected areas shall be provided. 6.2.6.1 The system design and installation manual evaluated
5.6.9.8.5 Suppression system disconnect achieved via software by the tests shall identify the working limil'> and parameters of
5.6.8.6.1 Warning signs shall be affixed in a conspicuous loca- programming shall not be acceptable for use in lieu of a physi- the system, the fire hazards, and the range of enclosure varia-
tion in every protected space; at every entrance to protected
spaces; at every remote manual actuation station; at every
entrance to inert gas storage rooms; and where inert gas might
•"' WARNING
I\, '
cal disconnect switch.
5.6.9.8.6 The disconnect switch shall be listed or be an inte-
bles, as applicable, consistent with the listing.
6.2.6.2 The system design and installation manual evaluated
collect and result in a reduced oxygen atmosphere in the event Hybrid media fire protection grated component of listed equipment. by the tests shall include design, installation, acceptance, test-
ofa discharge from a safety device or control panel leak. system reduces oxygen level ing, inspection, and maintenance procedures in accordance
when activated. Chapter 6 Application and Fire Test Protocols with the requirements of this standard and the manufacturer's
5.6.8.6.2 The safety sign format and color and the letter style
recommendations.
of the signal words shall be in accordance with ANSI Z535.2, as Before actuating, be sure
-Shown in Figure 5.6.8.6.2(a) through Figure 5.6.8.6.2(d). 6.1 * General. 6.3 Performance Objectives. The firefighting performance
personnel are clear of the
objective of a hybrid extinguishing system shall be to achieve
protected area. 6.1.1 Listing or Approval. Hybrid extinguishing systems shall
fire extinguishment with a duration of protection designed to
be designed and installed for the specific hazards and protec-
prevent reignition. (See 3.3.5, .Fire .l!.Xtinguishmenl.)
tion objectives identified in the listing or in accordance with
FIGURE 5.6.8.6.2(d) Sign at Every Remote Manual criteria approved by the authority having jurisdiction. 6.4 Application Parameters.
Actuation Station.
6.1.2 Application Characteristics. The enclosure variables, as 6.4.1 * Total Flooding Enclosure Variables. Enclosure varia-
applicable, and hazard classification of the specific application bles shall include the geometry of the enclosure, unclosable
5.6.9 Control Equipment. shall be consistent with the listing or in accordance with crite- opening(s), and the ventilation conditions in the enclosure.
ria approved by the authority having jurisdiction.
5.6.9.1 * The control equipment shall supervise the detection, 6.4.1.1 Enclosure Geometry. The enclosure geometry, as
Hybrid media fire protection manual controls, actuating devices, and associated wiring and, 6.1.3 Application Evaluations. An evaluation of the enclosure applicable, including floor area, volume, ceiling height, and
system reduces oxygen when activated, cause actuation of the system and operd.tion of geometry {as applicable), the fire hazards, and the system varia- aspect ratio, shaII be considered when designing such parame-
level when activated. any required auxiliary functions. bles described in this chapter shall be performed to ensure that ters as nozzle locations, system flow rate, and total hybrid
When alarm operates, the system design and installation are consistent with the listing media use needs of the system.
5.6.9.2 The control equipment shall be specifically listed for
or in accordance with criteria approved by the authority having
vacate immediately. compatibility with the number and 'type of actuating devices. 6.4.1.2 Ventilation. Ventilation considerations shaII include
jurisdiction.
5.6.9.3 All circuitry that is monitoring or controlling the both natural and forced ventilation parameters.
6.1.4 Pre-Engineered Systems. Pre-engineered hybrid extin-
hybrid fire-extinguishing system shall be electrically supervised 6.4.1.2.1 * Natural Ventilation.
FIGURE 5.6.8.6.2(a) Sign in Every Protected Space. guishing systems for total flooding applications shall not be
in accordance with NFPA 72.
extrapolated beyond the enclosure volume, ceiling height, 6.4.1.2.1.1 * The number, size, and location of the openings in
5.6.9.4 Sensors providing feedback for system operation shall ventilation rate, and number of nozzles tested, unless dimen-
the space shall be addressed in the design and installation of
be identified as such on the sensor or an adjacent surface. sions of the enclosure are such that additional nozzles are the system.
required to maintain nozzle spacing.
5.6.9.5 Conductors providing feedback for system operation 6.4.1.2.1.2* In some cases, special precautions shall be given
shall be in accordance with the manufacturer's specifications. 6.2* Listing or Approval Evaluations. to minimize the effects of openings in the space.
Hybrid media fire protection 5.6.9.6* "Where pneumatic control equipment is used, the 6.2.1 * General. Listing or ap·proval of hybrid extinguishing
6.4.1.2.2 Forced Ventilation.
system reduces oxygen level pneumatic lines shall be protected against crimping and systems shall be based on a comprehensive evaluation designed
when activated. mechanical damage. to include fire test protocols, system component test proce- 6.4.1.2.2.1 The magnitude of the forced ventilation in the
dures, and a review of the manufacturer's design, installation, enclosure shall be addressed in the design and installation of
When alarm operates, enter 5.6.9.7 "Where mechanical' system operation is possible, a operation, and mamtenance manual. the hybrid extmguishing system.
discharge pressure switch shall be instaIIed on the system
only with extreme caution 6.2.2* Fire Test Protocols. Fire test protocols shall be 6.4.1.2.2.2 In some cases, consideration shaII be given to shut-
piping to provide an alarm-initiating signal to the releasing
or after area is ventilated. designed to address performance objectives of the application ting down the forced ventilation prior to ~ybrid system activa-
panel.
specified in the listing or in accordance with criteria approved tion.
FIGURE 5.6.8.6.2(b) Sign at Every Entrance to Protected by the authority having jurisdiction and the application param-
Space. eters described in Section 6. 4.

2021 Edition 2021 Edition

 770-14 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS DESIGN REQUIREMENTS FOR TOTAL FLOODING SYSTEMS 770-15

6.4.2 Fire Hazard Classification. Fire hazards shall be classi- U) Fuel spray orientation 8.2 Enclosure Requirements. 8.4 Hybrid Media Quaotiiy.
fied as follows: (k) Reignition sources
8.2.1 Enclosure Strength and Pressure Relief. 8.4.1 The minimum quantity of inert gas agent required shall
(I) Specific total flooding application systems in accordance 6.4.2.2.4.5 When designing and installing hybrid fire extin- be calculated in accordance with the following equation:
with Chapter 8 and this section guishing systems to protect Class B hazards, the parameters 8.2.1.1 The protected enclosure shall have the structural
(2) Specific local application systems in accordance with specified in 6.4.2.2.4.4 shall be considered. strength and integrity necessary to contain the agent discharge.
Chapter 9 and this section [8.4.1]
6.4.2.2.5 Class C Fires. Electrical conductivity of water and 8.2.1.2 An estimate of the maximum positive pressure, relative
6.4.2.1 Combustible Loading. to ambient pressure, expected to develop upon discharge of
hybrid media shall be addressed when considering applications Qmin -F ·Vmr ·( 294.4 J·X·Faim
where the primary fire is a Class C fire. the agent shall be determined. - S,IC:
273 + T .
mm
6.4.2.1.1 A fire hazard analysis shall be conducted to deter-
mine both the, design parameters of the hybrid cxLinguishing 6.4.2.2.6 Combination Fires. Combinations in fuel loadings 8.2.1.3 If the developed pressures present a threat to the
system and the type of detection and activation scheme structural strength of the enclosure, additional venting shall be where:
and hazards shall be addressed.
employed by the system. provided to prevent excessive pressures. Q,,,;,, = minimum volume of inert gas agent to be added (m3 )
6.4.3 Fire Location. The location of the fuel in the space shall F.i·,1c = inert gas agent safety factor
6.4.2.1.2 The system shall be based on the fuel type, combusti- be considered when selecting and designing a hybrid fire extin- 8.2.1.4 Designers shall consult the system manufacturer's v;,,." = volume of the enclosure (m·~)
ble loading, and anticipated fire growth rate as well as the guishing system, including the following: recommended procedures relative to enclosure venting. 1: ,
11 11
= minimum expected ambient enclosure temperature
desired firefighting performance objectives. (OC)
(1) Fuel located at higher elevations in the space 8.2.2* Enclosure Integrity and Loss of Hybrid Media. The
6.4.2.2 Fuel Type. (2) Fuel located in close proximity to vent openings concentration of hybrid media shall be maintained for the X = flooding factor at 21 °C ambient temperature (m 3/m 3 )
(3) Fuel located in the corners of the space specified duration of protection. (See Section 8. 6.) Faim = atmospheric correction factor
6.4.2.2.1 Fire Hazard Classification. The fire hazard classifica-
(4) Fuel stacked against walls 8.4.1.1 The inert gas agent safety facLor, 1'~,1c, shall be 1.2.
tion shall be directly related to the type and quantity of the fuel 8.2.3 Forced-Air Ventilation Systems and Loss of Hybrid
present in a space. 6.4.4 Obstructions and Shielding. Media.
8.4.1.2* The flooding factor, .x; shall be determined by test for
6.4.2.2.2 Fire Hazard Characteristics. The ease of ignition 6.4.4.1 Hybrid media nozzles shall be positioned to distribute 8.2.3.1 * Forced-air ventilation systems shall be shut down or the specific fuel or hazard type, per Section 8.3.
and reignition of the fuel, the fire growth rate, and the diffi- hybrid media to all locations in the area or around the object closed automatically where their continued operation would
adversely affect the performance of the fire-extinguishing 8.4.1.3 The design quantity of the inert gas agent shall be
culty of achieving extinguishment shall be considered when being protected.
system or result in propagation of the fire. adjusted in accordance with Table 8.4.1.3 to compensate for
selecting or designing a hybrid extinguishing system.
6.4.4.2 The presence of obstructions and the potential for ambient pressures that vary more than 11 percent [equivalent
6.4.2.2.3 Class A Fires. shielding of spray patterns shall be evaluated to ensure that the 8.2.3.2 The volume of a recirculating ventilation system and to approximately 915 m (3000 ft) of elevation change] from
system performance is not affected. associated ductwork shall be considered part of the total hazard standard sea level pressures [760 mm Hg at 0°C (29.92 in. Hg
6.4.2.2.3.1 Fuel loading and configuration shall be considered volume when determining the quantity of hybrid media. at 70°F)].
when selecting and designing a system to protect a space or 6.5 Flooding Factor. The flooding factor, X, as used in the
area containing Class A materials. equation in 8.4.1, shall be determined for the specific fuel by 8.2.3.3 Where a non-recirculating ventilation system is not
testing in accordance with Section 8.3. shut down, additional hybrid media shall be introduced to Table 8.4.1.3 Atmospheric Correction Factors, Fatm
6.4.2.2.3.2 Consideration shall be given to the potential for maintain the required design application density.
deep-seated fires as well as to the potential for smoldering fires. Enclosure Pressure
Chapter 7 System Design Requirements 8.3 System Performance Characteristics. Atmospheric
6.4.2.2.4 Class B Fires. Equivalent Altitude (Absolute)
Correction
8.3.1 Protection of Class A, Class B, and Class C Hazards.
6.4.2.2.4.1 The hazard(s) associated with Class B fires shall be 7.1 General. Hybrid extinguishing systems shall be designed ft km psi mmHg Factor
The following characteristics of the system shall be determined
related primarily to the fuel loading, fuel configuration, flash- and installed for the specific hazards and protection objectives
for a given fuel or hazard type by performance-based testing or -3,000 -0.92 16.25 840 l.11
point, and burning rate of the fuel. specified in the listing or in accordance with criteria approved
listing: -2,000 -0.61 15.71 812 1.07
by the authority having jurisdiction.
6.4.2.2.4.2 Preburn time, which affects the overall characteris- (I) Inert gas agent discharge rate of the hybrid nozzle, Rv,1c; -1,000 -0.30 15.23 787 1.04
tics of the fire, shall be evaluated. 7 .2 Pipe Network Layout and Design. (2) Water discharge rate of the hybrid nozzle, Rn,no 0 0.00 14.70 760 1.00
(3) Intended dry-basis concentration of oxygell at 21 °C 1.000 0.30 14.18 733 0.96
6.4.2.2.4.3 Class B fires shall be grouped into the following 7.2.1 Pipe shall be sized for the intended system flow rates in
(70°F) ambient temperature, C ,..ygen 2,000 0.61 13.64 705 0.93
categories: accordance with the manufacturer's manual. 0

(4}* Time to extinguishment 3,000 0.91 13.12 678 0.89

(1) Two-dimensional pool fires 7.2.2 Fixtures and connections shall be provided to facilitate (5) Maximum time to discharge the minimum volume of 4,000 1.22 12.58 650 0.86
(2) Three-dimensional spray and running fuel fires system testing in accordance -with Chapters 12, 13, and 14. inert gas agent, ln 5,000 1.52 12.04 622 0.82
(6) Maximum protected volume per hybrid nozzle 6,000 1.83 11.53 596 0.78
6.4.2.2.4.4 The parameters associated with each Class B cate-
(7) Maximum ceiling height 7,000 2.13 11.03 570 0.75
gory shall be as follows: Chapter 8 Design Requirements for Total Flooding Systems
(8) Maximum coverage area dimensions (width x length) 8.000 2.45 10.64 550 0.72
(1) Class B two-dimensional fires, as follows: per hybrid nozzle 9,000 2.74 10.22 528 0.69
8.1 General.
(a) Fuel loading and configuration (9) Minimum clearance to walls 10,000 3.05 9.77 505 0.66
(b) Fuel flashpoint 8.1.1 Description. A total flooding system shall consist of a (10) Minimum and maximum clearance to ceiling
(c) Preburn time pool/spill size fixed supply of hybrid media permanently connected to a fixed
8.3.2 Protection of Mixed Hazards. For combinations of fuel
(2) Class B three-dimensional fires, as follows: pipe network with fixed nozzles arranged to discharge the
or hazard types, the system design characteristics shall be deter-
hybrid media into an enclosed space or an enclosure about the
(a) Fuel loading and configuration mined by the fuel or hazard type that requires the most restric-
hazard.
(b) Fuel flashpoint tive design parameters, unless tests are performed on the
(c) Preburn time 8.1.2 Uses. A total flooding system shall be used where there actual combination of fuel or hazard types.
( d) Cascade/running fuel fires is a permanent enclosure around the hazard that enables the
(e) Fuel flow rate required density of hybrid media to be discharged for extin-
(f) Fire configuration guishment and prevent fire re-ignition for the required period
(g) Spray fires of time or for a time period sufficient to allow for response by
(h) Fuel line pressure trained personnel.
(i) Fuel spray angle

2021 Edition 2021 Edition

 770-16 HYBRJD (WATER AND INERT GAS) FIRE-EXTINGUJSI-IING SYSTEMS DESIGN REQUIREMENTS FOR LOCAL APPLICATION SYSTEMS 770-!7

