Health Care

Facility Design
Resource
 © Copyright 2003
Phoenix Controls Corporation

Reproduced with permission from AIA, Washington, DC 20006.

Copyright 2003, American Society of Heating, Refrigerating and Air-Conditioning, Engineers, Inc. www.ashrae.org.
Reprinted by permission from ASHRAE 2003 Handbook-Fundamentals.

The material in this paper is for information purposes only and is subject to change without notice. Phoenix Controls
Corporation assumes no responsibility for any errors or for consequential damages that may result from the use,
misrepresentation, or translation of any of the material in this publication.

Printed in USA
Phoenix Controls
Health Care Facility Design Resource

Introduction..................................................................................... 3

Ventilation Requirements ........................................................... 5

Airflow Control Solutions .......................................................... 9

System Components.................................................................... 17

Standards and Guidelines ......................................................... 23

 Introduction
Introduction
Ventilation controls for directional airflow and room pressurization can provide effec-
tive protection for patients, staff, and visitors against the risk of infection from airborne
pathogens. However, it is worth noting that engineering controls are but one of three
types of controls for an effective infection control program, the other two being admin-
istrative and personal respiratory protection.
While concerns surrounding the spread of tuberculosis (TB) in health care settings have
existed for a number of years, recent outbreaks of Severe Acute Respiratory Syndrome
(SARS) in several countries and preparedness in response to potential bioterrorism
attacks have heightened interest in infection control.
This document addresses important considerations for ventilation controls and offers
application solutions using Phoenix Controls systems. Topics covered include:
• Room airflow patterns
• Room airflow control
• Ventilation rates
• Monitoring
Several organizations issue guidelines in health care facilities, including government agen-
cies, the architectural community and an engineering technical society. Guidelines rel-
evant to ventilation have been excerpted and compiled into one handy reference that
may be found in Chapter 5 of this document. In addition, be sure to consult local fire
codes for any isolation room control that is in contradiction with smoke control in the
event of a fire.

Phoenix Controls Health Care Facility Design Resource 3

4 Phoenix Controls Health Care Facility Design Resource
 Table of Contents
• Pressurization Control Approach, 7
This chapter provides details on the ventilation
requirements that are unique to health care • Ventilation Rates, 7
facilities. • Room Pressurization Monitoring , 7

Ventilation Requirements
Hospitals and health care facilities have many different types of specialized functional
spaces to fulfill patient needs. General ventilation systems should be designed to flow
from more clean to less clean areas. However, certain areas require higher levels of

Requirements
Ventilation
infection control, necessitating continuous control of airflow direction. Below is a sample
list of room types and their pressure relationships to adjacent areas:
Surgical and critical care areas:
Operating room Positive
Delivery room Positive
Nursery suite Positive
Bronchoscopy Negative
Triage Negative
Ancillary:
Laboratory, general Negative
Laboratory, pathology Negative
Laboratory, serology Positive
Autopsy Negative
Nursing:
Protective environment Positive
Airborne infection isolation Negative
Isolation anteroom Positive/Negative1
Airborne infectious isolation rooms are used to prevent the spread of infection from the
patient to others, and therefore have inward directional airflow making the room nega-
tively pressurized. Examples of use would be for patients with tuberculosis or smallpox.
The airflow for protective environments (PEs) flows outward from the room to the
adjacent space, keeping potential infection from the patient and thus are positively
pressurized. For example, PE would be used for organ transplant recipients or burn
patients.
When an immunocompromised patient also requires airborne infection isolation, then
an anteroom is required. The anteroom provides additional protection against escaping
pathogens when the doors are opened and closed. In each situation, directional airflow is
achieved by maintaining the desired pressure relationship between the room and the
corridor, and/or an anteroom.
There are three common approaches to anteroom relative pressurization according to
1 the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
American Society of Heating, Refrigerating
and Air-Conditioning Engineers (ASHRAE), with the preference for having the anteroom positive to the room and its surrounding
2003 ASHRAE Handbook: HVAC Applica-
tions, p. 7.6. space for protective environments.2 The American Institute of Architects (AIA) states

Phoenix Controls Health Care Facility Design Resource 5

 that “there is no prescribed method for anteroom ventilation” but the
advantage of a clean anteroom is that health care workers need not mask
before entering the anteroom. Both seem to favor option 1 below, with
the anteroom positively pressurized and air moving from it to the patient
room and corridor.
1. The anteroom is positive to the patient room and corridor. (This
approach corresponds to the “Protective Environment with
Airborne Infectious Isolation” application on pages 13-14.)

Patient room (-) Anteroom (+) Corridor (-)

2. The anteroom is negative to the surrounding space. (This approach

corresponds to the “Protective Environment with Airborne Infec-
tious Isolation” application on pages 15-16.)

Patient room (+) Anteroom (-) Corridor (+)

Filtration
Ventilation controls are normally supple-
3. The anteroom is positive to the room and negative to the corridor.
mented with high-efficiency particulate
air filtration (HEPA) on either the ex-
(This approach corresponds to the “Infectious Isolation Environ-
haust side (infectious) and/or supply side ment with an Anteroom Negative to the Corridor” application on
(protective). These air-cleaning devices pages 12-13.)
are capable of removing 99.97% of par-
ticles greater than or equal to 0.3 mi- AII with Anteroom
crons in diameter. For more information,
see the “Filtration” section of the stan-
dards and guidelines on page 31. Patient room (-) Anteroom (+)
(-) Corridor (+)
Ultraviolet germicidal irradiation (UVGI)
may be used to provide supplemental
engineering control. Units may be in-
stalled in the exhaust air ducts or on or
near the ceiling to irradiate upper room
air. While not recommended as a pri-
mary infection control measure, UVGI is
most often used against mycobacterium
tuberculosis (TB).

2
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE), 2003 ASHRAE Handbook: HVAC Applica-
tions, p. 7.3.

6 Phoenix Controls Health Care Facility Design Resource

Pressurization Control Approach
The magnitude of the pressure differential recommended by the Centers for Disease
Control (CDC) for infectious isolation and protective environments is .01 inch water
gauge (2.5 Pa) in relation to the adjacent space. While it is agreed that it is the difference
in air pressure between two adjacent rooms that causes air to flow from inside or
outside of a room, how that differential is controlled may be approached two different
ways. One method, called volumetric offset, relies on the laws of physics by exhausting a
volume of air greater (or lesser) than supply volume, thereby creating an “offset,” hence
the name of the approach. The second method, known as differential pressure sensing,
employs a mechanical sensing device to measure the pressure within the two spaces and
based on that, controls the amount of supply and exhaust air delivered to the space.

Requirements
Ventilation
Both approaches create a pressure differential; however, based on years of controlling
pressurization in critical laboratory environments, Phoenix Controls has found volu-
metric offset to be a very stable, reliable method of control. Differential pressure sensing
has historically been more difficult, less stable and dependent on sensor accuracy and
maintenance. In the Z9.5-2003 standard, the American National Standards Institute (ANSI)
and the American Industrial Hygiene Association (AIHA) support the use of volumetric
offset over differential pressure for laboratory environments: “...specifying quantitative
pressure differential is a poor basis for design…What really is desired is an offset air
volume. Attempts to design using direct pressure differential measurement and control
vs. controlling the offset volume may result in either short or extended periods of the
loss of pressure when the doors are open or excessive pressure differentials when the
doors are closed, sufficient to affect the performance of the low pressure fans.”3

Ventilation Rates
For new construction, a minimum of 12 air changes per hour (ACH) for infectious and
protective isolation rooms is recommended. Anterooms and toilet rooms may be slightly
less at 10 ACH. Many existing facilities may have lower ACH because prior to 2001, the
minimum was 6 ACH. For more information, see the “Air Change Rates” section of the
standards and guidelines on page 26.

Room Pressurization Monitoring

A permanently installed, visual and audible device is recommended to ensure that the
patient room is pressurized as specified. The product developed for use with the Phoenix
ventilation system measures the pressure differential between two adjoining spaces to
within 0.5% of full scale and displays the measurement to 0.0001 inches of water gauge
(0.0249 Pa). A time delay of up to 30 seconds may be used to prevent nuisance alarms
caused by the opening of doors into the room. Remote monitoring and documentation
of pressure status is also possible by integrating operating information with the building
management system. Monitoring of valve feedback may be advantageous to verify the
3
American Industrial Hygiene Association
stability of the room pressurization versus the volumetric offset. This signal may also be (AIHA). American National Standard for
integrated to the building management system. Laboratory Ventilation (ANSI/AIHA Z9.5-
2003), pp. 28-29.