8.4.2 The system discharge rate shall be calculated in accord- t = design discharge duration (min) Chapter 9 Design Requirement<, for Local Application 9.2.3 Flammable Liquid Hazards. Where flammable liquids
ance with the following equation: Systems with depth greater than 6 mm (¼ in.) are to be protected, a
8.4.5.1 The water safety factor, 1<;,11, 0 , shall be 1.2.
minimum frceboard of 30 mm (1.2 in.) shall be provided,
8.4.5.2 The design discharge duration, t, shall be determined 9.1 General. unless other.vise noted in the nozzle listing or as approved by
[8.4.2]
from the supplied' quantity of inert gas agent, Q,.,pp1_,, and the the authority having jurisdiction.
9.1.1 Description. A local application system shall consist of a
actual system discharge rate. fixed supply of hybrid media permanently connected to a fixed 9.3 Nozzle Selection, Quantity, and Location.
8.4.6 The supplied quantity of hybrid media shall be increased pipe nehvork with fixed nozzles arranged to discharge the
hybrid media on or around the hazard or object to be protec- 9.3.1 The basis for nozzle selection shall be performance data
where: through the use of additional design factors to compensate for that clearly depict the interrelationship of agent quantity,
any special conditions that would affect the extinguishing effi- ted.
R,ys,min = minimum total system discharge rate (m·~/min) discharge rate, discharge time, area coverage, orientation, and
Q.";n = minimum volume of inert gas agent (m 3 ) ciency. 9.1.2 Uses. A local application system shall be used to protect the horizontal and vertical distance of the nozzle from the
ln = maximum _time to discharge Q.min (min) 8.5 Concentration of Oxygen. an object or a hazard in an unenclosed or partially enclosed protected surface.
condition.
8.4.2.1 * The maximum time, tv, to discharge the minimum 8.5.1 The resultant concentration of oxygen shall be calcula- 9.3.2* The performance data required by 9.3.l shall be deter-
volume of inert gas agent shall not exceed 3 minutes, unless a ted using the following equation: 9.1.3 General Requirement<,. Local application systems shall mined by fire testing that is representative of the configuration
longer time is established by test for a specific hazard. be designed, installed, tested, and maintained in accordance and conditions of the hazard being protected.
with the applicable requirements in Chapter 4 and with the
8.4.2.2 "Where multiple hazard classifications exist in the [8.5.1] additional requirements set forth in Chapter 13. 9.3.3 The number of nozzles required to cover the entire
protected enclosure, the shortest time to discharge, tv, shall be hazard area shall be based on the area coverage of each nozzle.
used. 9.1.4 Application Characteristics. The characteristics of the
local application shall be consistent ,vith the listing of the 9.3.4 Local application nozzles shall be located in accordance
8.4.3* The number of hybrid nozzles shall be determined in system or approved by the authority having jurisdiction. with spacing and discharge rate limitations stated in nozzle list-
accordance with the following equation: where: ings or approved by the authority having jurisdiction.
C"·'<J'K""·"'1 = concentration of oxygen after discharge (%vol/vol) 9.1.5 Safety Requirements. The safety requirements of
Section 4.2 shall apply where locally high concentrations of the 9.3.5 Nozzles shall be located so as to protect coated stock or
7~nax = maximum expected ambient enclosure temperature other hazards extending above a protected surface.
[8.4.3] (OC) inert gas will be developed.
Q,u1,p1J, = discharged volume of inert gas agent (m3 ) 9.2 Hazard Specifications. 9.4 Discharge Rate.
F;,1m = atmospheric correction factor (See 8.4.1.3.) 9.4.1 The design discharge rate through individual nozzles
Vrnr = volume of the enclosure (m 3 ) 9.2.1 Extent of Hazard.
shall be determined on the basis of location or projection
where: 9.2.1.1 The entire hazard shall be protected. distance in accordance with specific listings or be approved by
8.5.2 The concentration of oxygen after discharge shall not be
N = minimum number of hybrid nozzles (nozzles) less than the thresholds specified in Section 4.3. the authority havingjurisdiction.
3 9.2.1.2 The hazard shall include combustible objects, hazards
R,ys,min = minimum system inert gas agent discharge rate (m /
which could cause spray fires, or all areas that are or can 9.4.2 The system discharge rate shall be the sum of the indi-
min) 8.6 Hybrid Media Retention for Prevention of Re-ignition.
become coated by combustible liquids or shallow solid coat- vidual rates of all the nozzles and discharge devices used in the
Rv,1c = inert gas agent discharge rate of the hybrid nozzle
8.6.1 * For fires involving Class A combustibles subject to deep- ings, such as areas subject to spillage, leakage, dripping, splash- system.
(m 3 /min/nozzle)
seated burning, an extinguishing atmosphere shall be main- ing, or condensation.
tained throughout Lhe hazard zone for a time period sufficient 9.5 Discharge Time.
8.4.3.1 The calculated number of hybrid nozzles shall be
9.2.1.3 The hazard shall also include all associated materials
rounded up to a whole number. to allow for response by personnel trained and equipped to 9.5.1 The design discharge time shall be not less than the
extinguish the fire. or equipment, such as freshly coated stock, drain boards,
hoods, ducts, and so forth, which could extend fire outside or greater of the following:
8.4.3.2 The spacing of hybrid nozzles shall not exceed the
manufacturer's specifications. 8.6.2 For hazards where there are objects that ·might be lead fire into the protected area. (I) 120 seconds
heated above ignition temperature of the fuel or where the (2) . Twice the extinguishment time as determined in accord-
8.4.4 The supplied quantity of inert gas agent, Qwf,ply• shall be 9.2.1.4 The hazard shall be so isolated from other hazards or
ignition te·mperature of a flammable liquid fuel is below the ance with Section 9.3
not less than the minimum, as determined in 8.4.1. combustibles that fire will not spread outside the protected
boiling point of the fuel, the hybrid media concentration shall
area. 9.5.2* The discharge time shall be increased to compensate
be maintained for a sufficient time to allow cooling below the
8.4.5 The supplied quantity of water shall be calculated from for any hazard condition that would require a longer cooling
the folluwing equation: fuel's ignition temperature or for response by personnel. 9.2.1.5 Curbing or dikes to isolate flammable liquid spills shall
period or for mechanical rundown time to prevent re-ignition.
be required to limit the spread of spi11s to the area protected by
8.7 Hybrid Nozzle Selection, Quantity, and Location.
the hybrid local application system. 9.5.3 v\i'here there is a possibility that metal or other material
[8.4.5] 8.7.1 Hybrid nozzles shall be selected, located, and oriented can become heated above the ignfrion temperature of the fuel,
9.2.1.6 Adjacent or interconnected hazards shall be permitted
in accordance -with the criteria determined in accordance with the discharge time shall be increased to allow adequate cooling
to be subdivided into smaller groups or sections with the
8.3.1. time.
approval of the authority havingjurisdiction.
where: 8.7.2 Discharge of inert gas agent and water shall be estab- 9.5.4* v\lhere the fuel has an autoignition point below its boil-
9.2.1. 7 Systems for the protection of hazards that are sub--
W = quantity of water (L) lished at every hybrid nozzle in 30 seconds or less from the ing point, such as paraffin wax and cooking oils, the discharge
divided in accordance with 9.2.1.6 shall be designed to give
r;,H,o = water safety factor time of system activation, unless a longer delivery time is
immediate independent protection to adjacent groups or
time shall be increased to permit cooling of the fuel to prevent
Yp;pe = internal volume of the water-filled pipe (L) permitted by the authority having jurisdiction. re-ignition.
sections.
N = minimum number of hybrid nozzles (nozzles) 8.7.3 Nozzles shall be placed such that their discharge will not 9.6 Hybrid Media Quantity. The quantity of hybrid media
Rv,H,o = water discharge rate of the hybrid nozzle (L/min/ 9.2.2 Location of Hazard.
splash flammable liquids or' create dust clouds that could required for local application systems shall be based on the rate
- nozzle)
extend the fire, create an' explosion, or otherwise adversely 9.2.2.1 The hazard shall be indoors. of discharge and the time that the discharge must be main-
affect the contents or the integrity of the enclosure. tained to ensure complete extinguishment.
9.2.2.2 The hybrid system shall be designed to account for air
movement and the ambient temperature range of the protec-
ted hazard.

2021 Edition 2021 Edition

770-18 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS INSTALLATION REQUIREMENTS 770-19

Chapter 10 Design Requirements for Marine Systems (22) Plan view of the protected area, showing enclosure parti- ( 4) Name of owner and occupant (13) Plan identification number or prqject number of the
(Reserved) tions (full and partial height); piping layout, in duding (5) Property location, including street address and site eleva- submitted as-built plans
identification of pipe type, contents, and size; nozzles; tion relative to sea level
pipe hangers and rigid pipe supports; seismic bracing, if (6) Description of occupancies and hazards (fuels) being
Chapter 11 System Documentation required; system actuation and control equipment; and protected Chapter 12 Installation Requirements
signage (7) Type of application, total flooding or local application
11.1 System Working Plans. (23) Plan v.iew of the protected area, in accordance with (8) System design requirements, induding the following: 12.1 General.
NfPA 70 and NFPA 72, showing detection, alarm, and 12.1.1 Listed materials and devices shall be installed in accord-
11.1.1 Submittal of Working Plans. Working plans shall be (a) Total flooding, design volume of space protected
control system, including all devices; end-of-line device ance with their listing.
submitted for approval to the authority having jurisdiction (b) Local application area of water application
locations; location of controlled/interlocked devices,
before any equipment is installed. (c) Total gas requirement
such a'> dampers/shutters, power supply equipment, fuel 12.1.2 Materials and devices shall be installed in accordance
(d) Total water requirement with the manufacturer's instructions.
11.1.2 Deviations from Approved Plans. Deviation from supplies, and air handling equipment
approved plans shall be approved by the authority having juris- (24) Isometric view of the hybrid distribution system, showing 11.2.4 Detailed Work Sheets. The calculation detailed -work 12.1.3 System components shall be located, installed, or
diction. detailed descriptions of each pipe segment; pipe fitting, sheets shall contain the following information:
protected so they are not subject Lo mechanical, corrosive
including reducers and strainers; control or selector
11.1.3 Qualifications. The working plans shall be prepared (1) Sheet number (chemical, etc.), or other damage that could impair operation.
valve; drain valve; and nozzle
by, or under the supervision of, an individual that 1s trained (2) Nozzle description
(25) Seismic separations and expansion joints, if any 12.1.4 Working Plans.
and certified by the system manufacturer. (3) Pipe size
(26) Calculation of seismic loads, if seismic restraint is
( 4) Pipe lengths, center to center of fittings 12.1.4.1 The system shall be installed in accordance with the
11.1.4 Component Identification. Special symbols shall be required
(5) Equivalent pipe lengths for fittings and devices approved working plans.
defined and used to clearly identify the components of the (27) Details of hangers, rigid pipe supports, and bracing
(6) Calculated nozzle pressure
hybrid system. (28) Details of container mounting, induding method of 12.1.4.2 Deviations from the approved working plans shall be
(7) Maximum calculated pressure in the pipe network
securing to building structure approved.
(8) Calculated flow rates:
11.1.5 Required Information. The working plans shall (29) System sequence of operations, including a complete
provide the following information as pertaining to the design step-by-step description of the functioning of abort and (a) Inert gas flow: slpm (scfm) 12.1.5 Qualifications. Hybrid systems shall be installed by
of the system: maintenance switches, delay timers, and any interlocks (b) Water flow: 1pm (gpm) personnel that are qualified in accordance with Section 4.4.
with HVAC equipment, dampers, production equip- (9) Calculated discharge time
(1) Plan identification number or project number 12.2 Nozzles. Nozzles shall be installed in accordance with
ment, fuel shutoffs, electric shut-downs, and door closers
(2) Name and address of plans preparer and installing 11.3 Detection, Actuation, and Control Systems Docwnenta- the manufacturer's instructions, including, but not limited to,
(30) Riser diagram of the system control panel
contractor tion. Documentation for detection, actuation, and control the following installation criteria:
(3) Hybrid extinguishing system manufacturer and system (31) Hydraulic and pneumatic calculations to determine flow
systems shall meet the requirements of NFPA 72.
rates, nozzle pressures, and maximum predicted pres- (1) Minimum and maximum height above the floor
designation
sure for each pipe network 11.4* Owner's Documentation. (2) Minimum and maximum distances between nozzles
(4) Date of preparation and subsequent revisions
(32) Calculations to determine the quantity of water, quantity (3) Minimum and maximum distance from nozzles to walls
(5) Nameofownerandoccupant 11.4.1 A copy of the manufacturer's design, installation, oper-
of inert gas agent, and discharge time or partitions
(6) Property location, induding street address and site eleva- ation, and maintenance manual(s) shall be provided to the
(33) Calculations to determine the size of backup batteries (4) Location of nozzles with respect to continuous or discon-
tion relative to sea level mvner.
(See NFPA 72.for documentation requirements.) tinuous obstructions
(7) Point of compass, drawing scale, and symbol legend
(34) Details of any special features 11.4.2 A copy of the as-built plans shall be provided to the (5) Clearance between the nozzle and the ceiling·
(8) Plan v.iew of the protected endosure or equipment
owner. (6) Permitted nozzle orientation
(9) Location and dimensions of obstructions that affect the 11.1.6 As-Built Plans. If the final installation varies from the
system layout approved working plans, new working plans, representing the 12.3 Hazardous Locations. Components of the electrical
11.4.3 An as-built instruction and maintenance manual that
(10) Location of fire walls that affect the system layout as-built installation, shaJI be prepared. portions of hybrid systems that are installed in classified loca-
indudes a full sequence of operations and a full set of drawings
(11) Endosure cross section, with full height or schematic tions as defined in Article 500 of NFPA 70 shall be listed for
11.2 System Flow Documentation. and calculations shall be maintained or be accessible on site.
diagram, induding location and construction of build- such use.
ing floor/ceiling assemblies above and below, raised 11.2.1 Pre-Engineered Systems. System flow calculations shall 11.5 System Information Sign.
access floor, and suspended ceiling 12.4 Electrical Clearances. All system components shall be
not be required for pre-engineered systems. 11.5.1* The installing contractor shall prov.idea permanently located so as to maintain minimum electrical clearances from
(12) Description of occupancies and hazards (fuels) being
protected 11.2.2 Engineered Systems. marked system information sign. live parts in accordance with Subpart S of 29 CFR 1910.
(13) Endosure occupancy status (normally occupied, occupi- 11.5.2 The sign shall be placed within 1.5 m (5 ft) of the stor- 12.5 Pipe Network.
able, or unoccupiable) 11.2.2.1 Pneumatic calculations for the inert gas agent
portion of the system shall be prepared on form shecL'> that age cylinders or releasing control panel.
( 14) Inert gas agent used in the hybrid media 12.5.1 Pipe Identification
include a summary and detailed work sheets. 11.5.3 The sign shall include the following information, as
(15)* Description of the critical system application criteria
applicable: 12.5.1.1 All pipe, induding specially listed pipe, shall be
(16) Maximum and minimum expected ambient tempera- 11.2.2.2 Hydraulic calculations for the water portion of the marked along its length by the manufacturer in such a way as
tures of the protected space and the agent storage system shall be prepared on form sheets that include a (I) Location of the protected area or areas to identify the type of pipe.
container location(s) summary and detailed work sheets. (2) Description of the hazard protected
(17) Location and description of the water and inert gas (3) Design type application 12.5.1.2 Pipe identification shall include the manufacturer's
agent supplies, including container quantity, capacity, 11.2.2.3 '1\There flow calculation software is used, flow calcula- name, model designation, and/or schedule.
(4) System manufacturer and system designation
weight, pressure, or other characteristics, as applicable tion details shall include the version of the flow calculation
(5) Volume or area protected, depending on application
(18) Identification of nozzles, including size and orifice or program. 12.5.1.3 Pipe or tubing marking shall not be painted,
(6) Total number of nozzles protecting the hazard
part number, as appropriate concealed, or removed prior to approval by the authority
11.2.3 Summary Sheets. The calculation summary sheet shall (7) Design application density
having jurisdiction.
(19) Identification of pipe and fittings, including material contain the following inform;tion: (8) Design flow rate and duration
specifications, grade, and pressure rating (9) Total inert gas agent and water requirements, as calcula- 12.5.1.4 Weldmg shall be performed in accordance with
(20) Description of wire or cable (1) Name and address of plans preparer and installing
ted Section IX, "Welding, Brazing, and Fusing Qualifications," of
(21) Equipment schedule or bill of materials for each piece contractor
(l 0) Description of any compartment or enclosure character- the ASME Boiler and Pressure Vessel Code.
of equipment or device, indicating the device name, (2) Hybrid extinguishing system manufacturer and system
istics that are essential to system performance
manufacturer, model or part number, quantity, and designation 12.5.2* Pipe shall be deaned internally and be free of foreign
_(11) Name of installing contractor and contact information
description (3) Date ofpreparntion ma~erial before nozzles are installed.
(12) Date of installation

2021 Edition 2021 Edition

 770-20 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS ACCEPTANCE TESTING 770-2I