Phoenix Controls Health Care Facility Design Resource 7

8 Phoenix Controls Health Care Facility Design Resource
 Table of Contents
• Infectious Isolation Environment
without an Anteroom, 9
• Protective Environment without
an Anteroom, 10

This chapter describes ventilation control options and • Infectious Isolation Environment with
applications designed to meet the special airflow require- an Anteroom Negative to Corridor, 12
ments of health care facilities. • Protective Environment with Airborne
Infectious Isolation (positive anteroom), 13
• Protective Environment with Airborne
Infectious Isolation (neg. anteroom), 15
Airflow Control Solutions
A broad array of control sequences may be used to meet the specialized airflow require-
ments of health care facilities. Five of these are presented in this section:
• Infectious isolation environment without an anteroom
• Protective environment without an anteroom
• Infectious isolation environment with an anteroom negative to the corridor
• Protective environment with airborne infectious isolation (the anteroom is positive
to the patient room and the corridor)
• Protective environment with airborne infectious isolation (the anteroom is negative
to the patient room and the corridor)

Airflow Control
Infectious Isolation Environment without an

Solutions
Anteroom
The isolation room is supplied and exhausted with a constant volume of air to meet
ventilation, pressurization and thermal requirements. The room’s pressurization is main-
tained by a fixed volumetric offset between the supply and exhaust air volumes. A local
pressure monitor provides visual confirmation of status and audible and visual alarms if
the room pressure is not as desired.
Sequence of Operation
Individual constant volume air valves maintain the supply airflow into the room and the
exhaust airflow out of the room. A fixed constant volume offset is maintained by setting
the exhaust air volume greater than the supply volume. The offset produces negative
pressure in the isolation room relative to the corridor.
A room pressure monitor is installed next to the door entering the isolation room. A
pneumatic room sensor and a reference sensor in the adjoining space provide direct
measurement of pressure. A green status light indicates that the room is negatively
pressured or “normal.” A red light and audible alarm sounds upon an unspecified loss of
pressurization. A mute button silences the audible portion of the alarm. As an additional
optional feature, the third light signals “caution,” indicating that the pressure drop across
the constant volume valves is not being maintained. An adjustable alarm delay prevents
nuisance alarms caused by opening the door. The monitor displays room pressurization
to 0.0001 inches of water gauge (0.0249 Pa).

Phoenix Controls Health Care Facility Design Resource 9

 Fail-safe Condition
Since constant volume valves require neither pneumatic air nor power, a fail-safe condi-
tion does not apply to this application. This room is always in an infectious containment
mode.

Figure 3-1. An example of an

infectious isolation
General Exhaust/Return Air
environment without an
anteroom. HEPA

CVV P

220
280

Room
HEPA
Sensor

20

24 VAC
3C P
CVV

Offset
80
Reference
2C 2C Active Sensor
Pressure Supply Air
Monitor

4-20 mA/0-10 volts

BMS

LEGEND
NOTES:
P Factory Installed Pressure Switch
1. Refer to Room Schedule Sheet (RSS).
CVV Constant Volume Valve 2. Valves are shown horizontally for diagrammatical
purposes only. Actual valve orientation must be
BMS Building Management System
specified for each application.
Field Installed Pneumatics 3. Depending on the form of isolation, ventilation
Cable by Others
design or jurisdiction, HEPA filtration may or
may not be required.
Reheat Valve

Protective Environment without an Anteroom

The isolation room is supplied and exhausted with a constant volume of air to meet
ventilation, pressurization and thermal requirements. The room’s pressurization is main-
tained by a fixed volumetric offset between the supply and exhaust air volumes. A local
pressure monitor provides visual confirmation of status and audible and visual alarms if
the room pressure is not as desired.
Sequence of Operation
Individual constant volume air valves maintains the supply airflow into the room and the
exhaust airflow out of the room. A fixed constant volume offset is maintained by setting
the supply air volume greater than the exhaust air volume. The offset produces a posi-
tive pressure in the isolation room relative to the corridor.

10 Phoenix Controls Health Care Facility Design Resource

A room pressure monitor is installed next to the door entering the isolation room. A
pneumatic room sensor and reference sensor in the adjoining space provide direct
measurement of pressure. A green status light indicates that the room is positively
pressurized or “normal.” A red light and audible alarm sounds upon an unspecified loss of
pressurization. A mute button silences the audible portion of the alarm. As an additional
optional feature, the third light signals “caution,” indicating that the pressure drop across
the constant volume valves is not being maintained. An adjustable alarm delay prevents
nuisance alarms caused by opening the door. The monitor displays the room pressuriza-
tion to 0.0001 inches of water gauge (0.0249 Pa).
Fail-safe Condition
Since constant volume valves require neither pneumatic air nor power, a fail-safe condi-
tion does not apply to this application. This room is always in a protective containment
mode.

Figure 3-2. An example of a

protective environment
General Exhaust/Return Air without an anteroom.
HEPA

CVV P

Airflow Control
Solutions
200
100
HEPA
Room
Sensor

30

24 VAC
3C P
CVV

Offset
70
Reference
2C 2C Active Sensor Supply Air
Pressure
Monitor

4-20 mA/0-10 volts

BMS

LEGEND NOTES:
1. Refer to Room Schedule Sheet (RSS).
P Factory Installed Pressure Switch 2. Valves are shown horizontally for diagrammatical
purposes only. Actual valve orientation must be
CVV Constant Volume Valve
specified for each application.
BMS Building Management System 3. Depending on the form of isolation, ventilation
design or jurisdiction, HEPA filtration may or
Field Installed Pneumatics
may not be required.
Cable by Others
Reheat Valve

Phoenix Controls Health Care Facility Design Resource 11

 Infectious Isolation Environment with an
Anteroom Negative to the Corridor
The patient room and anteroom (also known collectively as the isolation room) are
supplied and exhausted with a constant volume of air to meet ventilation, pressurization
and thermal requirements. The room’s pressurization is maintained by a fixed volumet-
ric offset between the supply and exhaust air volumes. A local pressure monitor provides
visual confirmation of patient room status and audible and visual alarms if the room
pressure is not as desired.
Sequence of Operation
Individual constant volume air valves maintain the supply airflow into the patient room
and the anteroom. Individual constant volume air valves maintain the exhaust airflow
out of the patient room and anteroom.
A fixed constant volume offset in the patient room is maintained by setting the exhaust
air volume greater than the supply air volume. The offset produces a negative pressure
in the patient room relative to the anteroom.
A fixed constant volume offset in the anteroom is maintained by setting the exhaust air
volume equal to the supply air volume. The offset makes the anteroom positive to the
patient room and negative to the corridor.
A room pressure monitor is installed next to the door entering the anteroom. A pneu-
matic patient room sensor and a reference sensor in the anteroom provide direct mea-
surement of pressure. A green status light indicates that the patient room is negatively
pressurized or “normal.” A red light and audible alarm sounds upon an unspecified loss of
pressurization. A mute button silences the audible portion of the alarm. As an additional
optional feature, the third light signals “caution,” indicating that the pressure drop across
the constant volume valves is not being maintained. An adjustable alarm delay will
prevent nuisance alarms caused by opening the door. The monitor displays the room
pressurization to 0.0001 inches of water gauge (0.0249 Pa).
Fail-safe condition
Since constant volume valves require neither pneumatic air nor power, a fail-safe condi-
tion does not apply to this application. This room is always in a protective containment
mode.

12 Phoenix Controls Health Care Facility Design Resource

 Figure 3-3. An example of an
infectious isolation
General Exhaust/Return Air environment with an
anteroom negative to the
HEPA
corridor.

CVV P

CVV
220 P

Room Offset 2C
Sensor 80

Reference
50 Sensor
H CVV
E
P
P A 50 50 P
CVV
24 VAC
3C HEPA

3C Offset
80

2C Active 2C
Pressure Reference Sensor Supply Air
Monitor
2C
2C
4-20 mA/0-10 volts
BMS

Airflow Control
NOTES:
LEGEND 1. Refer to Room Schedule Sheet (RSS).

Solutions
2. Valves are shown horizontally for diagrammatical
P Factory Installed Pressure Switch purposes only. Actual valve orientation must be
CVV Constant Volume Valve specified for each application.
3. Depending on the form of isolation, ventilation
BMS Building Management System design or jurisdiction, HEPA filtration may or
Field Installed Pneumatics may not be required.
4. In this example, the anteroom is positive to the
Cable by Others patient room and negative to the corridor.
Reheat Valve 5. Valves in the anteroom are used for maintaining
ventilation and proper pressurization in lieu of
balancing dampers.

Protective Environment with Airborne

Infectious Isolation
(anteroom is positive to patient room and corridor)
The patient room and anterooms are supplied and exhausted with a constant volume of
air to meet the ventilation, pressurization and thermal requirements. Each room’s pres-
surization is maintained by a fixed volumetric offset between the supply and exhaust air
volumes. A local pressure monitor provides visual confirmation of patient room status
and audible and visual alarms if the room pressure is not as desired.
Sequence of Operation
Individual constant volume air valves maintain the supply airflow into the patient room
and the anteroom. Individual constant volume air valves maintain the exhaust airflow
out of the patient room and anteroom.