12.5.3* If used, pipe joint compound, tape, or lubricant shall 12.5.8.5 'Where seismic bracing is required, bracing shall be in 12.8.4 All initiatmg and releasing circuit wiring shall be in- nent'i, the final testing shall be conducted with those systems as
be applied only to the male threads of the joint with the excep- accordance with local codes and the authority having jurisdic- stalled in conduit or closed raceway. appropriate.
tion of the first thread. tion.
12.9 System Review and Testing. The completed system shall 13.1.4 The completed system shall be reviewed and tested by
12.5.4 Installation Standards. 12.5.9 System Drainage. All system piping and fittings shall be be reviewed and tested by personnel qualified in accordance qualified personnel to meet the approval of the authority
installed so that the entire system can be drained. with Section 4.4 to determine that the system has been prop- having jurisdiction.
12.5.4.1 Where the maximum system operating pressure does
erly installed and will function as specified.
not exceed 12.1 bar (175 psi), piping and tubing shall be in- 12.5.10 Piping Slope Requirements. The wetted discharge 13.1.5 The completed system shall be reviewed to confirm that
stalled in accordance with NFPA 13. piping shall be installed with a slope of at least 2 mm/m (¼ in. 12.9.l Only listed or approved equipment and devices shall be only listed or approved equipment and devices have been used.
per 10 ft) of run toward the low point drain. used in the system.
12.5.4.2 v\lhere the maximum system operating pressure 13.1.6 The installing contractor shall take the following
exceeds 12.l bar (175 psi), piping and tubing shall be installed 12.6 Gas and Water Storage Containers. 12.9.2 Review of Installation. actions:
in accordance with ASME B31.1.
12.6.1 Accessibility. 12.9.2.1 It shall be determined that the protected enclosure is (1) Notify the authority having jurisdiction and the owner's
12.5.5 Pressure Rating. All system piping, tubing, and hose in general conformance with the construction documents'. representative of the time and date testing is to be
shall be rated for the maximum working pressure to which they 12.6.1.1 Storage containers and accessories shall be installed performed.
are exposed. so that inspection, testing, recharging, and other maintenance 12.9.2.2 All operating devices shall be checked for proper (2) Perform all required acceptance tests.
are facilitated. operation following directions to be given in the manufactur- (3) Confirm in writing the status of all system components
12.5.6 Flexible Components. Any flexible piping, tubing, er's installation operation and maintenance manual. and controls.
hose, or combination thereof shall be constructed and installed 12.6.1.2 A clear space, at least l m (3 ft) in front of the
containers, shall be marked to maintain access for mainte- (4) When the system has not been left in service, confirm in
in accordance with the manufacturer's instructions. 12.9.2.3 Proper operation of auxiliary devices such as pressure
nance. writing those responsible for placing the system in serv-
switches, flow alarms, and pressure trips shall be verified.
12.5.7* Tube Bending. ice.
12.6.2 Storage Temperatures. 12.9.2.4 Proper operation of all alarms and indicators shall be I
12.5.7.1 Bending of Type Kand Type L copper tube or stain- verified, 13.1.7 The acceptance testing shall be documenLed in a tesL
less steel tube shall be permitted, provided that all bending 12.6.2.1 Storage temperatures shall be maintained within the
range specified in the manufacturer's listing. 12.9.2.5 Proper operation of the fire alarm control panel and
report. I'
details are in accordance with the tubing manufacturer's 13.1.8 The acceptance test report shall be maintained by the
recommendations, the strength requirements of &'iME B31.1, all connected devices such as detectors, manual stations, time
12.6.2.2 External heating or cooling shall be an approved delays, alarms, remote annunciators and releasing devices shall system uwner for the life of the system.
or the following, whichever is greatest: method to keep the temperature of the storage container be verified. 13.2 Acceptance Requirements.
(1) For Type Kor Type L copper tubing, the minimum bend- within desired ranges.
ing radius is six pipe or tube diameters. 12.9.2.6* Sensors providing feedback for system operation 13.2.1 Review of Mechanical Components.
12.6.3 Container Securement. Containers shall be secured to shall be verified for proper connection to the system in accord-
(2) For Type 304L or Type 316 stainless steel tube, the mini-
prevent container movement and possible physical damage. ance with the manufacturer's instructions. 13.2.1.1 It shall be determined that the protected enclosure is
mum bending radius is two diameters up to 38 mm
(1 ½in.) OD and four diameters for 51 mm (2 in.) tubing. 12.6.4* Strainers and Filters. A strainer or filter shall be in general conformance with the construction documents.
12.9.2.7 All filters and strainers shall be inspected and cleaned
installed at each water supply connection. or replaced as necessary. 13.2.1.2 The piping system shall be inspected to determine
12.5.7.2 Bending tools shall be used for all bending in accord-
ance with the following: 12.7 Valves and Pressure Gauges. that it is in compliance with the design and installation docu-
12.9.3 Pressure Test of Pipe. ments and hydraulic calculations.
(1) Power bending tools with the correct radius dies shall be 12.7.1 Valves and pressure gauges shall be installed such that
required for tube larger than 20 mm(% in.). 12.9.3.1 The pipe system shall be pressure tested in a closed 13.2.1.3 Nozzles and pipe size shall be in accordance with the
they are accessible for operation, inspection, and maintenance. circuit using nitrogen or other dry gas.
(2) Hand or bench dies with the correct radius dies shall be approved working plans.
permitted to be used to bend tubing 20 mm (¾ in.) and 12.7.2 Valves shall be installed with clearance to ensure opera- 12.9.3.2* The pipe shall be pressurized to the normal system 13.2.1.4 The means of pipe size reduction and the attitudes of
smaller. tion of the valve from the fully closed to fully open position. operating pressure for that pipe. tees shall be checked for conformance to the design for proper
(3) Flattened bends where the larger diameter is greater than
12.7.3 All control, drain, and test connection valves shall be 12.9.3.3 After removing the source o_f pressurizing gas, the orientation.
1.08 times the least diameter shall not be permitted.
provided with permanently marked, weatherproof, metal or pressure in the pipe shall be not less than 90 percent of the test 13.2.1.5 Piping joinL<;, discharge nozzles, and piping supports
12.5.8* Pipe Hangers and Supports. Pipe hangers and rigid-plastic, identification signs, secured by corrosion-resistant pressure after 10 minutes.
wire or chain or by other approved means. shall be restrained to prevent unacceptable vertical or lateral
supports shall be designed and installed in accordance with
12.9.4 Test Report. movement during discharge.
recognized industry practices and manufacturer's instructions.
12.7.4 Valve Supervision. All valves controlling the supply of
12.9.4.1 The system review and testing shall be documented in 13.2.1.6 Discharge nozzles shall be installed in such a manner
12.5.8.1 AU pipe hangers and supports shall be attached water, inert gas agent, or hybrid media to hybrid nozzles shall
a report. that piping cannot become detached during discharge.
directly to a rigid fixed structure. be installed to accommodate the means of supervision, as speci-
fied in the working plans. 13.2.1.7 The discharge nozzles, piping, and mounting brack-
12.5.8.2 All hangers and components shaU be steel. 12.9.4.2 The report shall be maintained by the system owner
for the life of the system. et<; shall be installed ~n such a manner that they do not cause
12.7.5 Relief Valves. Relief valve discharge piping shall be
12.5.8.3 Ordinary cast-iron hangers/supports, conduit clamps, injury to personnel.
routed in accordance -with the working plans.
or "C" clamps shall not be used.
Chapter 13 Acceptance Testing 13.2.1.8 All water ahd gas storage containers shall be located
12.7.6 Check Valves. Check valves shall be installed in the
12.5.8.4 All pipe supports shall be designed and installed to direction of flow. in accordance with an approved set of system drawings.
prevent lateral movement of supported pipe during system ; 13.1 Approval of Installations.
I 13.2.1.9 All containers and mounting brackets shall be
discharge while permitting longitudinal movement to accom- 12.8 Electrical Equipment and Systems.
13.1.1 * An acceptance test plan shall be approved prior to fastened in accordance with the manufacturer's requirements.
modate expansion and contraction caused by temperature
12.8.1 Electrical equipment associated with hybrid systems scheduling of acceptance testing.
changes. 13.2.1.10 All tilters·and strainers shall be inspected for proper
shall be installed in accordance with the requirements of
13.1.2 A complete step-by-step description of the proposed location and relocated as necessary.
12.5.8.4.1 * Rigid hangers shall be installed wherever a change NFPA 70.
in elevation or direction occurs. acceptance test procedure, identifying all devices controls and 13.2.1.11 Discharge nozzles shall be inspected for minimum
12.8.2 All signaling system circuits and wiring shall be in- functions to be tested and how the test will be conducted, shall clearances to obstructions per the manufacturer's require-
12.5.8.4.2 Nozzles shall be supported so as to prevent move- stalled in accordance with NFPA 72. be approved prior to scheduling of acceptance testing. ments.
ment of the nozzle during discharge.
12.8.3 All signaling line circuits and wiring shall be installed 13.1.3* "Where a hybrid fire-extinguishing system operates in
in accordance with NJiPA 72. conjunction with other building systems, functions, or compo-

2021 Edition 2021 Edition

 770-22 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS INSPECTION, TESTING, AND MAINTENANCE 770-23

13.2.2 Review of Electrical Component.s. 13.2.4.1.2* "Where acceptable to the authority having jurisdic- 14.2 Periodic Inspection and Maintenance. (12) Check and verif)' functional operation of system inter-
tion, an alternative test method that does not require inert gas locks.
13.2.2.1 All ·wiring systems shall be checked for proper instal- 14.2.1 A manufacturer's test and maintenance procedure shall
or water to be discharged shall be permitted to confirm that
lation in conduit and in compliance with the approved draw- be provided to the owner. 14.2.4.2* Those charged with maintenance of the system shall
each nozzle discharges water and inert gas.
ings. be trained in the maintenance of the specific make and model
13.2.4.2 For systems protecting Class A fuels subject to deep- 14.2.2* Weekly Inspection.
13.2.2.2 It shall be confirmed that ac wiring and de wiring are system.
seated burning, a full discharge test shall be conducted to 14.2.2.1 At least weekly, the following shall be inspected:
not combined in a common conduit or raceway unless properly 14.2.4.3 Maintenance personnel shall review all manufactur-
verify that the design concentration of hybrid media is
shielded and grounded. (1) Inert gas and water supply lines are intact. er's service bulletins pertaining to the system.
achieved and maintained for the required retention time.
13.2.2.3* All wiring systems shalI be checked for grounding (2) Nozzles are not obstructed.
13.2.4.3 'Where a full discharge test is conducted, measure- (3) Protective caps if supplied are in place on every nozzle. 14.2.4.4 Annual maintenance results shall be recorded in an
and shielding in accordance with the working plans. inspection report that addresses, at a minimum, the require-
ment of the resultant oxygen concentration shall be permitted (4) Fire alarm control panel is in "nonnal'' ready condition.
13.2.2.4* All field circuits shall be confirmed to be free of as a means of determining the hybrid media concentration. (5) System isolation valves are locked in full open position. ments of 14.2.4.
ground faults and short circuits. (6) Tamper seals are in place. 14.3 Hose Test.
13.2.4.4 Subsequent to a flow or discharge test, all filters and
13.2.2.5 It shall be verified that the hybrid system branch strainers shall be inspected and cleaned or replaced as neces- 14.2.2.2 Any deficiencies shall be corrected. 14.3.1 All system hose shall be examined annually for damage.
piping has not been used as an electrical ground. sary.
14.2.3 Semiannual Inspection. 14.3.2 All hoses used to distribute hybrid media or its constitu-
13.2.2.6 The detection devices shall be checked for proper 13.3 System Design Information Sign. The accepting author-
14.2.3. l The following tasks, in addition to the weekly inspec- ents during discharge shall be hydrostatically tested or replaced
type and location as specified on the system drawings. ity shall confirm that the system design information sign has
tion tasks, shall be performed at least semiannually: every 5 years or whenever visual examination shows any defi-
been provided and that it accurately reflects the system design
13.2.2.7 Manual pull stations shall be confirmed as accessible, ciency, whichever occurs first.
parameters. (1) Check inert gas supply tanks for proper pressure correc-
accurately identified, and properly protected_ to prevent
ted for ambient temperature. If any tank shows a pressure 14.3.3 The test pressure shall be equal to I½ times the maxi-
damage. 13.4 Owner's Documentation. Documentation shall be provi-
loss of more than 10 percent corrected for temperature, mum system operating pressure.
ded to the owner in accordance with Section 11.4.
13.2.2.8 Abort Switches. "Where abort switches are allowed by check for the toot cause and repair or replace the tank as
14.3.4 The testing procedure shall be as follows:
the authority having jurisdiction, verify the following: necessary to provide the required quantity of inert gas in
Chapter 14 Inspection, Testing, and Maintenance storage. (1) The hose is removed from any attachment.
(1) Switches do not remain in the abort position when
(2) Check the water level in the storage tank (if applicable). (2) The hose assembly is then placed in a protective enclo-
released.
14.1 General. If the water level is more than 5 percent below design sure designed to permit visual observation of the test.
(2) Manual controls override the aborL function. (3) The hose must be completely filled with water before test-
level, check for the root cause and repair or replace the
14.1.1* The property owner or designated representative shall tank as necessary to provide the required quantity of ing.
13.2.2.9 Enclosure Integrity. For total flooding systems, the
be responsible for properly maintaining a fire protection water in storage. (4) Pressure then is applied at a rate-of-pressure rise to reach
enclosure shall be examined to verify that the number and size
system. the test pressure within 1 minute. The test pressure is
of unclosable openings are in accordance with working plans.
14.2.3.2 Any deficiencies shall be promptly corrected. then maintained for l full minute. Observations are then
14.1.2 Inspection, testing, maintenance, and impainnent
13.2.3 Functional Tests. If the system is connected to an made to note any distortion or leakage.
procedures shall be implemented in accordance with those 14.2.3.3 The results of an inspection shall be recorded on
alarm receiving office, the alarm receiving office shall be noti- both of the following: (5) After observing the hose for leakage, movement of
established in this document and in accordance with the manu-
fied that the fire system test is to be conducted and that an couplings, and distortion, the pressure is released.
facturer's instructions. (1) A record tag secured to each cylinder
emergency response by the fire department is not desired.
14.1.3 Personnel performing inspection, testing, or mainte- (2) An inspection report that addresses, at a minimum, all of 14.3.5 The hose assembly shall be considered to pass if all of
13.2.3.1 All operating devices shall be checked for proper the points of inspection outlined in 14.2.2.1 or 14.2.3.1, the following criteria are met:
nance shall be qualified in accordance with Section 4.4.
operation following directions and procedures given in the as applicable
manufacturer's installation operation and maintenance (1) No loss of pressure during the test
14.1.4 The date the inspection is performed and the initials of
manual. 14.2.4 Annual Maintenance. (2) No movement of the couplings while under pressure
the person performing the inspection shall be recorded.
(3) No permanent distortion of the hose
13.2.3.2 Proper operation of auxiliary devices such as pressure 14.1.5 Personnel making inspections shall keep records for 14.2.4.1 The following shall be performed by competent
switches, flow alarms, and pressure trips shall be verified. personnel (see 14.2.4.2) at least annually using available docu- 14.3.6 Each hose assembly that passes the hydrostatic test shall
those extinguishing systems that were found to require correc-
mentation required in Chapter 11: be marked with the date of the test.
tive actions.
13.2.3.3 Proper operation of all alanns and indicators shall be
verified. (1) Perform a functional test of the system (discharge of 14.3. 7* Each hose assembly that passed the test shall be dried
14.1.6 A completed copy of the inspection report shall be
hybrid media is not required). internally before being reinstalled.
furnished to the owner of the system or an authorized repre-
13.2.3.4 Proper operation of the fire alarm control panel and (2) Check hybrid media containers for signs of damage. (See
sentative. 14.3.8 Each hose assembly that fails the hydrostatic test shall
all connected devices such as detectors, manual stations, time Section 14. 4.)
delays, alanns, remote annunciators, and releasing devices shall be marked and destroyed.
14.1.7 Inspection, testing, and maintenance records shall be (3) Cycle all system valves (discharge of hybrid media is not
be verified. retained by the owner for the life of the system. required). 14.4* Inert Gas Agent Container Test. Inert gas storage
13.2.3.5 "Where practicable, the maximum number of systems 14.1.8* Those charged with maintenance of the system or
I (4) Clean or replace strainers and filters per system manu-
facturer's instructions.
containers shall be periodically inspected and tested in accord-
that are expected to operate in case of fire shall be in full oper- ance with this section.
using maintenance for corrective actions shall be trained in the
ation simultaneously when the adequacy and condition of the
water supply are checked.
maintenance of the specific make and model system. I (5) Check that there have been no changes to the size, type,
and configuration of the hazard and system. CAUTION
14.1.9 Maintenance personnel shall review all manufacturer's (6) Check and test all time delays for operation. Inert gas agent containers are under high pressure.
13.2.4 Flow Tests. service bulletins pertaining to, the system. (7) Check and test all audible notification appliances for Observe safety precautions when handling cylinders, including
operation.
13.2.4.l Except as permitted in 13.2.4.1.2, a flow test shall be installation of anti-recoil devices on cylinder outlets immedi-
14.1.10 The inspection, testlng and maintenance records shall (8) Check and test all visual notification appliances for oper-
conducted. ately upon disconnecting the cylinder outlet from the system
be retained for a period of 1 year after the next inspection, test, ation.
pipe and before removing the cylinder from its bracket.
or maintenance of that type required by the standard. (9) Check that all warning signs are installed and visible.
13.2.4.1.1 * The discharge from all nozzles shall be observed
to ensure the following: (10) Check operation of all manual release devices. 14.4.1 Inert gas agent containers built in accordance with U.S.
14.1.11 The inspection, testing, and maintenance records
(11) Check and test each automatic detector using methods Department of Transportation (DOT), Transport Canada (TC),
(1) Nozzle orifices are not clogged. shall be permitted to be furnished, accessed, and stored elec-
specified in NFPA 72. or similar regulatory bodies shall be periodically requalified in
(2) Nozzles are correctly positioned. tronically.

2021 Edition
2021 Edition
770-24 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS ANNEX A 770-25

accordance with the provisions of the governing regulatory 14.7 Training. 15.4 Impaired Equipment. (3) The fire department has been advised that protection is
body. restored.
14.7.1 All persons that will be expected to inspect or operate 15.4.1 The impaired equipment shall be considered to be the
(4) The property owner or designated representative, insur-
14.4.2 Inert gas agent containers continuously in service with- fire-extinguishing systems shall be trained and kept trained in fire protection system, or part thereof, that is removed from
ance carrier, alarm company, and other authorities having
out discharging shall be given a complete external visual the functions they are expected to perform. service.
jurisdiction have been advised that protection is restored.
inspection every 5 years or more frequently if required. 15.4.2 The impaired equipment shall include hybrid (water (5) The impairment tag has been removed.
14.7.2* Personnel working in an enclosure protected by a
14.4.2.1 The visual inspection shall be in accordance with hybrid system shall receive training regarding system operating and inert gas) systems. [25:15.7]
Section 3 of CGA C-6, except that inert gas agent containers procedures and safety issues.
15.5* Preplanned Impairment Programs.
need not be emptied and shall not be stamped while under Annex A Explanatory Material
14.7.3 Training for personnel working in the protected space
pressure. 15.5.1 All preplanned impairments shall be authorized by the
shall be refreshed periodically on a schedule determined by Annex A is not a part of the requirements ~f this NFPA document but is
impairment coordinator. [25:15.5.1]
14.4.2.2 The results of the visual inspection shall be recorded the system owner but not less frequently than every 12 months. included for informational purposes only. This annex contains explan-
on both of the following: 15.5.2 Before authorization is given, the impairment coordi- atory material, numbered lo correspond with the applicable text para-
14.7.4 The system owner shall maintain a record of the most
nator shall be responsible for verifying that the following graphs.
(1) A record tag attached to each cylinder recent training for each person.
procedures have been implemented:
(2) A suitable inspection report A.1.2 No standard can be promulgated that will provide all
14.8* Corrections and Repairs. (1) The extent ap.d expected duration of the impairment
14.4.2.3 A completed copy of the inspection report shall be the necessary criteria for the implementation of hybrid fire-
14.8.1* The property owner or designated representative shall have been determined. extinguishing systems. Technology in this area is under
furnished to the owner of the system or an authorized repre- (2) The areas or buildings involved have been inspected and
correct or repair deficiencies or impairments. constant development, and this will be reflected in revisions to
sentative. the increased risks determined. this standard. The user of this standard must recognize the
14.4.2.4 Container inspection records shall be retained by the 14.8.1.l Where any deficiency is noted, the appropriate (3) Recommendations to mitigate any increased risks have complexity of hybrid fire-extinguishing systems. Therefore, the
owner for the life of the system. corrective action shall be taken. been submitted to management or the property owner or designer is cautioned that the standard is not a design hand-
designated representative. book. The standard does not do away with the need for compe-
14.4.2.5 When an external visual inspection indicates that the 14.8.1.2 Where an impairment to protection occurs, the
(4) Where a fire protection system is out of service for more tent engineering judgment to be exercised in the design and
container has been damaged, the container shall be requalified procedures outlined in Chapter 15 shall be followed.
than 10 hours in a 24-hour period, the impairment coor- application of the hybrid system. It is intended that a designer
in accordance with the requirements of the applicable regula- 14.8.2 Corrections and repairs shall be performed by person- dinator shall arrange for one of the following: capable of applying a more complete and rigorous analysis to
tory body. nel qualified as required by Section 4.4. special or unusual problems shall have latitude in the develop-
(a) Evacuation of the building or portion of the build-
14.5 Water Storage Container Inspection and Test. ing affected by the system out of service ment of such designs. In such cases, the designer is responsible
Chapter 15 Impairment (b) * An approved fire watch for demonstrating the validity of the approach.
14.5.1 Water storage containers shall be subjected to an (c)* Establishment of a temporary water supply
annual external visual inspection. Al.5.4.1 It is not intended that the application or enforce-
15.1 * General. (d)* Establishment and implementation of an approved
ment of these values be more precise than the precision
14.5.2 Water storage containers shall be drained and subjec- program to eliminate potential ignition sources and
expressed.
ted to an internal inspection in accordance with 14.5.2.1 or 15.1.1 Minimum.Requirements. limit the amount of fuel available to the fire
14.5.2.2. (.1'5) The fire department has been notified. Al.5.4.2 Users of this standard should apply one system of
15.1.1.1 This chapter shall provide the minimum require-
(6) The insurance carrier, the alarm company, property units consistently and not alternate between units.
14.5.2.1 Water storage containers constructed of corrosion- ments for a fire protection system impairment program.
owner or designated representative, and other authorities
resistant material shall be inspected every 5 years. 15.1.1.2 Measures shall be taken during the impairment to having jurisdiction have been notified. A.3.2.1 Approved. The National Fire Protection Association
ensure that increased risks are minimized and the duration of (7) The supervisors in the areas to be affected have been does not approve, inspect, or certify any installations, proce-
14.5.2.2 Water storage containers that have an internal dures, equipment, or materials; nor does it approve or evaluate
the impairment is limited. [25:15.1.1.2] notified.
corrosion-resistant coating shall be inspected annually. testing laboratories. In determining the acceptability of installa-
(8) A tag impairment system has been implemented. (See
14.5.3 Water storage containers built in accordance with U.S. 15.2 Impairment Coordinator. Section 15.3.) tion~, procedures, equipment, or materials, the authority
Department of Transportation (DOT), Transport Canada (TC), (9) All necessary tools and materials have been assembled on having jurisdiction may base acceptance on compliance with
15.2.1 The property owner or designated representative shall
or similar regulatory bodies shall be periodically requalified in the impairment site. NFPA or other appropriate st.:1_ndards. In the absence of such
assign an impairment coordinator to comply with the require-
accordance with the provisions of the governing regulatory [25:15.5.2] standards, said authority may require evidence of proper instal-
ments of this chapter. [25:15.2.1]
body. lation, procedure, or use. The authority having jurisdiction
15.2.2 In the absence of a specific designee, the property 15.6* Emergency hnpainnents. may also refer to the listings or labeling practices of an organi-
14.5.4 The results of the visual inspection shall be recorded owner or designated representative shall be considered the zation that is concerned with product evaluations and is thus in
15.6.1 Emergency impairments shall include, but are not limi-
on both of the following: impairment coordinator. [25:15.2.2] a position to determine compliance with appropriate standards
ted to, interruption of water supply, frozen or ruptured piping,
(1) A record tag attached to each cylinder for the current production of listed items.
15.2.3 Where the lease, written use agreement, or manage- and equipment failure, and includes impairments found
(2) A suitable inspection report ment contract specifically grants the authority for inspection, during inspection, testing, or maintenance activities. A.3.2.2 Authority Having Jurisdiction (AHJ). The phrase
testing, and maintenance of the fire protection system(s) to the [25:15.6.1] "authority having jurisdiction," or its acronym AHJ, is used in
14.5.5 A completed copy of the inspection report shall be
furnished to the owner of the system or an authorized repre- tenant, management firm, or managing individual, the tenant, NFPA documents in a broad manner, since jurisdictions and
15.6.2* The coordinator shall implement the steps outlined in
sentative. management firm, or managing individual shall assign a person approval agencies vary, as do their responsibilities. Where
Section 15.5. [25:15.6.2]
as impairment coordinator. [25:15.2.3] public safety is primary, the authority having jurisdiction may
14.5.6 Container inspection records shall be retained by the 15.7* Restoring Systems to Service. When all impaired equip- be a federal, state, local, or other regional department or indi-
owner for the life of the system. 15.3 Tag Impairment System. ment is restored to normal working order, the impairment vidual such as a fire chief; fire marshal; chief of a fire preven-
15.3.1 * A tag shall be us~d- to indicate that a system, or part co"ordinator shall verify that the following procedures have tion bureau, labor department, or health department; building
14.6 Actuation/Impairment.
thereof, has been removed from service. [25:15.3.1] been implemented: official; electrical inspector; or others having statutory author-
14.6.1 Actuation, impairment, and restoration of the system ity. For insurance purposes, an insurance inspection depart-
(1) Any necessary inspections and tests have been conducted
shall be reported promptly to the authority having jurisdiction. 15.3.2* The tag shall be posted at each fire department ment, rating bureau, or other insurance company
connection and the system control valve, and other locations to verify that affected systems are operational. The appro-
representative may be - the authority having jurisdiction. In
14.6.2 Following actuation, the system shall be returned to required by the authority having jurisdiction, indicating which priate chapter of this standard shall be consulted for
many circumstances, the property owner or his or her designa-
service by personnel who are specifically trained and qualified system, or part thereof, has been removed from service. guidance on the type of inspection and test required.
ted agent assumes the role of the authority having jurisdiction;
to maintain the system. [25: 15.3.2]
(2) Supervisors have been advised that protection is restored.
at government installations, the commanding officer or depart-
mental official may be the authority having jurisdiction.