Phoenix Controls Health Care Facility Design Resource 13

 A fixed constant volume offset in the patient room is maintained by setting the exhaust
air volume greater than the supply air volume. The offset produces a negative pressure
in the patient room relative to the anteroom.
A fixed constant volume offset in the anteroom is maintained by setting the supply air
volume greater than the exhaust air volume. The offset makes the anteroom positive to
the patient room and positive to the corridor.
A room pressure monitor is installed next to the door entering the anteroom. A pneu-
matic patient room sensor and a reference sensor in the anteroom provide direct mea-
surement of pressure. A green status light indicates that the patient room is negatively
pressurized or “normal.” A red light and audible alarm sounds upon an unspecified loss of
pressurization. A mute button silences the audible portion of the alarm. As an additional
optional feature, the third light signals “caution,” indicating that the pressure drop across
the constant volume valves is not being maintained. An adjustable alarm delay prevents
nuisance alarms caused by opening the door. The monitor displays the room pressuriza-
tion to 0.0001 inches of water gauge (0.0249 Pa).
Fail-safe Condition
Since constant volume valves require neither pneumatic air nor power, a fail-safe condi-
tion does not apply to this application. The patient room is always in protective contain-
ment mode with the anteroom positive to the corridor.

Figure 3-4. An example of a

protective environment with
General Exhaust/Return Air
airborne infectious isolation, in
which the pressure of the HEPA

anteroom is positive to the

patient room and the corridor.
CVV P

CVV
220 P

Room Offset 2C
Sensor 80

50
H CVV
E
P
P A 50 210 P
CVV
HEPA
Reference
Sensor
Offset
80

2C Active 2C
Pressure Supply Air
24 VAC
Monitor
2C
2C
4-20 mA/0-10 volts
BMS

NOTES:
LEGEND 1. Refer to Room Schedule Sheet (RSS).
2. Valves are shown horizontally for diagrammatical
P Factory Installed Pressure Switch purposes only. Actual valve orientation must be
CVV Constant Volume Valve specified for each application.
3. Depending on the form of isolation, ventilation
BMS Building Management System design or jurisdiction, HEPA filtration may or
Field Installed Pneumatics may not be required.
4. In this example, the anteroom is positive to the
Cable by Others patient room and positive to the corridor.
Reheat Valve 5. Valves in the anteroom are used for maintaining
ventilation and proper pressurization in lieu of
balancing dampers.

14 Phoenix Controls Health Care Facility Design Resource

Protective Environment with Airborne Infectious
Isolation
(anteroom is negative to patient room and corridor)
The isolation room is supplied and exhausted with a constant volume of air to meet the
ventilation, pressurization and thermal requirements. The room’s pressurization is main-
tained by a fixed volumetric offset between the supply and exhaust air volumes. A local
pressure monitor provides visual confirmation of status and audible and visual alarms if the
room pressure is not as desired.
Sequence of Operation
Individual constant volume air valves maintain the supply airflow into the room and the
exhaust airflow out of the room. A fixed constant volume offset is maintained by setting the
supply air volume greater than the exhaust air volume. The offset produces a positive
pressure in the isolation room relative to the anteroom.
A fixed constant volume offset in the anteroom is maintained by setting the exhaust air
volume equal to the supply air volume, plus the offset air volume from the patient room
and the corridor. The offset makes the anteroom negative to the patient room and negative
to the corridor.
A room pressure monitor is installed next to the door entering the anteroom. A pneumatic

Airflow Control
room sensor in the patient room and a reference sensor in the anteroom provide direct

Solutions
measurement of pressure. A green status light indicates that the patient room is positively
pressurized or “normal.” A red light and audible alarm sounds upon an unspecified loss of
pressurization. A mute button silences the audible portion of the alarm. As an additional
optional feature, the third light signals “caution,” indicating that the pressure drop across
the constant volume valves is not being maintained. An adjustable alarm delay prevents
nuisance alarms caused by opening the door. The monitor displays the room pressurization
to 0.0001 inches of water gauge (0.0249 Pa).
Fail-safe Condition
Since constant volume valves require neither pneumatic air nor power, a fail-safe condition
does not apply to this application. The patient room is always in a protective containment
mode.

Phoenix Controls Health Care Facility Design Resource 15

Figure 3-5. An example of a
protective environment with
General Exhaust/Return Air
airborne infectious isolation, in
which the pressure of the CVV P

anteroom is negative to the

patient room and the corridor.
HEPA

CVV
200 P

70

Room Offset 2C
Sensor 80

50
H CVV
E
P
P A 210 50 P
CVV
24 VAC
3C HEPA

3C Offset
80

2C Active 2C
Pressure Reference Sensor Supply Air
Monitor
2C
2C
4-20 mA/0-10 volts
BMS

NOTES:
LEGEND 1. Refer to Room Schedule Sheet (RSS).
2. Valves are shown horizontally for diagrammatical
P Factory Installed Pressure Switch purposes only. Actual valve orientation must be
CVV Constant Volume Valve specified for each application.
3. Depending on the form of isolation, ventilation
BMS Building Management System design or jurisdiction, HEPA filtration may or
Field Installed Pneumatics may not be required.
4. In this example, the anteroom is positive to the
Cable by Others
patient room and negative to the corridor.
Reheat Valve 5. Valves in the anteroom are used for maintaining
ventilation and proper pressurization in lieu of
balancing dampers.

16 Phoenix Controls Health Care Facility Design Resource

 Table of Contents
This chapter provides information on the features • Airflow Control Valve Operation, 17
and performance of Phoenix Controls products • Active Pressure Monitor, 21
that are used in health care applications. These
components are engineered to deliver reliable,
effective airflow control.

System Components

Airflow Control Valve Operation

The Phoenix Controls Accel II venturi valves combine a mechanical pressure indepen-
dent regulator with a high-speed position/airflow controller to meet the unique require-
ments of vivarium airflow. These valves can be used in constant volume and two-state
applications.
Pressure Independence
All Phoenix Controls valves maintain a fixed flow of air by adjusting to changes in static
pressure. Each valve has a cone assembly with an internal stainless steel spring. The
custom engineered springs were selected based on passing one million cycles of full-
deflection testing. The cone assembly adjusts the open area of the venturi to system
pressure as described below so that the flow set point is maintained continuously and
instantaneously.
Figure 4-1. The effects of low
static pressure on a venturi
valve cone. When there is low 1" wc
static pressure, less force is (250 Pa)
applied to the cone, which
causes the spring inside to
expand and pull the cone away
from the venturi. The
combination of low pressure

System Components
and a large open area provides
the desired flow.

Figure 4-2. The effects of high

static pressure on a venturi
valve cone. As static pressure
increases force on the cone, the 3" wc
(750 Pa)
spring compresses and the cone
moves into the venturi,
reducing the open area. Higher
pressure and the smaller
opening combine to maintain
flow set point.

Phoenix Controls Health Care Facility Design Resource 17

 Valve Types
With the internal pressure independent cone assembly in operation, airflow can be
regulated by positioning the shaft/cone assembly. The following types of Accel II valves
are available:
• Constant Volume: The valve’s Pivot arm locked Position at
high pressure
shaft is locked into a specific
position, which provides the
scheduled airflow via factory
calibration.
Position at
low pressure

Valve Construction
Applications require that each valve be built to withstand unique environments. The
Accel II valves are available in the following construction types:
• Class A: Non-corrosive atmosphere—supply air, return air, and many general exhaust
applications
• Class B: Corrosive environments—corrosive gaseous decontamination agents

Constant Volume Boxes Compared to Phoenix Constant Volume Valves

A popular approach for controlling isolation rooms uses single do not require rebalancing, recalibration, cleaning, emergency power
blade dampers with pitot tubes, orifice plates or other flow or or straight runs of duct for proper operation. Ventilation control
pressure measuring devices wired to a terminal unit control mod- components that solve these problems justify additional investment,
ule. These are most commonly known as constant volume boxes or especially when research costs and future operating costs are fac-
terminal boxes, and may be chosen because of first costs. Unfortu- tored into the value of the system.
nately, boxes lack the advantages of other flow control devices that
Functionality Constant Volume Boxes Phoenix Controls Valves
Balancing Require adjustment, more costly Factory set, saves time
Rebalancing/recalibration Required periodically None required
Regularly scheduled maintenance Require preventative maintenance None required
Particles in airstream Measuring devices require cleaning Not affected by typical conditions
Straight duct 2-3 duct widths up and downstream None required up or downstream
Auto-zeroing Room goes temporarily out of control Not part of control sequence
Turndown ratio (max:min) 3-3.5:1 Approximately 20:1
Accuracy 15% of command at low end of range 5% of command
Emergency power Requires emergency power Auto-fails to correct flow w/out power
BMS data points BMS controller integral with box Points via room or building network

18 Phoenix Controls Health Care Facility Design Resource

Accel® II Valve (analog)
The Phoenix Controls Accel II Venturi Valves combine a mechanical, pressure-indepen- ®
Phoenix Accel II Venturi Valve

dent regulator with a high-speed position/airflow controller to meet the unique require-

ACTUATOR

T
COVER TAB
DO NOT BLOCK
Access required after installation

20 PSI
END VIEW Phoenix Controls
Corporation

ments of airflow control. These valves can be used in constant volume, two-position, or
Newton, MA 02158 USA
PATENT NOS. 5,304,093 / 5,251,665 AND PATENTS PENDING