2021 Edition 2021 Edition

770-26 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS A.t'JNEX A 770-27

A.3.2.4 Listed. The means for identifying listed equipment A.4.1.3 Materials listed are not all inclusive, and hybrid A.4.3.5 Subsection 4.3.5 makes reference to limiting concen- Table A.4.3.5(a) Oxygen Partial Pressure at Sea Level
may vary for each organization concerned with product evalua- systems might not be appropi:iate for applications that involve trations of inert gas agents corresponding to certain values of Corresponding to Exposure Limits Given in 4.3.1 and 4.3.2
tion; some organizations do not recognize equipment as listed other materials that are not listed. Inappropriate applications "sea level equivalent" of oxygen. The mean atmospheric pres-
unless it is also labeled. The authority having jurisdiction are those where the hybrid systems are not effective (increased sure of air at sea level is 760 mm Hg (29.92 in. Hg). Atmos- Partial Pressure
Exposure Agent
should utilize the system employed by the listing organization heat absorption and/ or oxygen displacement mechanisms for pheric air is 21 volume percent oxygen. The partial pressures
Time Concentration 0 2% at Sea of 0 2
to identify a listed product. extinguishment not effective), or where the application of the of oxygen in ambient air and air diluted agent to the limiting
(min) (vol%) Level (mm Hg)
hybrid media could result in vigorous or violent reactions or sea level concentrations corresponding to permissible exposure
A.3.3. 7 Hybrid Media. Hybrid media is differentiated from a the release of hazardous compounds due to reactions with the times of 5 minutes, 3 minutes, and½ minute are given in Table Air 0 21 159.6
Lwin fluid water mist system, which uses water for cooling, water contained in the hybrid media. A.4.3.5(a). reference
vaporization, and inerting. The gas in a twin fluid system does 5 43 12.0 91.0
not play a role in the extinguishment process and only serves as A.4.2 Hybrid fire-extinguishing systems utilize both inert gas In 3.3.13.3, sea level equivalent of oxygen is defined in terms
of the partial pressure at sea level. The mean atmospheric pres- 3 52 10.1 76.6
a medium for the water to atomize. For twin fluid water mist and water to extinguish the fire. The typical inert gas design
systems, see NFPA 750. concentration will reduce the oxygen level to between sure decreases with increasing altitude, as shown in Table ½ 62 8.0 60.6
12.5 percent and 16 percent. The primary health concern of 8.4.1.3. The partial pressure of oxygen is 21 percent of the
A.3.3.9 Impairment. The use of the phrase fire protection inhalation of oxygen deficient atmospheres is asphyxiation. For atmospheric pressure. The concentration of added agent,
system or unit is a broad reference Lo those terms used in this A.5. 1.2 Quality of the water and corrosion resistance of the
nitrogen and argon, the two inert gases most likely to be used which dilutes air to the sea level limiting partial pressure of
standard and NFPA 25. Some fire protection features are refer- piping materials arc critical Lo achieve system performance.
in hybrid systems, the NOAEL is 43 percent (12 percent oxygen, is given by
red to as systems in the installation standards (e.g., sprinkler, Strainers and filters address the potential debris in piping due
oxygen) and the LOAEL is 52 percent (10 percent oxygen). to pipe joining methods and corrosion.
standpipe, water spray, foam-water, water mist, and hybrid), or
are referred to as units (e.g., fire pumps), and others use Other considerations with respect to personnel safety when [A.4.3.5]
There might be installations where strainers at the nozzles
neither term (e.g., private service fire mains and water tanks). hybrid systems are used include the following: (0.21PATM -Po, ,LIM ) I 00 arc impractical due to environmental conditions or hazards, or
01
For the purpose of this s_tandard, the term unit refers to a fire VO l ;o =: --~=-~='--x
(l) Noise. Discharge of a hybrid system can cause noise loud (0.21PATM) accessibility. In such cases, the authority having jurisdiction
pump and its connections required by NFPA 20, or a water stor- enough to be startling; however, the noise level is gener- might choose to approve their omission by specifying or requir-
age tank and its connections required by NFPA 22, or a private ally not high enough to cause permanent or traumatic ing specific quality control over the material selection, procure-
where:
service fire main and its connections required by NFPA 24. The injury. ment, installation, hybrid media, and initial system flow testing.
use of the term unit in the definitions of impairment, defi-
P,nM = local mean atmospheric pressure [mm Hg (in. Hg)]
(2) Turbulence. Discharge of a hybrid system can cause Po,,uM = limiting partial pressure of oxygen corresponding to a
ciency, critical deficiency, and noncritical deficiency is not A.5.1.3.1 The filter or strainer should be installed downstream
enough turbulence to move unsecured, light objects. sea level exposure time limit [mm Hg (in. Hg)]
referring to an individual component such as a sprinkler, valve, ( on the system side) of all piping that is not corrosion resistant.
(3) Temperature/Visibility. Discharge of a hybrid can cause
fitting, switch, piece of pipe, and so forth. [25, 2017] The effect of altitude on limiting agent concentrations is A filter· or strainer with mesh openings meeting the require-
reduction in temperature and visibility. Visibility will
given in Table A.4.3.5(b) and Figure A.4.3.5. ments of 5.1.4 should be installed downstream (on the system
Temporarily shutting down a system as part of performing return to predischarge state when the temperature in the
side) of any reservoirs of stored water or break tank with an
the routine inspection, testing, and maintenance on that enclosure rises above the dew point temperature.
(4) Wetting of Surfaces. "When discharged under fire condi-
A.5.1.1 The water is required to be equivalent in quality to air-water interface greater than 1 m 2 (10.8 ft'}
system while under constant attendance by qualified personnel, potable water. The particular hazard being protected or the
and where the system can be restored to service quickly, should tions, some or all of the water droplets will evaporate to A5.2 It is recommended to have and in some instances the
application might dictate a higher quality of water such as
not be considered an impairment. Good judgment should be steam resulting in little or no wetting of surfaces. Some authority having jurisdiction might require a reserve quantity
distilled, deionized, or demineralized. In these cases, the stor-
considered for the hazards presented. [25, 2017] wetting of surfaces, however, is possible particularly if of inert gas when the time to recharge the inert gas source will
age of water and piping must be compatible with the type of
there is little heat present to evaporate the water droplets. unacceptably impact continuation of operations within the
A.3.3.9.1 Emergency Impairment. Examples of emergency water being used. For example, wet bench applications or
Caution is advised when walking on surfaces that might protected space.
impainnents might include a _ruptured pipe, an operated sprin- other applications where contamination of process materials
have been wetted by the discharge. Electrical energy
kler, or an interruption of the water_supply to the system. [25, could occur due to the use of ionized water, circulating deion-
could be conducted across wetted surfaces.
ized water should be used.
2017]
A.4.3.4 Many studies have been conducted and technical guid-
A.3.3.14.2 Maximum Operating Pressure. The operating ance has been published regarding occupant egress time
Table A.4.3.5 (b) Relationship of Altitude to Atmospheric Pressure, Oxyge~ Partial Pressure in Air, and Limiting Agent
pressure to which portions of the hybrid system will be subjec- prediction. One source of such information is the SFPE Hand-
Concentration
ted could vary depending on the location of pressure reducing book qf fi'ire Protection Engineering. Various approaches are de-
devices on the pipe serving the inert gas supply and various scribed that can be used by a designer to calculate the available
other system specific conditions. The maximum operating pres- safe egress time (ASET) from a space protected by a clean Limiting Agent Concentration
sure is intended to reflect the highest pressure to which each agent extinguishing system. The ASET value can then be (vol%)
component or section of pipe, including hoses where used, compared to the required safe egress time (RSET), which is the Altitude Above 0 2 Partial
would be subjected. maximum allowed exposure time limit in 4.3. l and 4.3.2. The 5 min Exposure
Sea Level PATM Pressure in Air 3 min Exposure 30 sec Exposure
ASET ·value should be less than the RSET value. If the ASET
A.3.3.15.2 Pre-Engineered Systems. These systems have the
value· is initially determined to be equal to or greater than the
(ft) (mm Hg) (mm Hg) =
P(O,) 91 mm Hg =
P(O 2) 76,6 mm Hg =
P(O 2) 60.6 mm Hg
agent quantity, flow rates, specific pipe size, maximum and
RSET value, the facility should be modified so that the ASET -3,000 840 176.4 48.4 56.6 65.6
minimum pipe lengths, flexible hose specifications, number of
value is less than the RSET value. Alternatively, a study involv- -2,000 812 170.5 46.6 55.1 64.5
fittings, and number, types, and locations of nozzles prescribed
ing a timed recording of an egress simulation in the protected -1,000 787 165.3 44.9 53.7 63.3
by a testing laboratory. All other provisions of this standard are
space is considered an acceptable means of verifying compli- 0 760 159.6 43.0 52.0 62.0
to be followed. Based on actual test fires, the hazards protected
ance with the maximum allowed exposure time limits. 1,000 733 153.9 40.9 50.2 60.6
by these systems are specifically limited as to type and size by a
testing laboratory. Limitations on hazards that are allowed to 2,000 705 148.1 38.5 48.3 59.1
be protected by these systems are contained in the manufactur- 3,000 679 142.6 36.2 46.3 57.5
er's installation manual, which is referenced as part of the list- 4,000 650 136.5 33.3 43.9 55.6
ing. 5,000 622 130.6 30.3 41.4 53.6
6,000 596 125.2 27.3 38.8 51.6
7,000 570 119.7 24.0 36.0 49.4
8,000 550 115.5 21.2 33.7 47.5
9,000 528 110.9 17.9 30.9 45.3
10,000 505 106.l 14.2 27.8 42.9

2021 Edition 2021 Edition

 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS ANNEX A 770-29
770-28

A.5.6.9.6 Where installations could he exposed to conditions i. Valves, fittings, and filters
that could lead to loss of integrity of the pneumatic lines, n. Power requirements
special precautions should be taken to ensure that no loss of iii. Operating pressure and flow rates
~ 60 1---+--+----t==+-=f----+--+--f---+--+-----t--+---+ integrity will occur. iv. Water requirements
§Z
00
------ -- ---- .
-----
.....
r=====t=~==r=-,=1~::t-=j=-1--'r=1=:::::1===t=:j
A.6.1 At the time this standard was developed, system design
methods for hybrid extinguishing systems were different
( d) Cylinders, as follows:
i. Valves and fittings
9:-,_
~C
so
40
-- ____ _ __
l---+----l-------tc---=::::e1---~+--+------l-----_-=-i==-lc---+--+--f-----1
beLween manufacturers and could differ from the methods
prescribed in this standard. The relationship between flux
ii.
iii.
Capacity
Operating pressures
density or nozzle spacing and perfonnance in controlling fires
~c i--.._
I - - - .____
----
-- is not consistent between systems designed by different manu-
A.6.2.1 Requirements for complete hybrid extinguishing
8 30 >-----+--1-------1----1---1-----1-----l---::-:0.,,._=---t----l-----+---=----f-.=--j systems, including fire test protocols, system component test

------
facturers. Features such as nozzle spacing, flow rate, droplet
procedures, and the manufacturer's design, installation, opera-
t i--- size distribution, cone angle, and other characteristics need to
tion, and maintenance manual review, have been published in
g, 20 ---1---+---+----'1------l---+---+--+--+--+-=---i--==-+------I be determined for each manufacturer's system through full-
~
a,
--........... scale fire testing, representative of the hazard to be protected,
FM 5580. Other listing organizations generally apply their own
requirements.
~ 10 --l--+--+---+---+---+---+-f--f---f---t--+---+--7 to obtain a listing or to be approved for each specific applica-
tion. A.6.2.2 The test fire hazard reflects the application specified.
E
0 L___j__ __J__ _ L_ _L__ _j__ _l__ _ L _ _ l - _ _ l_ _j__
Test fires should be chosen such that the performance objec-
_ L_ ___L_ _J
A.6.2 The results of the listing testing should identify the
tive (i.e., fire extinguishment) of the system can be deter-
-3000 -2000 -1000 a 1000 2000 3000 4000 5000 6000 7000 8000 9000 10,000 following, as applicable: mined. Fire tests are conducted inside an enclosure, as
Altitude relative to sea level (ft) (1) System flow rate (mmimum and maximum), as follows: applicable, and test fires should be chosen such that the influ-
(a) Flow rate per unit area ence from the enclosure is minimized.
- - - Maximum IG concentration where maximum exposure time (MET) :s: 5 minutes
- - - - Maximum IG concentration where MET :s: 3 minutes
(b) Flow rate per unit volume A.6.2.3.2 Enclosure variables include, but are not limited to,
··········-- Maximum IG concentration where normally unoccupied and MET :s: 30 seconds (c) Water-to-inert ratio height, volume, obstructions, and ventilation. Fire hazard prop-
(2) System pressure, as follows: erties include, but are not limited to, fuel type and fuel config-
(a) Nozzle operating pressure range uration. Occupancy status is an indication of whether the
FIGURE A.4.3.5 Inert Gas Limiting Agent Concentrations at Altitude. (b) Pump/cylinder operating pressure range application is intended to be nonnally occupied, normally
(c) Pump inlet and outlet pressure and flow rate unoccupied, or unoccupiable.
requirements
A.5.4.2.1 Hybrid systems consist of two agents. Some hybrid tion is not required and in MSS SP-127 for locations where seis- A.6.4.1 The construction of the _enclosure should substantially
(3) General water requirements, as follows:
systems mix the agents at the container location and use one mic qualification is required. contain the hybrid media in the vicinity of the hazard for a
piping netvmrk to carry the hybrid mixture to the nozzle. (a) Quantity/duration sufficient length of time to achieve the fire protection objec-
A.5.6.8.2 One objective of predischarge alarms and time (b) Quality tives of the hybrid extinguishing system. As with other water-
Other hybrid systems use independent pipe networks to carry delays is to prevent human exposure to atmospheres with
the separate agents to the nozzle where they are mixed. (c) Temperature based systems, consideration should be given to account for the
oxygen concentrations lower than 19.5 percent. Where a (4) General inert gas requirements, as follows: pressure changes developed during the tire and the hybrid
Some plastic pipe materials, such as CPVC and PVC, are not predischarge time delay is required, it should delay the media discharge.
discharge of the system for sufficient time to allow evacuation (a) Quantity/duration
appropriate for use with compressed gases, and the failure (b) Quality
mode could be catastrophic. The designer should consider the of personnel from areas within the spaces most remote from A.6.4.1.2.1 Natural ventilation and openings in the enclosure
(c) Temperature allow the hot gases layer ( ceiling jet) to exhaust hybrid media
pipe manufacturer's recommendations for the specific media the exits.
(5) Nozzle characteristics, as follows: from the compartment, decreasing the extinguishing potential.
or agent being used and the maximum service pressure. Hazards associated with fast growth fires would indude, but
(a) Type(s)/model number(s) The flow of gases into and out of the compartment alters the
A.5.4.3.1 The designer should consider credible failure not be limited to, flammable liquid storage or transfer areas mixing characteristics of the system, which might require the
(b) Flow rate (minimum and maximum)
scenarios that could require pressure relief, such as failure of a and aerosol filling areas. (c) Operating pressure range additional momentum of the hybrid media in order to over-
pressure regulator, a flow-control valve, or system controls. A.5.6.8.4 Abort switches are a means of delaying automatic (6) Nozzle spray characteristics, as follows: come the alteration. Forced ventilation also significantly
agent release. The function of an abort switch should be reduces the amount of hybrid media in the compartment and
A.5.4.4.2.2 Paragraph 5.4.4.2.2 requires that "the thickness of (a) Spray angle
approved by the authority having jurisdiction. The following affects the mixing characteristics of the system.
the piping shall be calculated in accordance with ASME B31.1." (b) Drop size distribution
This does not imply that all the provisions of ASME B31.1 are two abort functions have been approved by listing agencies. (c) Momentum/velocity Prior to or concurrent with the operation of the hybrid
to be applied. Rather it indicates that the formula for pipe wall Other abort functions might be possible. (7) Nozzle installation parameters, as follows: extinguishing system, consideration should be given to auto-
thickness shall be used. ASME B31.1 also provides tables of (1) UL - A releasing event starts a predischarge timer. If the (a) Distance above floor (minimum and maximum) matic closing of doors and dampers, shutdown of electrical
allowable stress values for various metallic pipe materials. abort switch is activated, the timer counts down to (b) Distance below ceiling (minimum and maximum) equipment, and shutdown of HVAC equipment.
10 seconds and holds there. When the abort switch is (c) Distance above hazard (minimum and maximum)
To comply with the requirement of 5.4.4.2.2, the guidelines A.6.4.1.2.1.1 Examples of such openings include, but ate not
released, the timer resumes the countdown from (d) Nozzle spacing (minimum and maximum)
found fn the FSSA Pipe Design Handbook for Use with Special limited to, doors and windows.
10 seconds and is irreversible. (e) Orientation
Hazard Fire Suppression Systems should be followed. The FSSA
(2) IRI - The abort type functions the same way as the UL (f) Minimum distance from walls A.6.4.1.2.1.2 Examples of such precautions could include, but
Pipe Design Handbook for Use wzth Special Hazard Fire Suppression
type, except that the abort switch will not function unless (g) Minimum distance from obstructions are not limited to, automatic door closures and hybrid media
Systems provides guidance on how to apply ASME B31.1 in a
it is activated before a second input device is activated in (8) Activation device, as fo1lows: curtains.
uniform and consistent manner in the selection of acceptable
types of pipe and tubing used in special hazard fire suppression a "cross-zone" detectio1,1 scheme.
(a) Type/model number A.8.2.2 Unclosable openings in the enclosure membrane
systems. A.5.6.9.1 Required auxili~ry functions include any functions (b) Alarm temperature or alarm smoke obscuration should not exceed the manufacturer's tested tolerance.
that must occur to ensure effective control or extinguishment level
A.5.4.11.2 FSSA's Pipe Design Handbook for Use with Special A.8.2.3.1 The effect on the water mist density due to filters or
of fire. Examples of required auxiliary functions could- be (9) General design parameters, as follows:
Hazard Fire Suppression Systems provides guidance on pipe hang- equipment installed in a self-contained recirculating ventilation
power disconnect, fuel shut-off, HVAC control, damper
ers and supports, following established industry practices. Addi- (a) Pipe sizes and design pressures/wall thicknesses system should be considered.
tional guidance based on best industry standard practices is closure, door closure, and the like.
(b) Fitting types and design pressures
found in ANSI/MSS SP-58 for locations where seismic qualifica- (c) Pumps, as follows: A.8.3.1(4) The time to extinguishment is intended to be less
thah the design discharge time.