VAV applications—all designed to maximize flow performance while reducing related

noise. Valves for VAV applications may be either electrically or pneumatically actuated.
• Pressure-independent operation: All valve types include an immediate response mechanical assembly to maintain
airflow set point as duct static pressure varies.
• Airflow control: By positioning the flow rate controller assembly, the airflow can be adjusted.
Accel II valves are available in:
• Constant volume (CVV series) for maintaining an airflow set point under variable static pressure conditions
• Two-position (PEV/PSV series) for high/low flow control (pneumatic only)
• Base upgradeable (BEV/BSV series) for pneumatic or fixed flow control with feedback option and upgradeability to
VAV (pneumatic only)
• VAV (EXV/MAV series) with VAV closed-loop feedback control (pneumatic or electric)

Specifications
Construction • Compressor sizing: Accel II valves are not continuous air-consuming
• 16 ga. spun aluminum valve body with continuous welded seam devices. For compressor sizing, use:
• Valve bodies available as uncoated aluminum or with corrosion- • single and dual valves: 10 scim
resistant baked phenolic coatings • triple and quad valves: 20 scim
• Composite Teflon® shaft bearings Electric Actuation:
• Spring grade stainless steel spring and PPS slider assembly • 24 Vac (±15%) @60Hz
• Supply valves* insulated with 3/8" (9.5 mm) flexible closed-cell • single and dual valves: 48 VA
polyethylene. Flame/smoke rating 25/50. Density is 2.0 lb/ft3 (32.0 • triple and quad valves: 96 VA
kg/m 3).
Operating Range
• 32-125° F (0-50° C) ambient * Not applicable to CVV series.
• 10-90% non-condensing RH
Teflon is a registered trademark of DuPont Co.
Sound
Designed for low sound power levels to meet
or exceed ASHRAE noise guidelines.
Constant
Performance Feature/Option Volume Two-position Upgradeable VAV VAV
• Pressure independent over a 0.6"-3.0" wc (CVV) (PEV/PSV) (BEV/BSV) (EXV/MAV) (EXV/MAV)
(150-750 Pa) drop across valve

System Components
• Volume control accurate to ±5% of airflow
command signal C P B A A
• No additional straight duct runs needed before or Control type Constant Pneumatic Base Analog Analog
after valve Volume Upgradeable
• Available in flows from 35-6000 cfm Actuator type Fixed Pneumatic Pneumatic Pneumatic Electric
(60-10,000 m3/hr) or Fixed
• Response time to change in command signal:
<1 second Flow feedback signal — — Option 9 9
• Response time to change in duct static pressure: Failsafe Fixed NO/NC NO/NC NO/NC NO/NC or
<1 second Last Posit.
VAV Controller Factory-insulated
Controller Power: valve body (supply) Option 9 9 9 9
• ±15 Vdc @ 0.145 amp (pneumatic only) Field-adjustable flow 9 9 9 9 9
• 0-10 Vdc command signal
• 0-10 Vdc flow feedback signal Flow alarm via
• 0-10 Vdc alarm signal feedback circuit — — — 9 9
Pneumatic Actuation: Flow alarm via
• Only applicable to PEV, PSV, BEV/BSV and EXV/ pressure switch Option Option Option Option Option
MAV-N (pneumatic control type) Low-noise diffuser
• 20 psi (-0/+2 psi) with a 20 micron filter main air construction† 9 9 9 9 9
required (except for CVV)
All valves include pressure independent controllers, factory-calibrated position controllers, and are
available in flows from 35-6000 cfm (60-10,000 m 3/hr).
†Accel II valves are designed to reduce sound over all frequencies, but significantly target the lower bands
(125-500 Hz) to help eliminate the need for silencers.

Phoenix Controls Health Care Facility Design Resource 19

 Valve Sizes, Dimensions and Operating Ranges
Accel II analog valves are available in three specific model sizes: 8, 10 and 12. (For actual
dimensions, refer to the chart below.) In order to increase flow capacity, multiple valves
may be assembled to operate as a unit.

Single (Exhaust Dual (Pneumatic

Valve shown) Supply Valve shown)
®
Phoenix Accel
Acce l I I Venturi
enturi Valve
ACTUATOR

COVER TAB
DO NOT BLOCK
Access required after installation

D E
20 PSI

END VIEW Phoenix Controls

Corporation
Newton, MA 02158 USA
PATENT NOS. 5,304,093 / 5,251,665 AND PATENTS PENDING

E
B
B

C F C A
F

Triple Quad
(Make-up Air (Constant Volume
Valve shown) Valve shown)
G
E B
D
D
B

A
A
F C F C

Valve Dimensions (NO) (NC) (NO) (NC)

A* B* C D E** E F G A* B* C D E** E F G
inches inches inches inches inches inches inches inches mm mm mm mm mm mm mm mm

8 — 7.88 23.50 — 14.00 13.00 28.00 10.13 — 200 597 — 356 330 711 260
10 — 9.88 21.75 — 16.50 15.00 26.00 11.00 — 251 552 — 420 381 660 279
12 — 11.88 26.81 — 18.50 17.00 32.50 12.13 — 302 681 — 470 432 826 308
2-10 20.13 10.13 24.75 1.50 16.50 16.50 28.38 — 511 257 629 38 420 420 721 —
2-12 24.13 12.13 29.81 1.50 18.00 18.00 35.00 — 613 308 757 38 457 457 889 —
3-12 36.38 12.13 29.81 1.50 18.00 18.00 35.00 36.63 924 308 757 38 457 457 889 930
4-12 48.50 12.13 29.81 1.50 18.00 18.00 35.00 — 1232 308 757 38 457 457 889 —
* outer dimension ** maximum of all valve types (some configurations may be smaller)

Operating Ranges
Flow (cfm) Flow (m 3/h) Flow (l/s)
0.6"-3.0" wc 150-750 Pa 150-750 Pa

8 35-700 60-1175 17-330

10 50-1000 85-1700 24-472
12 90-1500 150-2500 43-708
2-10 100-2000 170-3350 47-943
2-12 180-3000 300-5000 85-1415
3-12 270-4500 450-7500 127-2123
4-12 360-6000 600-10000 170-2831

20 Phoenix Controls Health Care Facility Design Resource

Active Pressure Monitor
The Phoenix Controls Active Pressure Monitor accurately measures the pressure differential between two rooms or
spaces in a building where pressurization is critical. Utilizing true differential pressure sensing, it is capable of measur-
ing and alarming to within 0.5% of full scale and display-
ing the pressure to 0.0001 inches of water gauge (0.0249
Pa). It can meet the stringent requirements of labora- Active Pressure Monitor
tory animal facilities, hospital areas, research facility Pressure Status

laboratories and clean rooms. Normal

Alarm
Flow Status
Caution
Each Active Pressure Monitor consists of a room sen- Audible Alarm
Inches of Water Column

sor, a reference space sensor and a room pressure moni-

tor panel. Mute

Optional features include the ability to remotely switch

the room pressure alarm setpoint from a dry contact
and to provide flow alarming when used with Phoenix Phoenix Controls
Corporation

Controls Accel® airflow control valves, verifying both

pressure and volumetric flow requirements are being
met.
Feature/Option APM APM100-
100 REM
Specifications
Dimensions Alarm Output Faceplates
Faceplate SPDT relay Digital Display 9 9
9.5" (241.3 mm) W x 5.5" Contact UL/CSA Rating
(139.7 mm) H 2.0 A @ 30 V AC/DC
Pressure Alarm Status LEDs 9 9
Accuracy Alarm Dead Band Audible Alarm 9 9
• ±0.5% FS Terminal Point 0.1% FS
• (±0.35% FS BFSL) Mute Button 9 9
Alarm Delay Range
Stability 0-30 seconds Flow Caution LED 9
< ±1.0% FS per year
Power Monitoring
Temperature Effects 22-26 VAC
< ±0.03% FS/°F (.05% FS/°C) 50/60 Hz Analog Output (4-20 mA or 0-10 Vdc) 9 9
Over-pressure Power Consumption SPDT alarm relay 9 9
5 PSIG Proof (34.5 KPa) 4.0 VA
Control

System Components
Response Operating Temperature
< 0.25 seconds for full span 32-160° F (0-70° C) Adjustable alarm time delay (0-30 seconds) 9 9
input
Storage Temperature Field reversible pressurization alarm 9 9
Standard Range -40-180° F (-40-82° C)
±0.05" wc (±12.5 Pa) Remote reversible pressurization alarm 9
Weight
Optional Ranges 2.1 pounds (0.95 Kg) Remote flow alarm input 9
±0.1" wc (±25 Pa)
±0.2" wc (±50 Pa)
±0.5" wc (±125 Pa)
±1.0" wc (±250 Pa)
±2.0" wc (±500 Pa)
±5.0" wc (±1250 Pa)
Display
4 digit LED
0.5" height
Analog Output
Field selectable: 4-20 mA, 12
mA at zero pressure
or
0-10 Vdc, 5 Vdc at zero
pressure

Phoenix Controls Health Care Facility Design Resource 21

Applications
The Active Pressure Monitor may be applied in many ways. Two examples are given below:

1. Constant Volume Room

Phoenix Controls’ pressure independent
BMS
valves maintain a constant supply and
exhaust airflow. As a result, room volu-
metric offset remains constant. Pres- Alarm AO
Contact
sure is monitored between the critical
space and a relevant reference space. Active
Pressure
Room
Monitor
Sensor
Local differential pressure alarming is
based on a field configured pressure Reference
Sensor
setpoint. A form C relay is available for
remote alarm monitoring and an ana-
log output is available for monitoring
differential pressure remotely.

24 VAC
Power

Fig. 1. Constant volume room application.

2. Switched Constant Volume with Flow

Alarm Input BMS

Pressure independent valves maintain

a constant supply and exhaust airflow. DPDT Two Position BEV
Relay*
One of these valves is constant volume with '1' Option Solenoid
and the other must be a two-position
valve. A dry contact, supplied by oth- Flow Alarm
ers, triggers a DPDT relay, which AO Input

switches the Active Pressure Monitor Active

Pressure
alarm setpoint to the equal and oppo- Alarm Monitor Room
Sensor
site polarity and switches the two-posi- Contact
Reference
tion valve, effectively changing the Sensor

room from positive to negative pres-

surization and alarming or vice versa. Constant
Volume
Phoenix Controls Accel® valves fitted Supply
with pressure switches provide a flow Valve
alarm input to the APM100. In the event Pressure Switch

of either a flow or differential pressure

alarm, a form C relay is available for re- 24 VAC
mote alarm monitoring. An analog out- Power

put is also available for monitoring dif-

ferential pressure remotely.
Fig 2. Switched constant volume with flow alarm input.
* RIB2401D or equivalent—Call Functional Devices, Inc. at (800) 888-5538 for your nearest RIB distributor.

22 Phoenix Controls Health Care Facility Design Resource

 Table of Contents
• Infectious Isolation Rooms, 23 • Room Airflow Patterns, 27
• Protective Environment • Facility Airflow Direction, 28
Rooms, 24 • Room Pressurization, 29
• HVAC Systems, 25 • Filtration, 31
• Air Change Rates, 26 • Sound Levels in Rooms, 33

Standards and Guidelines

This document is a compilation of excerpts from the Centers for Disease Control (CDC), the American Institute of
Architects (AIA), and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The
intent is to provide the owner, engineer, architect, or health care worker an overview of the standards and guidelines
that apply to the design and/or use of modern isolation rooms.
Individuals should consult all relevant local, state or provincial, and national building codes to determine which stan-
dards or guidelines pertain to a particular health care facility.

Infectious Isolation Rooms

CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54259
“TB isolation rooms should be single-patient rooms with special ventilation characteristics appropriate for the pur-
poses of isolation...The primary purposes of TB isolation rooms are to: (a) separate patients who are likely to have
infectious TB from other persons; (b) provide an environment that will allow reduction of the concentration of droplet
nuclei through various engineering methods; and (c) prevent the escape of droplet nuclei from the TB isolation room
and treatment room, thus preventing entry of M. tuberculosis into the corridor and other areas of the facility.”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 22, sections 7.2.C1.,
7.2.C6. and 7.2.C7.
“At least one airborne infection isolation room shall be provided. These rooms may be located within individual nursing
units and used for normal acute care when not required for isolation cases, or they may be grouped as a separate
isolation unit...
“Airborne infection isolation rooms may be used for noninfectious patients when not needed for patients with air-
borne infectious disease...
“Rooms shall have a permanently installed visual mechanism to constantly monitor the pressure status of the room
when occupied by patients with an airborne infectious disease. The mechanism shall continuously monitor the direc-
tion of the airflow.”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 81, table
footnote 18 Standards & Guidelines
“The infectious disease isolation room described in these guidelines is to be used for isolating the airborne spread of
infectious diseases, such as measles, varicella, or tuberculosis. The design of airborne infection isolation (AII) rooms
should include the provision for normal patient care during periods not requiring isolation precautions...Rooms with
reversible airflow provisions for the purpose of switching between protective environment and AII functions are not
acceptable.”

Phoenix Controls Health Care Facility Design Resource 23

2003 ASHRAE HVAC Applications Handbook, p. 7.8
“Infectious Isolation Unit. The infectious isolation room protects the rest of the hospital from patients’ infectious
diseases. Recent multidrug-resistant strains of tuberculosis have increased the importance of pressurization, air change
rates, filtration, and air distribution design in these rooms...Temperatures and humidities should correspond to those
specified for patient rooms...
“Switchable isolation rooms (rooms that can be set to function with either positive or negative pressure) have been
installed in many facilities. AIA (2001) and CDC (1994) have, respectively, prohibited and recommend against this
approach. The two difficulties of this approach are (1) maintaining the mechanical dampers and (2) that it provides a
false sense of security to staff who think that this provision is all that is required to change a room between protective
isolation and infectious isolation, to the exclusion of other sanitizing procedures.”

Protective Environment Rooms

AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 22, section 7.2.C6.
“Airborne infection isolation rooms may be used for noninfectious patients when not needed for patients with air-
borne infectious disease.”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 23, sections 7.2.D.
and 7.2.D6.
“The differentiating factor between protective environment rooms and other patient rooms is the requirement for
positive air pressure relative to adjoining spaces with all supply air passing through HEPA filters with 99.97 percent
efficiency for particles >3 mm in diameter...
“Rooms shall have a permanently installed visual mechanism to constantly monitor the pressure status of the room
when occupied by patients requiring a protective environment. The mechanism shall continuously monitor the direc-
tion of the airflow.”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 80, table
footnote 17
“The protective environment airflow design specifications protect the patient from common environmental airborne
infectious microbes (i.e., Aspergillus spores). These special ventilation areas shall be designed to provide directed
airflow from the cleanest patient care area to less clean areas...If the facility determines that airborne infection isolation
is necessary for protective environment patients, an anteroom should be provided. Rooms with reversible airflow
provisions for the purpose of switching between protective and airborne infection isolation functions are not accept-
able.”
2003 ASHRAE HVAC Applications Handbook, p. 7.8
“Protective Isolation Units. Immunosuppressed patients (including bone marrow or organ transplant, leukemia, burn,
and AIDS patients) are highly susceptible to diseases. Some physicians prefer an isolated laminar airflow unit to protect
the patient; others are of the opinion that the conditions of the laminar cell have a psychologically harmful effect on
the patient and prefer flushing out the room and reducing spores in the air. An air distribution of 15 air changes per
hour supplied through a nonaspirating diffuser is often recommended. With this arrangement, the sterile air is drawn
across the patient and returned near the floor, at or near the door to the room.
“In cases where the patient is immunosuppressed but not contagious, positive pressure should be maintained between
the patient room and adjacent area. Some jurisdictions may require an anteroom, which maintains a negative pressure
relative to the adjacent isolation room and an equal pressure to the corridor, nurses’ station, or common area. Exam
and treatment rooms should be controlled in the same manner. Positive pressure should also be maintained between
the entire unit and adjacent areas to preserve sterile conditions.

24 Phoenix Controls Health Care Facility Design Resource

“When a patient is both immunosuppressed and contagious, isolation rooms within the unit may be designed and
balanced to provide a permanent equal or negative pressure relative to the adjacent area or anteroom. Pressure
controls in the adjacent area or anteroom must maintain the correct pressure relationship relative to the other
adjacent room(s). A separate, dedicated air-handling system to serve the protective isolation unit simplifies pressure
control and quality...”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 23, section 7.2.D.1.
“As designated by the functional program, both airborne infection isolation and protective environment rooms may be
required. Many facilities care for patients with an extreme susceptibility to infection, e.g., immunosuppressed patients
with prolonged granulocytopenia, most notably bone marrow recipients; or solid-organ transplant recipients and
patients with hematological malignancies who are receiving chemotherapy and are severely granulocytopenic. These
rooms are not intended for use with patients diagnosed with HIV infection or AIDS, unless they are also severely
granulocytopenic. Generally, protective environments are not needed in community hospitals, unless these facilities
take care of these types of patients. The appropriate clinical staff should be consulted regarding room type and spatial
needs to meet facility infection control requirements should be incorporated in design programming.”

HVAC Systems
CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54279
“Two types of general ventilation systems can be used for dilution and removal of contaminated air: the single-pass
system and the recirculating system. In a single-pass system, the supply air is either outside air that has been appropri-
ately heated and cooled or air from a central system that supplies a number of areas. After air passes through the room
(or area), 100% of that air is exhausted to the outside. The single-pass system is the preferred choice in areas where
infectious airborne droplet nuclei are known to be present (e.g., TB isolation rooms or treatment rooms) because it
prevents contaminated air from getting recirculated to other areas of the facility.
“In a recirculating system, a small portion of the exhaust air is discharged to the outside and is replaced with fresh
outside air, which mixes with the portion of exhaust air that was not discharged to the outside. The resulting mixture,
which can contain a large proportion of contaminated air, is then recirculated to the areas serviced by the system. This
air mixture could be recirculated into the general ventilation, in which case contaminants may be carried from
contaminated areas to uncontaminated areas. Alternatively, the air mixture could also be recirculated within a specific
room or area, in which case other areas of the facility will not be affected.”
CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54260
“Air from TB isolation rooms and treatment rooms used to treat patients who have known or suspected infectious TB
should be exhausted to the outside in accordance with applicable federal, state and local regulations. The air should not
be recirculated into the general ventilation. In some instances, recirculation of air into the general ventilation system
from such rooms is unavoidable (i.e., in existing facilities in which the ventilation system or facility configuration makes
venting the exhaust to the outside impossible). In such case, HEPA filters should be installed in the exhaust duct leading
from the room to the general ventilation system to remove infectious organisms and particulates the size of droplet
Standards & Guidelines

nuclei from the air before it is returned to the general ventilation system.”
CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54284
“Individual room-air recirculation can be used in areas where there is no general ventilation system, where an existing
system is incapable of providing adequate airflow, or where an increase in ventilation is desired without affecting the
fresh air supply or negative pressure system already in place. Recirculation of HEPA-filtered air within a room can be