2021 Edition
2021 Edition
770-30 HYBRID (WATER AND INEKr GAS) FIRE-EXTINGUISHING SYSTEMS AL"'\JNEX A 770-31

A.8.4. 1.2 The Hooding factor can be calculated in accordance Another important variable is the fuel configuration. While A.12.5.8.4.1 A single rigid hanger could be designed to
with the following equation: wood cribs and pallets are e_asily extinguished with Class A support multiple changes in direction.
design concentrations, vertical wood panels closely spaced and
A12.6.4 The strainer or filter can be integral to supplied
parallel can require higher concentrations and long hold times
[A.8.4.1.2] system components.
for extinguishment. Fires in boxes of excelsior and in piles of
shredded paper also can require higher concentrations and A.12.9.2.6 Verification of the connection between the device
20.95]
X~In - - long hold times for extinguishment. In these situations, heat and the pipe can be achieved by visual inspection or test.
( Co,9gni tends to be retained in the fuel array rather than being dissipa- Sensors installed in nitrogen piping can be verified by a pneu-
ted to the surroundings. Radiation is an important mechanism matic test of the piping system or an abbreviated discharge
where: for heat removal from smoldering fires. using inert gas only.
X == flooding factor (m 3 /m 3 )
In order to cool deep-seated fires and to prevent re-ignition Al2.9.3.2 The pressure test is intended to identify any major
Coxygen = design concentration of oxygen at 21 °C ( % vol/vol)
of a surface fire, the extinguishing concentration of the hybrid leaks in the pipeline that might compromise the proper opera-
A.8.4.2.1 A shorter time to discharge the minimum volume of media must be maintained in a defined hazard zone that incor- tion of the system. It is not intended to be a proof pressure test
inert gas could be more appropriate for a specific hazard. The porates the anticipated fire location(s). of the strength of the pipeline. The nonnal operating pressure
risk of delayed extinguishment should be weighed against the is the expected pressure in the pipeline during discharge. On
A.9.3.2 Test and performance data can be obtained from the Note: All dimensions in mm.
effects of increasing the system discharge rate (e.g., enclosure systems that have a high-pressure inert gas supply manifold as
manufacturer.
pressurization). well as low-pressure piping, the test pressure for the respective
FIGURE A.12.5.7 Installation Measurements for Application
A.9.5.2 Examples of hazards with a mechanical rundown time sections of pipe should correspond to the normal operating
A.8.4.3 The calculated number of nozzles could differ from ofTahleA-12.5.7. pressure at ambient temperature for that section of pipe.
include ventilation and rotating equipment.
the number required by each nozzle manufacturer's listing or
design guidance. Consult each nozzle's manufacturer's manual A9.5.4 Most flammable liquids have a boiling point below the A.13.1.1 "When a hybrid fire-extinguishing system is integrated
A.12.5.8 The FSSA Pipe Design Handbook for Use with Special
for area of coverage and any other requirements that could autoignition temperature of the fuel. The maximum tempera- with other fire protection and life safety systems, NFPA 3
Hazard Ji'ire Suppresswn Systems provides guidance on pipe hang-
affect the nozzle quantity. ture of the liquid mass is limited to the boiling point. Some should be referenced for incorporation of the acceptance test
ers and supports, following established industry practices. Addi-
fuels, ho_wever, have boiling points above their autoignition into the commissioning plan.
AS.6.1 Two types of fires can occur in solid fuels: (1) one in tional guidance based on "best industry standard practice" is
temperature. These fuels will burn before they boil, and the
which volatile gases resulting from heating or decomposition of found in ANSI/MSS SP-58 for locations where seismic qualifica-
temperature of the mass of fuel might continue to rise above
the fuel surface are the source of combustion and (2) one in tion is not required or in MSS SP-127 for locations where seis-
the autoignition temperature. The resultant "super-heated"
which oxidation occurs at the surface of or in the mass of fuel. mic qualification is required.
mass of fuel will be subject to re-ignition until the fuel has
The first type of fire is commonly referred to as "flaming"
cooled below its autoignition temperature.
combustion, while the second type is often called "smoldering"
or "glowing" combustion. The two types of fires frequently The time required for the temperature of such fuels to drop TahleA.12.5.7 Recommended Minimum Bending Radii for Different Sizes of Tube
occur concmTently, although one type of burning can precede below the autoignition temperature depends on the mass and
the other. For example, a wood fire can start as flaming configuration of the fuel.
combustion and become smoldering as burning progresses. Wall Thickness,
Leg Length Length
Bending Radius,
A.11.1.5(15) Critical system application criteria define the (mm) (mm)
Conversely, spontaneous ignition in a pile of oily rags can begin TuheO.D. Tolerance± s TuheI.D. ·R Weight
as a smoldering fire and break into flames at some later point. design basis of the system. This could include the hybrid media (mm) L, L,
(mm) (nun) (mm) (nun) a h (kg/piece)
density, target flow rate, or other criteria that are critical to fire
Flaming combustion, because it occurs in the vapor phase, extinguishment. 16 0.08 2 12 30 200 40 230 70 0.198
can be extinguished with relatively low levels of hybrid media. 18 0.08 1.5 15 36 200 35 236 71 0.178
In the absence of smoldering combustion, it will stay out. A-11.4 Owner's documentation should provide information to 20 0.08 2 16 36
the user or a third party to verify that the system has been
200 45 236 81 0.268
Unlike flaming combustion, smoldering combustion is not 20 0.08 2.5 15 36 200 45 236 81 0.326
subject to immediate extinguishment. Characteristic of this designed and installed properly. Manuals also should include
operation and maintenance instntctions for each piece of
22 0.08 1.5 19 38 200 40 238 78 0.227
type of combustion is the slow rate of heat losses from the reac-
tion zone. Thus, the fuel remains hot enough to react with equipment or device of the as-built system. 22 0.08 2 18 38 200 40 238 78 0.296
oxygen, even though the rate of reaction, which is controlled 25 0.08 2 21 44 200 50 244 94 0.362
A.11.5.1 Permanent markers do not meet the intent of this
by diffusion processes, is extremely slow. requirement, as the ink can degrade over time. 25 0.08 2.5 20 44 200 50 244 94 0.442
25 0.08 3 19 44 200 50 244 94 0.519
Smoldering fires can continue to burn for many weeks -for A.12.5.2 Pipe segments should be cleaned prior to installa- 28 0.08 1.5 25 48 200 50 248 98 0.319
example, in bales of cotton and jute and heaps of sawdust. A tion. After pipe installation, the system should be flushed with
smoldering fire ceases to burn only when either all the availa- water or a compressed gas to remove any remaining debris 28 0.08 2 24 48 200 50 248 98 0.417
ble oxygen or fuel has been consumed or the fuel surface is at prior to nozzle installation. 28 0.08 3 22 48 200 50 248 98 0.601
too low a temperature to react. Smoldering fires usually are 30 0.08 2.5 25 50 200 60 250 110 0.575
extinguished by reducing the fuel temperature, either directly A.12.5.3 It is essential that pipe sealants, tape, or lubricants 30 0.08 3 24 50 200 60 250 110 0.677
by application of a heat-absorbing medium, such as water, or by not be allowed to enter the pipe network. By leaving the first 30 0.08 4 22 50 200 60 250 110 0.869
blanketing with an inert gas. The inert gas slows the reaction thread on the end of a pipe devoid of sealant, tape, or lubri-
rate to the point where heat generated by oxidation is less than cant, the possibility of these substances entering the pipe 35 0.15 2 31 60 200 65 260 125 0.586
heat losses to surroundings. This causes the temperature to fall network and plugging small orifices in control devices or 35 0.15 3 29 60 200 65 260 125 0.852
below the level necessary for spontaneous ignition after discharge nozzles is greatly r:,educed. 38 0.15 2.5 33 65 200 75 265 140 0.827
removal of the inert atmosphere. 38 0.15 3 32 65 200 75 265 140 0.979
A-12.5.7 See Figure A.12.5.7 and Table A.12.5.7.
38 0.15 4 30 65 200 75 265 140 1.268
For the purposes of this standard, smoldering fires are divi-
ded into two classes: (1) where the smoldering is not deep 38 0.15 5 28 65 200 75 265 140 1.538
seated and (2) deep-seated fires. "Whether a fire will become 42 0.2 2 38 80 200 85 280 165 0.809
deep seated depends, in part, on the length of time it has been 42 0.2 3 36 80 200 85 280 165 1.183
burning before application -of the extinguishing agent. This 50 0.2 6 38 180 150 150 310 310 3.451
time is usually called the "pre burn'' time. 65 0.35 10 45 250 160 160 330 330 9.840

2021 Edition 2021 Edition I

Ii'
I;

:I
770-32 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS ANNEX B 770-33

A.13.1.3 Where a hybrid fire-extinguishing system operates in (1) If any work is to be performed on the fire suppression required by rescue pe-.--sonnel should accidental discharge A.15.5 The need for temporary fire protection, termination of
conjunction with other building systems, functions, or compo- system, qualified fire service personnel, trained and expe- occur all hazardous operations, and frequency of inspections in the
nents, the final testing should be conducted simultaneously rienced in the type of equipment installed, should be areas involved should be determined ..All work possible should
A.14.8 Needed correctioris and repairs should be classified as
with those systems per NFPA 4. engaged to do the work. be done in advance to minimize the length of the impairment.
an impairment, critical deficiency, or noncritical deficiency
(2) Personnel involved with fire suppression system cylinders Where possible, temporary feedlines should be used to main-
A.13.2.2.3 Proper shielding and grounding is particularly according to the effect on the fire protection system and the
must be thoroughly trained in the safe handling of the tain portions of systems while work is completed.
important if ac and de wiring are combined m a common nature of the hazard protected.
containers as well as in the proper procedures for installa-
conduit or raceway. tion, removal, handling, shipping, and filling; and Fire protection systems should not be removed from service
Impairments are the highest priority problem found during
connection and removal of other critical devices, such as when the building is not in use. vVhere a system that has been
A.13.2.2.4 Where measming field circuitry, the following inspection, testing, and maintenance and should be corrected
discharge hoses, control heads, discharge heads, initia- out of service for a prolonged period, such as in the case of idle
should apply: as soon as possible. The fire protection system cannot provide
tors, and anti-recoil devices. or vacant properties, is returned to service, qualified personnel
an adequate response to a fire, and implementation of impair-
(l) All electronic components, such as smoke and flame (3) The procedures and cautions outlined on the cylinder should be retained to inspect and test the systems.
ment procedures outlined in Chapter 15 is required until the
detectors or special electronic equipment for other detec- nameplates and in the operation and maintenance impairment is corrected. A.15.5.2(4)(b) A fire watch should consist of trained person-
tors or their mounting bases, should be removed. manuals, owner's manuals, service manuals, and service nel who continuously patrol the affected area. Ready access to
(2) Jumpers should be installed properly to prevent the possi- bulletins that are provided by the equipment manufac- Critical deficiencies need to be corrected in a timely fashion.
fire extinguishers and the ability to promptly notify the fire
bility of damage within these devices. turer for the specified equipment installed should be The fire protection system is still capable of performing, but its
department are important items to consider. During the patrol
(3) All components should be replaced after measuring. followed. performance can be impacted and the implementation of
of the area, the person should not only be looking for fire, but
(4) Most fire suppression system cylinders containing agent impairment procedures might not be needed. However, special
A.13.2.4.1.1 For engineered systems, the pressure at the most making sure that the other fire protection features of the build-
under pressure are furnished with valve outlet anti-recoil consideration must be given to the hazard in the determination
remote nozzle should be measured and verified to be in ing such as egress routes and alann systems are available and
devices and in some cases cylinder valve protection caps. of the classification. A deficiency that is critical for one hazard
accordance with the manufacturer's specifications. functioning properly. [25A I 5.5.2 (4)(b) J
Do not disconnect cylinders from the system piping or might be an impairment in another.
A.13.2.4.1.2 Alternative test methods could include the follow- move or ship the cylinders if the anti-recoil devices or A.15.5.2(4)(c) Temporary water supplies are possible from a
Noncritical deficiencies do not affect the performance of the
ing: protection caps are missing. Obtain these parts from the number of sources, including use of a large-diameter hose
fire protection system but should be corrected in a reasonable
distributor of the manufacturer's equipment or the from a fire hydrant to a fire department connection, use of a
( 1) Flo\Vl.ng through a dedicated test nozzle time period so that the system can be properly inspected,
equipment manufacturer. These devices are provided for portable tank and a portable pump, or use of a standby fire
(2) Flowing inert gas through the water supply piping, in lieu tested, and maintained.
safety reasons and should be installed at all times, except department pumper and/or tanker. [25:A.15.5.2(4) (c) J
of water
when the cylinders are connected into the system piping Ai,sembly occupancies, health care facilities, prisons, high-
(3) Flo\Vl.ng air, in lieu of inert gas or water A.15.5.2(4)(d) Depending on the use and occupancy of the
or being filled. rise buildings, other occupancies where the life safety exposure
build_ing, it could be enough in some circumstances to stop
A.14.1.1 Any portion or all of the inspection, testing, and (5) All control heads, pressure-operated heads, initiators, is significant, or facilities that cannot be evacuated in a timely
certam processes in the building or to cut off the flow of fuel to
maintenance can be permitted to be contracted with an inspec- discharge heads, or other type of actuation devices should manner require special consideration. As an example, a
some machines. It is also helpful to implement "No Smoking"
tion, testing, and maintenance service. When an inspection, be removed before disconnecting the cylinders from the nonfunctioning waterflow alarm might be considered a critical
and "No Hot Work" (cutting, grinding, or welding) policies
testing, and maintenance service company agrees to perform system piping, and anti-recoil devices and/ or protection deficiency in a stornge warehouse but an impairment in a
while the system is out of service because these activities are
inspections and tests at a specific frequency required by this caps should be immediately installed before the cylinders hospital.
responsible for many fire ignitions. [25:A.15.5.2(4) (d)]
standard, the inspection, testing, and maintenance service are moved or shipped. Fire suppression system equip-
ment often varies from manufacturer to manufacturer; High hazard occupancies where early response to a fire is
company should perform all inspections and tests that are A.15.6 Emergency impairments include, but are not limited
therefore, it is important to follow the instructions and critical also require special consideration. A small number of
required more frequently than the specified frequency. For to, system leakage, interruption of water supply, frozen or
painted sprinklers could be considered an impairment for a
example, the ITM service provider agrees to perform required procedures provided in the specific eqmpment manufac- ruptured piping, equipment failure, or other impairments
turer's manuals. The preceding procedures should be system protecting a high hazard occupancy but might be
inspections and tests on an annual basis. Those inspections and found during inspection, testing, or maintenance activities.
undertaken only by qualified fire suppression system serv- considered a critical deficie_ncy in a metal working shop.
tests required on a daily, weekly, quarterly, and semiannual [25:A.15.6]
frequency should also be performed during the annual inspec- ice personnel. A.14.8.1 System deficiencies not explained by normal ·wear
tions and tests. (6) Safety is of prime concern. Never assume that a cylinder is A.15._6.2 When one or more impairments are discovered
and tear, such as hydraulic shock, can often be indicators of
empty. Treat all cylinders as if they are fully charged. Inert during inspection, testing, and maintenance activities, the
system problems and should be investigated and evaluated by a
A.14.1.8 It is essential that personnel be trained to maintain gas cylinders are under high pressure and can produce owner or owner's authorized representative should be notified
qualified person or engineer. Failure to address these issues
the specific make and model of the system in accordance with high discharge thrusts out of the valve outlet if not in writing.
could lead to catastrophic failure.
the system manufacturer's guidelines. handled properly. Remember, pressurized cylinders are A.15.7 Occasionally, fire protection systems in idle or vacant
extremely hazardous. Failure to follow the equipment A.15.1 The general model for impairment procedures is based
A.14.2.2 An inspection of the system is a quick check to give buildings arc shut off and drained. When the equipment is
reasonable assurance that the extinguishing system is fully manufacturer's instructions and the guidelines contained o?- Chapter 15 of NFPA 25. It is recognized that hybrid systems eventually restored to service after a long period of not being
charged and operable. It is done by seeing that the system is in herein can result in serious bodily injury, death, or prop- will commonly exist alongside water-based fire protection
maintained, it is recommended that qualified personnel or a
place, that it has not been actuated or tampered \Vl.th, and that erty damage. systems and should follow essentially the same impairment
qualified contractor perform the work.
procedures.
there is no obvious physical damage or condition to prevent A.14.7.2 Training should cover the follo\Vl.ng:
operation. This quick check of the system will generally be ~15.3.1 A clearly visible tag alerts building occupants and the
done by the owner's representative. (1) Health and safety hazards associated with exposu_re to Annex B Fire Test Methods
fire department that all or part of the fire protection system is
extinguishing agent caused by inadvertent system This annex is not a part of the requirements of this NFPA document
A.14.2.4.2 It is ·essential that personnel be trained to maintain out of service. The tag should be weather resistant, plainly visi-
discharge ble, and of sufficient size [typically 100 mm x 150 mm ( 4 in. x but is included for informational purposes only.
the specific make and model of the system in accordance \Vl.th (2) Difficulty in escaping spaces with inward swinging doors 6 in.)]. The tag should identify which system is impaired, the
the system manufacturer's guidelines. that are overpressurized due to an inadvertent system B.1 General.
da~e and time impairment began, and the person responsible.
A.14.3.7- If heat is used for drying, the temperature should not discharge
(3) Possible obscuration Of vision during system discharge
B.1.1 The purpose·ofthis annex is to provide a recommended
A.15.3.2 An impairment tag should be placed on the fire
exceed the manufacturer's specification. test procedure for determining the inert gas flooding factor, X,
( 4) Need to block open doors at all times during mainte- department connection to alert responding fire fighters of an
as described in 8.4.1, for a hybrid nozzle or array of hybrid
A.14.4 One of the major causes of personnel injury and prop- nance activities abnormal condition. An impairment tag that is located on the
nozzles used to protect a specific fuel or hazard type \Vl.th a
erty damage is attributed to the improper handling of agent (5) Need to verify that a clear escape path exists to compart- system riser only could go unnoticed for an extended period if
fixed flow rate of water and a fixed flow rate of inert ga.s agent.
containers by untrained and unqualified personnel. In the ment access fire fighters encounter difficulty in gaining access to the build-
interest of safety and to minimize the potential for personnel (6) A review of how the system could be accidentally ing or sprinkler control room. [25:A.15.3.2] B.1.2 The characteristics identified in 8.3.1 should be recor-
injury and property damage, the following guidelines should discharged during maintenance, including actions ded, as part of the testing program.
be adhered to:

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770-34 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS ANNEX B 770-35

B.1.3 The flooding factor determined in accordance with this B.3.4.3 The test enclosure should have unclosable openings, B.4.1.2 Polymeric Materials Fuel Array. B.4.1.2.5 The fuel array should be_ orienLed such that the
method should be applied as a baseline value for fire extin- such that the total open are_a represents the manufacturer's 203 mm (8 in.) dimension of the fuel array is parallel to the
B.4.1.2.1 The test should be conducted for each of the follow-
guishment testing during the listing process. maximum specified limit for the system or nozzle. 610 mm (24 in.) side of the fuel shield.
ing polymeric fuels, having properties as specified in Table
B.2 Flooding Factor. B.3.4.3.1 At least 40 percent of the open area should be loca- B.4.1.2.1: B.4.1.2.6 Two external baffles measuring 1.0 m x 1.0 m x
ted 305 mm (12 in.) or less below the ceiling. (I) Poly(methyl rnethacrylate) (PMMA) 0.3 m tall (40 in. x 40 in. x 12 in. tall) should be located around
B.2.1 The inert gas flooding factor, X, for a specific fuel or the exterior of the fuel shield, as shown in Figure B.4.1.2.6.
B.3.4.3.2 At least 40 percent of the open area should be loca- (2) Polypropylene (PP)
hazard type to be protected by a hybrid nozzle or system should
ted 305 mm (12 in.) or less above the Hoar. (3) Acrylonitrile-butadiene-styrene polymer (ABS) B.4.1.2.6.1 The baffles should be placed 89 mm (3.5 in.)
be established through testing.
B.4.1.2.2 Each polymeric fuel array should consist of 4 sheets above the floor.
B.2.2 The inert gas flooding factor at sea level should be B.3.5 Extinguishing System.
of polymeric material that are 9.5 mm thick x 406 mm tall x B.4.1.2.6.2 The lower baffle should be oriented with its sides
determined in accordance with the following equation: B.3.5.1 The exLinguishing system should be assembled such 203 mm wide (¾ in. thick x 16 in. tall x 8 in. wide) each. parallel to the fuel shield.
that the nozzle(s) operates at the manufacturer's specified
[B.2.2] conditions, including minimum operating pressure and mini- B.4.1.2.3 Sheets should be spaced and located as shoWn in B.4.1.2.6.3 The top baffle should be rotated 45 degrees with
mum discharge rate of water. Figure B.4.1.2.3. respect to the lower baffle.
X B.4.1.2.4 A fuel shield, consisting of a 381 mm wide x 851 mm
B.3.5.2 v\There multiple nozzles are used, nozzles should be B.4.2 Ignition Source. The ignition source should be a square
evenly distributed throughout the enclosure in accordance high x 610 mm deep (15 in. wide x 33.5 in. high x 24 in. deep) steel pan, 51 mm x 51 mm x 22 mm deep (2 in. x 2 in. x ½ in.
with the manufacturer's design manual. channel iron frame with sheet steel on the top and on the two deep), containing commercial grade heptane, centered 12 mm
where: 851 mm high x 610 mm deep (33.5 in. high x 24 in. deep)
X = flooding factor at sea level and 21 °C (70°F) ambient (0.5 in.) below the bottom of the polymeric sheets.
B.3.6 Fuel Location. The test fuel should be located where it sides, should be provided around the fuel array as indicated in
temperature [m 3 /m 3 (ft3 /ft 3 )] will minimize the effects of local application. B.4.2.1 The amount of heptane should provide at least
Figure B.4.1.2.3.
v;n,,, w,s = volume of inert gas component of the discharged 90 seconds of burning.
hybrid media [m 3 (ft3 )] B.4 Tests with Class A Fuels.
3 3
V,,.,,1aswF = volume of the test enclosure [m (ft )]
B.4.1 Test Fuels. Class A fuels used for testing should
ACF= atmospheric correction factor from Table 8.4.1.3 for comprise three wood cribs and three polymeric material fuel Table B.4.1.2.1 Plastic Fuel Properties
the elevation of the test enclosure arrays for each of the three polymeric materials.
B.2.3 The flooding factor, )(, as determined by the manufac- B.4.1.1 Wood Crib. 25 kW/m 2 Exposure in Cone Calorimeter ASTM E1354
turer for Class A fires should be validated based on all tesL'>
recommended in Section B.4. B.4.1.1.1 The wood crib should be assembled from four layers 180-Second Average Heat Effective Heat of
of six trade size 50 mm x 50 mm x 450 mm (2 in. x 2 in. x Ignition Time Release Rate Combustion
B.2.4 The flooding factor, X, as determined by the manufac- 18 in.) long kiln spruce or fir lumber having a moisture Density Tolerance Tolerance Tolerance
turer for Class B fires should be validated based on all tests content between 9 and 13 percent. Fuel Color (g/cm2) sec (%) kW/m 2 (%) MJ/kg (%)
recommended in Section B.5.
B.4.1.1.2 The individual wood members in each layer should PMMA Black 1.19 77 ±30
B.3 General Test Parameters. 286 25 23.3 ±15
be evenly spaced, forming a square determined by the specified Natural
length of the wood members. pp 0.905 91 ±30 225 25 39.8 ±15
B.3.1 Extinguishment. The primary criteria should be (white)
complete extinguishment of fire within the test enclosure. B.4.1.1.3 Alternate layers of the wood members should be Natural
ABS 1.04 115 ±30 484 25 29.1 +15
placed at right angles to one another. (cream)
B.3.1.1 For Class A fire tests, both of the following criteria
should be observed: B.4.1.1.4 The wood members forming the out.side edges of
(I) The fire is extinguished before the end of discharge. the crib should be stapled or nailed together.
(2) Flaming combustion does not reignite after the enclosure B.4.1.1.5 Ignition of the crib should be achieved by the burn- 203 mm x 406 mm x 9.53 mm
is ventilated in accordance with B.4.4.
ing of commercial grade heptane in a square steel pan 0.23 m 2 (8 In. x 16 in. x 3/o in.) plastic sheet
B.3.1.2 For Class B fire tests, fires should be extinguished in
less than 30 seconds after the end of discharge.
(2.5 ft 2) in area and not less than 101.6 mm (4 in.) in height. k---- 610 mm (24 in.) _ __, r-- 381 mm (15 in.)--,
Fuel shield - channel iron
B.4.1.1.6 The heptane fire should burn for 3 to 3½ minutes;

IT
frame covered with
B.3.2 Discharge Time. The hybrid media should be approximately 0.95 L (¼ gal) of heptane will provide a 3 to 3½ 254mm sheet metal on top and two
disc.barged· within 180 seconds, or in accordance with the ~ (10 in.) ---i sides
minute burn time.
manufacturer's design discharge time. 8.5 mm(% in.)1-+-->1--Angle frame
B.4.1.1.7 The crib should be centered with the bottom of the +-I I_.,
B.3.3 Conditioning. crib 304 mm to 609.6 mm (12 in. to 24 in.) above the top of the
3.2 mm(% in.) allthread rod fuel support
pan and the test stand should be constructed such that the
B.3.3.1 Hybrid media components, including nitrogen cylin-
bottom of the crib is exposed to the atmosphere. 51 mm square x 22 mm deep
ders and water supply, should be conditioned to 21 °C ± 3°C
(2 in. square x 3/a in. deep)
(70°F ± 5°F) prior to the test fire. B.4.1.1.8 Once the heptane is ignited, the crib should be (internal) n-heptane
allowed to burn freely for approximately 6 minutes outside the igniter pan
B.3.3.2 The enclosure should be maintained at 21 °C ± 3°C
test enclosure.
(7D°F ± 5°F) prior to the ignition of the test fire.
B.4.1.1.9 Just prior to the,~nd of the preburn period, the crib
B.3.4 Enclosure. should be moved into the test enclosure and centered on a
12mm
B.3.4.1 Testing should be conducted in an enclosure having a stand such that the bottom of the crib is between 508 mm and 1l (Y, in.)
volume equal to the maximum spacing and protected volume 711 mm (20 in. and 28 in.) above the floor.
for the quantity of nozzles used. Drip tray
Load cell
B.3.4.2 The test enclosure should have a volume no less than
100 m 3 (3530 ft 3 ). FIGURE B.4.1.2.3 Four-Piece Modified Plastic Setup.

2021 Edition 2021 Edition

770-36 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS ANNEX C 770-37

Annex C Informational References C.1.2.3 FM Approvals Publications. FM Approvals, 1151

l 0,3m
C.1 Referenced Publications. The documents or portions
thereof listed in this annex are referenced within the informa-
Boston-Providence Turnpike, P.O. Box 9102, Nonvood, IvIA
02062 (www.fmapprovals.com).
External baffles, (12 in.) FM 5580, Approval Standard for Hybrid (Water and Inert Gas)
tional sections of this standard and are not part of the require-
/rotated 45 degrees
to each other _,________, J ments of this document unless also listed in Chapter 2 for
other reasons.
Fire Extinguishing Systems, 2012.

V External
baffles C.1.1 NFPA Publications. National Fire Protection Associa-
tion, l Batterymarch Park, Quincy, IvIA 02169-7471.
C.1.2.4 FSSA Publications. Fire Suppression Systems Associa-
tion, 3601 E.Joppa Road, Baltimore, MD 21234 (www.fssa.net).
FSSA Pipe Design Handbook for Ufe with Special Hazard Fire
NFPA 3, Standard for Commissioning of Fire Protection and Life Suppression S)'stems, 2nd edition, 2011.
Safety System~, 2021 edition. C.1.2.5 MSS Publications. Manufacturers Standardization
NFPA 4, Standard for Integrated Fire Protection and Life Safety Society (MSS) of the Valve and Fittings Industry, 127 Park
System Testing, 2021 edition. Street NE, Vienna VA 22180-4602.
PLAN VIEW ELEVATION VIEW
NFPA 20, Standard fur the Installation of Stationary Pumps for ANSI/MSS SP-58, Pipe Hangers and Supports - 1Waterials,
Fire Protection, 2019 edition. Design, A1anufacture, Selection, Application, and Installation, 2018.

FIGURE B.4.1.2.6 External Baffles. NFPA 22, Standard }Or Water Tanks for Private Fire Protection, MSS SP-127, Bracing for Piping Systems: Seismic-Wind-Dynamic
2018 edition. Design, Selection, and Application, 2014a.

B.4.2.2 The hybrid media discharge should be started B.6 Data Documentation. NFPA 24, Standard for the Installation of Private Fire Service C.1.2.6 SFPE Publications. Society of Fire Protection Engi-
210 seconds after ignition of the heptane. Mains and Their Appurtenances, 2019 edition. neers, 971 I Washingtonian Boulevard, Suite 380, Gaithersburg,
B.6.1 The foHowing data should be recorded during testing:
MD 20878.
B.4.3 Heptane Used as an Ignition Source in Class A Fire (1) Inert gas agent discharge rate of the hybrid nozzle NFPA 25, Standard for the Inspection, Testing, and Maintenance
Tests. The heptane should have the following characteristics: (2) Water discharge rate of the hybrid nozzle q[Water-Based Fzre Protection Systems, 2020 edition. SFPE Handbook of Fire Protection Engineenng, 5th edition, 2016.
(1) Minimum initial boiling point: 90°C (194°F) (3) Volume and dimensions of the test enclosure C.2 Informational References. The following documents or
( 4) Areas and locations of unclosable openings NFPA 750, Standard on Water Mist Fire Protection Systems, 20 I 9
(2) Maximum dry point: l0O'C (212°F) portions thereof are listed here as infonnational resources
(5) Test enclosure's elevation above sea level edition.
(3) Specific gravity: 0.67-0.73 only. They are not a part of the requirements of this document.
(6) Number and locations of nozzles C.1.2 Other Publications.
B.4.4 Post-Discharge Ventilation. At 600 seconds after the (7) Time of fuel ignition Raia, Peter and Michael]. Gollner, Literature Review on Hybrid
start of discharge, the enclosure should be ventilated to return (8) Time of discharge start C.1.2.1 ASME Publications. American Society of Mechanical Fire 5,;uppressiun Systems, University of MD/Fire Protection
the oxygen concentration to pretest conditions, and the fuel (9) Time of discharge end Engineers, Two Park Avenue, New York, NY 10016-5990. Research Foundation, May 2014.
package should be observed for reignition for a period of (10) Time to extinguishment
60 seconds. ASME B31.l, Power Piping, 2016. VdS 2562en, Procedure for the approval of new extinguish-ing tech-
(11) Starting oxygen concentration
niques, VdS Schadenverhiitung GrnbH, Amsterdamer Str.
B.5 Tests with Class B Fuels. (12) Ending oxygen concentration C.1.2.2 ASTM Publications. ASTM International, 100 Barr
I 72-174, 50735 K61n, Germany, 2013-03.
(13) Total inert gas discharged Harbor Drive, P.O. Box C700, West Conshohocken, PA
B.5.1 Tests for Class B fllels should be considered valid only (14) Total water discharged 19428-2959. C.3 References for Extracts in Informational Sections.
for those specific fuels and fuel conditions that were included
B.6.2 The oxygen concentration should be recorded continu- ASTM E1354, Standard Test Method.for Heal and Visible Smoke NFPA 25, Standard }Or the Inspection, Testing, and Maintenance
in the test.
ously during the test on a dry basis measurement. Release R.ates for Matenals and Products Using an Oxygen Consump- of Water-Based Fire Protection Systems, 2017 edition.
B.5.1.1 Pans or trays should be constructed of steel at ]east tion Calorimeter, 201 7.
6.5 mm (¼ in.) thick, with joints welded and liquidtight, nomi- B.6.2.1 Oxygeri measurements should be recorded within the
nally 99 mm (3.9 in.) high, with no lip. endosure at the fuel source, at a minimum.

B.5.1.2 A water base of nominally 48 mm (1.9 in.) should be B.6.2.2 Additional locations for oxygen measurement are
used, with a fuel load of at least 20 mm (0.8 in.). allowed.

B.5.1.3 Freeboard should be nominally 31 mm (1.2 in.). B.6.3 At the time of system discharge, the oxygen concentra-
tion in the enclosure at the fuel source should be within
B.5.1.4 Tests should be perfonned three times for at least 0.5 percent by volume _of the normal oxygen level at atmos-
each of the following pan sizes: pheric conditions.
(1) 152.5 mm (6 in.) round B.6.4 The oxygen concentration should be measured within a
(2) 254 mm (10 in.) round distance of 1 m (40 in.) from the fuel source edge.
(3) 356 mm (14 in.) round
B.6.4.1 For the wood crib, the oxygen concentration should
B.5.2 The pan should be located on the test enclosure floor. be measured at the height equivalent to the bottom of the fuel
B.5.3 The pan should be placed at the center of exterior source.
baffles constructed and arranged in accordance with B.4.1.2.6. B.6.4.2 For the polymeric (uel array, the oxygen concentration
B.5.4 A fuel shield, consisting of a 610 mm x 610 mm (24 in. x should be measured at the" height equivalent to the middle of
24 in.) plate of sheet steel supported at a height of 851 mm the polymeric sheets of the polymeric fuel array.
(33.5 in.) from the floor to the bottom of the plate by a chan- B.6.4.3 For the heptane pans, the oxygen concentration
nel iron frame, should be centered above the pan. should be measured at the height equivalent to the top of the
B.5.5 The heptane should be ignited and allowed to burn pan.
freely for 30 seconds.