Phoenix Controls Health Care Facility Design Resource 25

achieved in several ways: (a) by exhausting air from the room into a duct, filtering it through a HEPA filter installed in
the duct, and returning it to the room...; (b) by filtering air through HEPA recirculation system mounted on the wall or
ceiling of the room...; or (c) by filtering air through portable HEPA recirculation systems.”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, pp. 79-81
Table 7.2 (partial) Ventilation Requirements for Areas Affecting Patient Care in Hospitals and Outpatient Facilities

Recirculated
All air exhausted by means of
directly to outdoors6 room units7
Protective environment room – No
Airborne infection isolation room Yes No
Isolation alcove or anteroom Yes No
6
“Air from areas with contamination and/or odor problems shall be exhausted to the outside and not recirculated to other areas. Note
that individual circumstances may require special consideration for air exhaust to outside, e.g., in intensive care units in which
patients with pulmonary infection are treated, and rooms for burn patients.
7
“Recirculating room HVAC units refers to those local units that are used primarily for heating and cooling of air, and not disinfection
of air. Because of cleaning difficulty and potential for buildup of contamination, recirculating room units shall not be used in areas
marked ‘No.’ However, for airborne infection control, air may be recirculated within individual isolation rooms if HEPA filters are
used. Isolation and intensive care unit rooms may be ventilated by reheat induction units in which only the primary air supplied
from a central system passes through the reheat unit. Gravity-type heating or cooling units such as radiators or convectors shall not
be used in operating rooms and other special care areas.”

2003 ASHRAE HVAC Applications Handbook, pp. 7.4, 7.7

“In critical-care areas, constant volume systems should be used to ensure proper pressure relationships and ventila-
tion. In noncritical patient care areas and staff rooms, variable air volume (VAV) systems may be considered for energy
conservation. When using VAV systems in the hospital, special care should be taken to ensure that minimum ventila-
tion rates (as required by codes) are maintained and that pressure relationships between various departments are
maintained. With VAV systems, a method such as air volume tracking between supply, return, and exhaust could be
used to control pressure relationships...
“Because of the cleaning difficulty and potential for buildup of contamination, recirculating room units must not be
used in areas marked “No.” Note that the standard recirculating room unit may also be impractical for primary control
where exhaust to the outside is required...
“A separate, dedicated air-handling system to serve the protective isolation unit simplifies pressure control and qual-
ity.”
See also Table 3, “Ventilation Requirements for Areas Affecting Patient Care in Hospitals and Outpatient
Facilities,” from the 2003 ASHRAE HVAC Applications Handbook, pp. 7.6-7.7 (reproduced in this
document as Appendix A).

Air Change Rates

CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54287
“To reduce the concentration of droplet nuclei, TB isolation rooms and treatment rooms in existing health-care
facilities should have an airflow of >6 ACH. Where feasible, this airflow rate should be increased to >12 ACH by
adjusting or modifying the ventilation system or by using auxiliary means (e.g., recirculation of air through fixed HEPA
filtration units or portable air cleaners)...New construction or renovation of existing health-care facilities should be
designed so that TB isolation rooms achieve an airflow of >12 ACH.”

26 Phoenix Controls Health Care Facility Design Resource

AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, pp. 79-80
Table 7.2 (partial) Ventilation Requirements for Areas Affecting Patient Care in Hospitals and Outpatient
Facilities

Min. air changes of Min. total air

outdoor air per hour3 changes per hour4, 5
Toilet room – 10
Protective environment room 2 12
Airborne infection isolation room 2 12
Isolation alcove or anteroom – 10
3
“To satisfy exhaust needs, replacement air from the outside is necessary. Table 7.2 does not attempt to describe specific amounts of
outside air to be supplied to individual spaces except for certain areas such as those listed. Distribution of the outside air, added to the
system to balance required exhaust, shall be as required by good engineering practice. Minimum outside air quantities shall remain
constant while the system is in operation.”
4
“Number of air changes may be reduced when the room is unoccupied if provisions are made to ensure that the number of air changes
indicated is reestablished any time the space is being utilized. Adjustments shall include provisions so that the direction of air movement
shall remain the same when the number of air changes is reduced. Areas not indicated as having continuous direction control may have
ventilation systems shut down when space is unoccupied and ventilation is not otherwise needed, if the maximum infiltration or
exfiltration permitted in Note 2* is not exceeded and if adjacent pressure balancing relationships are not compromised. Air quantity
calculations must account for filter loading such that the indicated air change rates are provided up until the time of filter change-out.
5
“Air change requirements indicated are minimum values. Higher values should be used when required to maintain indicated room
conditions (temperature and humidity), based on the cooling load of the space (lights, equipment, people, exterior walls and windows,
etc.).

* Note 2: “Design of the ventilation system shall provide air movement which is generally from clean to less clean areas. If any form of
variable air volume or load shedding system is used for energy conservation, it must not compromise the corridor-to-room pressure
balancing relationships or the minimum air changes required by the table.”

2003 ASHRAE HVAC Applications Handbook, pp. 7.4

“The number of air changes may be reduced to 25% of the indicated value when the room is unoccupied, if provisions
are made to ensure that (1) the number of air changes indicated is reestablished whenever the space is occupied, and
(2) the pressure relationship with the surrounding rooms is maintained when the air changes are reduced.”
See also:
Table 3, “Ventilation Requirements for Areas Affecting Patient Care in Hospitals and Outpatient
Facilities,” from the 2003 ASHRAE HVAC Applications Handbook, pp. 7.6-7.7 (reproduced in this
document as Appendix A).

Room Airflow Patterns

CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care Standards & Guidelines
Facilities, p. 54280
“General ventilation systems should be designed to provide optimal patterns of airflow within rooms and prevent air
stagnation or short-circuiting of air from the supply to the exhaust (i.e., passage of air directly from the air supply to the
air exhaust). To provide optimal airflow patterns, the air supply and exhaust should be located such that clean air first
flows to parts of the room where HCWs (health care workers) are likely to work, and then flows across the infectious
sources and into the exhaust. In this way, the HCW is not positioned between the infectious source and the exhaust
location. Although this configuration may not always be possible, it should be used when feasible. One way to achieve

Phoenix Controls Health Care Facility Design Resource 27

this airflow pattern is to supply air at the side of the room opposite the patient and exhaust it from the side where the
patient is located. Another method, which is most effective when the supply is cooler than the room air, is to supply air
near the ceiling and exhaust it near the floor...Airflow patterns are affected by large air temperature differentials, the
precise location of the supply and exhaust, the location of furniture, the movement of HCWs and patients, and the
physical configuration of the space. Smoke tubes can be used to visualize airflow patterns in a manner similar to that
described for estimating room air mixing.”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 50, section 7.31.D7.
“The bottoms of ventilation (supply/return) openings shall be at least 3 inches (76.2 millimeters) above the floor.”
2003 ASHRAE HVAC Applications Handbook, p. 7.3
“In general, outlets supplying air to sensitive ultraclean areas and highly contaminated areas should be located on the
ceiling, with perimeter or several exhaust outlets should be near the floor. This arrangement provides a downward
movement of clean air through the breathing and working zones to the floor area for exhaust. There are two recognized
approaches to infectious isolation room air distribution. One approach locates the supply air above and near the
doorway, and exhaust air from near the floor behind the patient’s bed. This arrangement has the intent of controlling
the flow of clean air first to parts of the room where workers or visitors are likely to be, and across the infected source
into the exhaust. The limited ability of this arrangement to achieve this directional airflow movement, in view of the
relatively low air exchange rates involved and the minimal influence of the exhaust outlet, led others to advocate a
second arrangement in which the supply diffuser and exhaust outlet are located to maximize room air mixing, and
therefore contaminant removal, typically with ceiling-mounted supply and exhaust outlets over the patient bed or on
the wall behind the bed. With this arrangement, the supply diffusers must be carefully selected and located such that
primary air throw does not induce bedroom air to enter the anteroom.”

Facility Airflow Direction

CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54281
“The general ventilation system should be designed and balanced so that air flows from less contaminated (i.e., more
clean) to more contaminated (less clean) areas...For example, air should flow from corridors (cleaner areas) into TB
isolation rooms (less clean areas) to prevent spread of contaminants to other areas. In some special treatment rooms
in which operative and invasive procedures are performed, the direction of airflow is from the room to the hallway to
provide cleaner air during these procedures. Cough-inducing or aerosol-generating procedures (e.g., bronchoscopy or
irrigating of turberculous abscesses) should not be performed in rooms with this type of airflow on patients who may
have infectious TB...
“The direction of airflow is controlled by creating a lower (negative) pressure in the area into which the flow of air is
desired. For air to flow from one area to another, the air pressure into the two areas must be different. Air will flow from
a higher pressure area to a lower pressure area. The lower pressure area is described as being at negative* pressure
relative to the higher pressure area. Negative pressure is attained by exhausting air from an area at a higher rate than
air is being supplied. The level of negative pressure necessary to achieve the desired airflow will depend on the physical
configuration of the ventilation system and area, including the airflow path and flow openings, and should be deter-
mined on an individual basis by an experienced ventilation engineer.”
* Negative is defined relative to the air pressure in the area from which air is to flow.

2003 ASHRAE HVAC Applications Handbook, p. 7.3

“Because of the dispersal of bacteria resulting from such necessary activities, air-handling systems should provide air
movement patterns that minimize the spread of contamination. Undesirable airflow between rooms and floors is often
difficult to control because of open doors, movement of staff and patients, temperature differentials, and stack effect,
which is accentuated by vertical openings such as chutes, elevator shafts, stairwells, and mechanical shafts common to

28 Phoenix Controls Health Care Facility Design Resource

hospitals. Although some of these factors are beyond practical control, the effect of others may be minimized by
terminating shaft openings in enclosed rooms and by designing and balancing air systems to create positive or negative
air pressure within certain rooms and areas.”
See also Table 7.2 (partial), “Ventilation Requirements for Areas Affecting Patient Care in Hospitals and
Outpatient Facilities,” from AIA Guidelines for Design and Construction of Hospital and Health Care
Facilities, pp. 79-81 (reproduced in this document as Appendix B).

Room Pressurization/Anterooms
CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54281
“The minimum pressure difference necessary to achieve and maintain negative pressure that will result in airflow into
the room is very small (0.001 inch of water). Higher pressures (> 0.001 inch of water) are satisfactory: however, these
higher pressures may be difficult to achieve. The actual level of negative pressure achieved will depend on the difference
in the ventilation exhaust and supply flows and the physical configuration of the room, including the airflow path and
flow opening. If the room is well sealed, negative pressure greater than the minimum of 0.001 inch of water may be
readily achieved. However, if rooms are not well sealed, as may be the case in many facilities (especially older facilities),
achieving higher negative pressures may require exhaust/supply flow differentials beyond the capability of the ventila-
tion system.
“To establish negative pressure in a room that has a normally functioning ventilation system, the room supply and
exhaust airflows are first balanced to achieve an exhaust flow of either 10% or 50 cubic feet per minute (cfm) greater
than supply (whichever is the greater). In most situations, this specification should achieve a negative pressure of at
least 0.001 inch of water. If the minimum of 0.001 is not achieved and cannot be achieved by increasing the flow
differential (within the limits of the ventilation system), the room should be inspected for leakage (e.g., through doors,
windows, plumbing, and equipment wall penetrations), and corrective action should be taken to seal the leaks.
“Negative pressure in a room can be altered by changing the ventilation system operation or by opening and closing the
room’s doors, corridor doors, or windows. When an operating configuration has been established, it is essential that all
doors and windows remain properly closed in the isolation room and other areas (e.g., doors in corridors that affect air
pressure) except when persons need to enter or leave the room area...
“Although an anteroom is not a substitute for negative pressure in a room, it may be used to reduce escape of droplet
nuclei during opening and closing of the isolation room door. Some anterooms have their own air supply duct but
others do not. The TB isolation room should have negative pressure relative to the anteroom, but the air pressure in
the anteroom relative to the corridor may vary depending on the building design. This should be determined, in
accordance with applicable regulation, by a qualified ventilation engineer.”
CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54282
“Differential pressure-sensing devices also can be used to monitor negative pressure; they can provide either periodic
(noncontinuous) pressure measurements or continuous pressure monitoring. The continuous monitoring compo- Standards & Guidelines
nents may simply be a visible and/or audible warning signal that air pressure is low. In addition, it may also provide a
pressure readout signal, which can be recorded for later verification or used to automatically adjust the facility’s
ventilation control system...
“Pressure-measuring devices should sense the room pressure just inside the airflow path into the room (e.g., at the
bottom of the door). Unusual airflow patterns within the room can cause pressure variations; for example, air can be
at negative pressure at the middle of a door and at positive pressure at the bottom of the same door...If the pressure-
sensing ports of the device cannot be located directly across the airflow path, it will be necessary to validate that the
negative pressure at the sensing point is and remains the same as the negative pressure across the flow path.

Phoenix Controls Health Care Facility Design Resource 29

“Pressure-sensing devices should incorporate an audible warning with time delay to indicate that a door is open. When
the door to the room is opened, the negative pressure will decrease. The time-delayed signal should allow sufficient
time for persons to enter or leave the room without activating the audible warning.”
CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54283
“A potential problem with using pressure-sensing devices is that the pressure differentials used to achieve the low
negative pressure necessitates the uses of very sensitive mechanical devices, electronic devices, or pressure gauges to
ensure accurate measurements. Use of devices that cannot measure these low pressures (i.e., pressures as low as 0.001
inch of water) will require setting higher negative pressures that may be difficult and, in some instances, impractical to
achieve...
“Periodic checks are required to ensure that the continuous monitoring devices, if used, are operating properly.”
CDC MMWR, Key Terms section
“Immunocompromised patients are those patients whose immune mechanisms are deficient because of immunologic
disorders (e.g., human immunodeficiency virus [HIV] infection or congenital immune deficiency syndrome), chronic
diseases (e.g., diabetes, cancer, emphysema, or cardiac failure), or immunosuppressive therapy (e.g., radiation, cytotoxic
chemotherapy, anti-rejection medication, or steroids). Immunocompromised patients who are identified as high-risk
patients have the greatest risk of infection caused by airborne or waterborne microorganisms. Patients in this subset
include persons who are severely neutropenic for prolonged periods of time (i.e., an absolute neutrophil count [ANC]
of <500 cells/mL), allogeneic HSCT patients, and those who have received the most intensive chemotherapy (e.g.,
childhood acute myelogenous leukemia patients).”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, pp. 79-80
Table 7.2 (partial) Ventilation Requirements for Areas Affecting Patient Care in Hospitals and Outpatient Facilities

Air movement relationship

to adjacent area2
Toilet room In
Protective environment room Out
Airborne infection isolation room In
Isolation alcove or anteroom In/Out
2
“Design of the ventilation system shall provide air movement which is generally from clean to less clean areas. If any form of variable air
volume or load shedding system is used for energy conservation, it must not compromise the corridor-to-room pressure balancing
relationships or the minimum air changes required by the table.”

AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 23, Appendix
section A7.2.D.
“Immunosuppressed Host Airborne Infection Isolation (Protective Environment/Airborne Infection Isolation). An
anteroom is required for the special case in which an immunosuppressed patient requires airborne infection isola-
tion...There is no prescribed method for anteroom ventilation—the room can be ventilated with either of the following
airflow patterns: (a) airflows from the anteroom, to the patient room and the corridor, or (b) airflows from the patient
room and the corridor, into the anteroom. The advantage of pattern (a) is the provision for a clean anteroom in which
health care workers need not mask before entering the anteroom.”
2003 ASHRAE HVAC Applications Handbook, p. 7.8
“In cases where the patient is immunosuppressed but not contagious, a positive pressure should be maintained
between the patient room and adjacent area. Some jurisdictions may require an anteroom, which maintains a negative
pressure relationship with respect to the adjacent isolation room and an equal pressure to the corridor, nurses’ station,
or common area.

30 Phoenix Controls Health Care Facility Design Resource

“When a patient is both immunosuppressed and contagious, isolation rooms within the unit may be designed and
balanced to provide a permanent equal or negative pressure relationship with respect to the adjacent area or ante-
room. Pressure controls in the adjacent area or anteroom must maintain the correct pressure relationship relative to
the other adjacent room(s). A separate, dedicated air-handling system to serve the protective isolation unit simplifies
pressure control and quality...
“The designer should work closely with health care planners and the code authority to determine the appropriate
isolation room design. It may be desirable to provide more complete control, with a separate anteroom used as an air
lock to minimize the potential that airborne particulates from the patients’ area reach adjacent areas.”
Table 3, “Ventilation Requirements for Areas Affecting Patient Care in Hospitals and Outpatient
Facilities,” from the 2003 ASHRAE HVAC Applications Handbook, pp. 7.6-7.7 (reproduced in this
document as Appendix A).