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 r
770-38 HYBRID (WATER AND INERT GAS) FIRE-EXTINGUISHING SYSTEMS INDEX 770-39

-D- General Test Parameters, B.3

Index
Deficiency Conditioning, B.3.3
Copyright© 2020 National Fire Protection Association. All Right.s Reseived. Critical Deficiency Discharge Time, B.3.2
Defimtion, 3.3 2.1 Enclosure, B.3.4
The copyright in this index is separate and distinct from the copyright in the document that it indexes. The licensing provi- Extinguishing System, B 3.5
Defmition, 3.3.2
sions set forth for the document are not applicable to this index. This index may not be reproduced in whole or in part by any Extinguishment, B.3.1
Noncritical Deficiency
means without the express written permission of NFPA. Fuel Location, 8.3.6
Definition, 3.3.2.2
-A- Design, Installation, Operation, and Maintenance Design Requirements for Local Application Systems, Chap. 9 Tests with Class A Fuels, 8.4
Manual, 6.2.6 Discharge Rate, 9.4 Heptane Used as an Igmtjon Source m Class A Fire
Acceptance Testing, Chap. 13 Tests, B.4.3
Fire Test Protocols, 6.2.2, A.6.2.2 Discharge Time, 9.5
Acceptance Requirements, 13.2 Ignition Source, B 4.2
General, 6.2.1, A.6.2.1 General, 9.1
Flow Test5, 13.2.4 Post-Discharge Ventilation, B.4.4
Testmg, 6.2.5 Application Characteristics, 9.1.4
Functional Tests, 13.2.3 Test Fuels, B 4.1
Performance Objectives, 6.3 Descnption, 9.1.1
Review of Electrical Components, 13.2.2 Polymeric Materials Fuel Array, B.4.l.2
Approved General Requirements, !::l.1.3
Abort Switches, 13 2.2.8 Wood Crib, B.4.1.1
Definition, 3.2.l, A.3 2.1 Safety Req111remenLs, 9.1 5
Enclosure lnlcgnty, 13.2.2.9 Tests with Cla.ss B Fuels, B.5
Authority Having Jurisdiction (A.HJ) Uses, 9.1.2
Review of Mechanical ComponenL5, 13.2.1
Definition, 3.2.2, A.3.2.2 Hazard Specifications, 9.2
Approval oflnst.allations, 13.1 -G-
Extent of Hazard, 9.2. l
Owner's Docurncntatjon, 13.4 -C- General Information, Chap. 4
Flammable Liquid Hazards, 9.2.3
System Design Information Sign, 13.3 Qualifications, 4.4
Classes of Fire Location of Hazard, 9.2.2
Administration, Chap. 1 Safety Considerations, 4.2, A.4.2
Class A Fire Hybrid Media Quantity, 9.6
Equivalency, 1 4 Use and Limitations, 4.1
Definition, 3.3.1.1 Nozzle Selection, Quantity, and Location, 9.3
Purpose, 1.2, A.1.2 Pre-Engineered Systems, 4.1.4
Class B Fire Design Requirements for Total Flooding Systems, Chap. 8
Retroactivity, 1 3 Temperature Lim1t.s, 4.1.5
Defimtion, 3.3.1.2 Concentration of Oxygen, 8 5
Scope, l.1 Use Restrictions, 4.3
Class C Fire Enclosure Requirements, 8.2
Units of Measurement, 1.5 Alt1tude Considerations, 4.3.5, A.4 3.5
Definition, 3.3.1.3 Enclosure Integrity and Loss of Hybrid Media, 8.2 2, A.8 2.2
Measurement of Pressure, 1.5.3 Nonnally Occupied Areas, 4.3.l
Definition, 3 3.1 Enclosure Strength and Pressure Relief~ 8.2.l
Primary Units, 1.5.1 Nonnally Unoccupied Areas, 4.3.2
Components, Chap. 5 Forced-Air Ventilation Systems and Loss of Hybrid
Secondary Units and Conversions, l.5.2 Unoccupiable Areas, 4.3.3
Detection, Actuauon, Alarm, and Control Systems, 5.6 Media, 8.2.3
Unit Application and Enforcement, 1.5.4
Automatic Detection, 5.6.5 General, 8.1
Application and Fire Test Protocols, Chap. 6 -H-
Control Equipment, 5.6.9 Description, 8.1.l
Application Parameters, 6.4 Hybrid Fire-Extinguishing System
Disconnect Switch, 5.6.9.8 Uses, 8.1.2
Fire Hazard Classification, 6.4.2 Definition, 3.3.6
Electric Actuator Supervision, 5.6.7 Hybrid Media Quantity, 8.4
Combustible Loading, 6.4.2.1 Hybrid Media
Operating Alarms and Indicators, 5.6.8 Hybrid Media Retention for Prevention of Re-ignition, 8.6
Fuel Type, 6.4.2.2 Definition, 3.3.7, A.3.3.7
Operating Devices, 5.6.6 Hybrid Nozzle Selection, Quantity, and Location, 8.7
Class A Fires, 6.4.2.2.3 Hybrid Nozzle
Hyb1id Nozzles, 5.5 System Perfonnance Characteristics, 8.3
Class B Fires, 6.4.2.2.4 Definition, 3.3.8
Inert Ga.s Agent Supply, 5.2, A.5.2 Protection of Class A, Class B, and Class C Hazards, 8.3.i
Class C Fires, 6.4.2.2.5
Pipe, Fittrngs, and Valves, 5.4 Protection of Mixed Hazards, 8.3.2.
Combination Fires, 6.4.2.2.6 -I-
Drain, 5.4.9 Dvf
Fire Hazard Characteristics, 6.4.2.2.2 Impairment, Chap. 15
Fittmgs and Piping Connections, 5.4.5 Definition, 3.3.3
Fire Hazard Classification, 6.4.2.2.l Definition, 3.3.9, A.3.3.9
General, 5.4]
Fire Location, 6.4.3 .£. Emergency lmpa1nnent
Identification ofValves, 5.4.10
Obstructions and Shielding, 6.4.4 Enclosures Definition, 3.3.9.1, A.3.3.9.1
Lockout Valve, 5.4.8
Total Flooding Enclosure Variables, 6.4 1, A.6.4.1 Definition, 3.3.4 Emergency Impairments, 15.6, A.15.6
Pipe Hangers/Supports, 5.4.11
Enclosure Geometry, 6.4.1.1 Normally Occupied Enclosure or Space General, 15.1,A.15.1
Pipe Requirements, 5.4.4
Ventilation, 6.4.1.2 Definition, 3.3.4.1 Minimum Requirements, 151.1
Pressure Rating Design Requirement.s, 5.4.2
Forced Ventilat10n, 6.4.1.2.2 Occupiable Enclosure or Space Impaired Equipment, 15.4
Pressure Relief, 5.4.3
Natural Ventilation, 6.4.1.2.1, A.6.4.l.2.l Definit10n, 3.3.4.2 Impairment Coordinator, 15.2
Strainers or Filters, 5.4.6
Flooding Factor, 6.5 Unoccupiable Enclosure or Space Preplanned Impairment
Valves, 5.4. 7
General, 6.1,A.6.l Definition, 3.3.4.3 Definit10n, 3.3.9.2
Storage Containers, 5.3
Application Characteristics, 6.1.2 Preplanned Impairment Programs, 15.5, A.15.5
Water Supply, 5.1
Application Evaluations, 6.1.3 -F- Restoring Systems to Service, 15.7, A. 15.7
Filter Rating or Strainer ¥esh Openings, 5.1.4
Listing or Approval, 6.1.1 Fire Extinguishment Tag lmpainnent System, 15.3
Filters and Strainers for,Nozzles, 5.1.2, A.5.1.2
Pre-Engineered Systems, 6.1.4 Definition, 3.3.5 Inert Gas Agent
Filters and Stramers for Water Supply Connect.Ions, 5.1.3
Listing or Approval Evaluations, 6.2, A.6.2 Fire Test Methods, Annex B Definition, 3.3.10
Quahty,5.l.l,A.5.11
Applicability, 6.2.4 Data Documentation, B.6 Inspection, Testing, and Maintenance, Chap. 14
Application Parameters, 6.2.3 Floodmg Factor, B.2 Actuation/Impairment, 14.6

2021 Edition 2021 Edition

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770-40 HYBRID (WATER AND INERT GAS) F1RE-EXTINGUISHING SYSTEMS Sequence of Events for the Standards Committee Membership
Development Process Classijications· 2•3•4
Corrections and Repairs, 14.8, A.14.8 -0-
Once the current edition is published, a Standard is o/Jened f0r The following classifications apply to Committee members
Definition, 3 3.11 Occupant Safety Public Input. and represent their principal interest in the activity of the
Hose Test, 14.3 Definition, 3.3.13
Committee.
Inen Gas Agent Con tamer Test, 14.4, A.14.4 Lowest Observable Adverse Effect Level (LOAEL) Step 1 - Input Stage
Inspection Defimt1on, 3.3.13.1 • Input accepted from the public or other committees for 1. M j\lfanufaclurer: A representative of a maker or mar-
Definition, 3.3.11.l No Obsen;ed Adverse Effect Level (NOAEL) consideration to develop the First Draft keter of a product, assembly, or system, or portion
Maintenance Definition, 3.3.13 2 • Technical Committee holds First Draft Meeting to revise thereof, that is affected by the standard.
Definition, 3.3 11.2 Sea Level Equivalent of Oxygen Standard (23 weeks); Technical Committee(s) with Cor- 2. U User: A representative of an entity that is subject to
Periodic Inspection and Maintenance, 14.2 Defirntton, 3.3.13.3 relating Committee (10 weeks) the provisions of the standard or that voluntarily
Annual Maintenance, 14.2.4 • Technical Committee ballots on First Draft (12 weeks); uses the standard.
Semiannual Inspection, 14.2.3 -P- Technical Committee(s) with Correlating Committee 3. IM lnstaller/1\llaintainer: A representative of an entity that
Weekly Inspection, 14.2.2, A.14.2.2 Pressure (11 weeks) is in the business of installing or maintaining a prod-
Testmg Defimtion, 3.3.14 • Correlating Committee First Draft Meeting (9 weeks) uct, assembly, or system affected by the standard.
Definition, 3.3.11.3 Maximum Allmvable Working Pressure • Correlating Committee ballots on First Draft (5 weeks) 4. L Labor: A labor representative or employee concerned
Training, 14. 7 Definit.1on, 3.3.14.1 • First Draft Report posted on the document information with safety in the workplace.
Water Storage Contamer Inspection and Test, 14.5 Maximum Operating Pressure page 5. RT Applied Research/Testing Laboratory: A representative
Installation Requirements, Chap. 12 Definition, 3.3.14.2, A.3.3.14.2 Step 2 - Comment Stage of an independent testing laboratory or indepen-
Electncal Clearances, 12.4 dent applied research organization that promulgates
-S- • Public Comments accepted on First Draft (10 weeks) fol- and/ or enforces standards.
Electncal Equipment and Systems, 12.8
lowing posting of First Draft Report 6. E Enforcing Authority: A representative of an agency or
Gas and Water Storage Contamers, 12.6 Shall
• If Standard does not receive Public Comments and the an organization that promulgates and/ or enforces
Accessibility, 12.6.1 Definition, 3.2.5
Technical Committee chooses not to hold a Second Draft standards.
Container-Securement, 12.6.3 Should
meeting, the Standard becomes a Consent Standard and 7. I Insurance: A representative of an insurance company,
Storage Temperatures, 12.6.2 Definition, 3.2.6 is sent directly to the Standards Council for issuance (see
Standard
broker, agent, bureau, or inspection agency.
Strainers and Filters, 12.6.4, A.12.6.4 Step 4) or 8. C Consumer: A person who is or represents the ultimate
General, 12.1 Definition, 3.2.7 • Technical Committee holds Second Draft Meeting purchaser of a product, system, or service affected by
Qualifications, 12.1.5 System Design Methods (21 weeks); Technical Committee(s) with Correlating the standard, but who is not included in (2).
Working Plans, 12.] .4 Definition, 3.3.15 Committee (7 weeks) 9. SE Special l!,Xpert: A person not representing (1) through
Hazardous Locations,-12.3 Engineered Systems • Technical Committee ballots on Second Draft (11 weeks); (8) and who has special expertise in the scope of the
Nozzles, 12.2 Definition, 3.3.15.1 Technical Committee(s) with Correlating Committee standard or portion thereof.
Pipe Network, 12.5 Pre-Engineered Systems (10 weeks)
Flexible Components, 12.5.fl Definition, 3.3.15.2, A.3.3.15.2 • Correlating Committee Second Draft Meeting (9 weeks)
• Correlating Committee ballots on Second Draft NOTE 1: "Standard" connotes code, standard, recom-
Installation Standards, 12.5.4 System Design Requirements, Chap. 7
(8 weeks) mended practice, or guide.
Pipe Hangers and Supporl.s, 12.5.8, A.12.5.8 Pipe Network Layout and Design, 7.2
Pipe Identification, 12.5.l System Documentation, Chap. 11 • Second Draft Report posted on the document informa- NOTE 2: A representative includes an employee.
Piping Slope Requirements, 12.5.10 Detection, Actuatton, and Control Systems Documentation, 11.3 tion page NOTE 3: While these classifications will be used by the
Pressure Rating, 12.5.5 Owner's Documentation, 11.4, A.11.4
Step 3 - NFPA Technical Meeting Standards Council to achieve a balance for Technical Com-
System Drainage, 12 5.9 System Flow Documenration, 11.2 mittees, the Standards Council may determine that new
• Notice of Intent to Make a Motion (NIT:MAM) accepted classificitions of member or unique interests need repre-
Tube Bending, 12.5.7, A.12.5.7 Detailed Work Sheets, 11.2.4
(5 weeks) following the posting of Second Draft Report sentation in order to foster the best possible Committee
System Review and Testing, 12.9 Engineered Systems, 11.2.2
• NITMAMs are reviewed and valid motions are certified deliberations on any project. In this connection, the Stan-
Pressure Test of Pipe, 12.9.3 Pre-Engineered Systems, 11.2.1
by the Motions Committee for presentation at the NFPA dards Council may make such appointments as it deems
Review of Installation, 12.9.2 Srimrnary Sheets, 11.2.3
Technical Meeting appropriate in the public interest, such as the classification
Test Report, 12.9.4 System Information Sign, 11.5
• NFPA membership meets each June at the NFPA Techni- of "Utilities" in the National Electrical Code Committee.
Valves and Pressure Gauges, 12.7 System Working Plans, 11.l cal Meeting to act on Standards with "Certified Amend-
Check Valves, 12 7.6 As-Bwll Plans, 11.1.6 ing Motions" (certified NITMAMs) NOTE 4: Representatives of subsidiaries of any group are
ReliefValves, 12.7.5 Component Identification, 11.1.4 • Committee(s) vote on any successful amendments to the generally considered to have the same classification as the
Valve Supemsion, 12.7.4 Deviations from Approved Plans, 11.1.2 Technical Committee Reports made by the NFPA mem- parent organization.
Qualifications, 11.l.3 bership at the NFPA Technical Meeting
-L- Required Information, 11.l.5
Labeled Submittal of Working Plans, 11.l.l
Step 4 - Council Appeals and Issuance of Standard
Definition, 3.2.3 • Notification of intent to file an·appeal to the Standards
Listed -W- Council on Technical Meeting action must be filed within
Definit10n, 3.2.4, A.3.2.4 Water Mist 20 days of the NFPA Technical Meeting
Lockout Valve Definilion, 3.3.16 • Standards Council decides, based on all evidence,
Definition, 3.3.12 Working Plans whether to issue the standard or to take other action
Definition, 3.3.17 Notes:
1. Time periods are approximate; refer to published sched-
ules for actual dates.
2. Annual revision cycle documents with certified amend-
ing motjons take approximately 101 weeks to complete.
3. Fall revision cycle documents receiving certified amend-
ing motions take approximately 141 weeks to complete.
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