Filtration
CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care
Facilities, p. 54283
“HEPA filtration can be used as a method of air cleaning that supplements other recommended ventilation measures.
For the purposes of these guidelines, HEPA filters are defined as air-cleaning devices that have a demonstrated and
documented minimum removal efficiency of 99.97% of particles greater than or equal to 0.3 mm (microns) in diameter.
HEPA filters have been shown to be effective in reducing the concentration of Aspergillus spores (which range in size
from 1.5 mm to 6 mm) to below measurable levels (100-102). The ability of HEPA filters to remove tubercle bacilli from
the air has not been studied, but M. tuberculosis droplet nuclei probably range from 1 mm to 5 mm in diameter (i.e.,
approximately the same size as Aspergillus spores). Therefore, HEPA filters can be expected to remove infectious
droplet nuclei from contaminated air. HEPA filters can be used to clean air before it is exhausted to the outside,
recirculated to other areas of a facility, or recirculated within a room. If the device is not completely passive, (e.g., it
utilizes techniques such as electrostatics) and the failure of the electrostatic components permits loss of filtration
efficiency to less than 99.97%, the device should not be used in systems that recirculate air back into the general facility
ventilation system from TB isolation rooms and treatment rooms in which procedures are performed on patients who
may have infectious TB...
“HEPA filters can be used in a number of ways to reduce or eliminate infectious droplet nuclei from room air or exhaust.
These methods include placement of HEPA filters (a) in exhaust ducts to remove droplet nuclei from air being
discharged to the outside, either directly or through ventilation equipment; (b) in ducts discharging room air into the
general ventilation system; and (c) in fixed or portable room-air cleaners. The effectiveness of portable HEPA room-air
cleaning units has not been evaluated adequately, and there is probably considerable variation in their effectiveness.
HEPA filters can also be used in exhaust ducts or vents that discharge air from booths or enclosures into the surround-
ing room...In any application, HEPA filters should be installed carefully and maintained meticulously to ensure adequate
function.”
2003 ASHRAE HVAC Applications Handbook, pp. 7.2-7.3
“All central ventilation or air-conditioning systems should be equipped with filters having efficiencies no lower than
Standards & Guidelines

those indicated in Table 1. Where two filter beds are indicated, Filter Bed No. 1 should be located upstream of the air-
conditioning equipment, and Filter Bed No. 2 should be downstream of the supply fan. Appropriate precautions should
be observed to prevent wetting the filter media by free moisture from humidifiers. Where only one filter bed is
indicated, it should be located upstream of air-conditioning equipment. All filter efficiencies are based on ASHRAE
Standard 52.2.

Phoenix Controls Health Care Facility Design Resource 31

“The following are guidelines for filter installations:
• HEPA filters with Minimum Efficiency Reporting Values (MERV) of 17 should be used on air supplies serving
protective-environment rooms for clinical treatment of patients with a high susceptibility to infection due to
leukemia, burns, bone marrow transplant, organ transplant, or human immunodeficiency virus (HIV). HEPA
filters should also be used on discharge air from fume hoods or safety cabinets in which infectious or highly
radioactive materials are processed. The filter system should be designed and equipped to permit safe removal,
disposal, and replacement of contaminated filters.
• All filters should be installed to prevent leakage between filter segments and between the filter bed and its
supporting frame. A small leak that permits any contaminated air to escape through the filter can destroy the
usefulness of the best air cleaner.
• A manometer should be installed in the filter system to measure pressure drop across each filter bank. Visual
observation is not accurate for determining filter loading.
• High-efficiency filters should be installed in the system, with adequate facilities provided for maintenance
without introducing contamination into the delivery system or the area served.
• Because high-efficiency filters are expensive, the hospital should project the filter bed life and replacement costs
and incorporate these into the operating budget.
• During construction, openings in ductwork and diffusers should be sealed to prevent intrusion of dust, dirt, and
hazardous materials. Such contamination is often permanent and provides a medium for growth of infectious
agents. Existing or new filters may rapidly become contaminated by construction dust...”
Table 1 Filter Efficiencies for Central Ventilation and Air-Conditioning Systems in General Hospitals

Minimum Filter Efficiencies, MERVa

Number of Filter Bed
Filter Beds Area Designation No. 1 No. 2
2 Orthopedic operating room 8 17b
Bone marrow transplant operating room
Organ transplant operating room
2 General procedure operating rooms 8 14
Delivery rooms
Nurseries
Intensive care units
Patient care rooms
Treatment rooms
Diagnostic and related areas
1 Laboratories 13
Sterile storage
1 Food preparation areas 8
Laundries
Administrative areas
Bulk storage
Soiled holding areas
a
BMERV = Minimum Efficiency Reporting Value based on ASHRAE Standard 52.2-1999.
b
HEPA filters at air outlets.

32 Phoenix Controls Health Care Facility Design Resource

AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 70, section 7.31.D8.
“All central ventilation or air conditioning systems shall be equipped with filters with efficiencies equal to, or greater
than, those specified in Table 3. Where two filter beds are required, filter bed no. 1 shall be located upstream of the air
conditioning equipment and filter bed no. 2 shall be downstream of any fan or blowers. Filter efficiencies, tested in
accordance with ASHRAE 52-92, shall be average.”
AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, p. 82
Table 7.3 (partial) Filter Efficiencies for Central Ventilation and Air Conditioning Systems in General Hospitals

No. of Filter bed Filter bed

Area designation filter beds no. 1 (%) no. 2 (%)
All areas for inpatient care, treatment, and diagnosis, 2 30 90
and those areas providing direct service or clean
supplies such as sterile and clean processing, etc.
Protective environment room 2 30 99.97
Laboratories 1 80 –

Sound Levels in Rooms

2003 ASHRAE HVAC Applications Handbook, p. 47.29
“Table 34 lists normally accepted HVAC-related background sound levels appropriate to various types of space-occu-
pancies. Perceived loudness and task interference are factored into the numerical part of the RC rating. The sound-
quality design target is assumed to be a neutral-sounding (N) spectrum, although some spectrum imbalance is prob-
ably tolerable within limits.”
Table 34 (partial) Design Guidelines for HVAC-Related Background Sound in Rooms

Room Types RC(N) (QAI > 5a,b)

Hospitals and clinics (private rooms) 25-35
a
Values and ranges are based on judgment and experience, not on quantitative evaluations of human reactions. They represent general
limits of acceptability for typical building occupancies. Higher or lower values may be appropriate and should be based on a careful
analysis of economics, space usage, and user needs.
b
When the quality of sound in the space is important, specify criteria in terms of RC(N). If the quality of sound in the space is
secondary concern, the criteria may be specified in terms of NC levels of similar magnitude.

Standards & Guidelines

Phoenix Controls Health Care Facility Design Resource 33

34 Phoenix Controls Health Care Facility Design Resource
 Appendix A: Ventilation Requirements for Areas Affecting
Patient Care in Hospitals and Outpatient Facilities
(Table 3 from 2003 ASHRAE Applications Handbook, pp. 7.6-7.7)

Pressure Minimum Air Minimum All Air Air

Relationship Changes of Total Air Exhausted Recirculated Relative
to Adjacent Outside Air Changes per Directly to Within Room Humidity,n Temperature, o
Function Space Areasa per Hourb Hourc Outside m Unitsd % ºC
Surgery and Critical Care
Operating room (recirculating air system) Positive 5 25 – No 45 to 55 17 to 27
Operating/surgical cystoscopic roomse, p, q Positive 5 25 – No 45 to 55 20 to 23r
Delivery room p Positive 5 25 – No 45 to 55 20 to 23
Recovery roomp * 2 6 – No 45 to 55 24 ± 1
Critical and intensive care * 2 6 – No 30 to 60 21 to 24
Newborn intensive care * 2 6 – No 30 to 60 22 to 26
Treatment room s * – 6 – – 30 to 60 24
Nursery suite Positive 5 12 – No 30 to 60 24 to 27
Trauma roomf, s Positive 5 12 – No 45 to 55 17 to 27
Anesthesia gas storage Negative – 8 Yes – – –
GI Endoscopy Negative 2 6 – No 30 to 60 20 to 23
Bronchoscopy q Negative 2 12 Yes No 30 to 60 20 to 23
Emergency waiting rooms Negative 2 12 Yes – 30 to 60 23 ± 1
Triage Negative 2 12 Yes – – 21 to 24
Radiology waiting rooms Negative 2 12 Yest, u – – 21 to 24
Nursing
Patient room * 2 6v – – 30 (W), 50 (S) 24 ± 1
Toilet roomg Negative Optional 10 Yes No – –
Newborn nursery suite * 2 6 – No 30 to 60 22 to 26
Protective environment roomi, q, w Positive 2 12 – No – 24
Airborne infection isolation roomh, q, x Negative 2 12 Yesu No – 24
Isolation alcove or anteroom w, x Pos./Neg. 2 10 Yes No – –
Labor/delivery/recovery/postpartum (LDRP) * 2 6v – – 30 (W), 50 (S) 24 ± 1
Public corridor Negative 2 2 – – – –
Patient corridor * 2 4 – – – –
Ancillary
Radiologyy
X-ray (diagnostic and treatment) * 2 6 – – 40 (W), 50 (S) 26 to 27
X-ray (surgery/critical care, catheterization) Positive 3 15 – No 30 to 60 21 to 24
Darkroom Negative 2 10 Yesj No – –
Laboratory, generaly Negative 2 6 Yes No 30 to 60 23 ± 1
Laboratory, bacteriology Negative 2 6 Yes No 30 to 60 23 ± 1
Laboratory, biochemistry y Positive 2 6 – No 30 to 60 23 ± 1
Laboratory, cytology Negative 2 6 Yes No 30 to 60 23 ± 1
Laboratory, glasswashing Negative Optional 10 Yes – – –
Laboratory, histology Negative 2 6 Yes No 30 to 60 23 ± 1
Microbiologyy Negative – 6 Yes No 30 to 60 23 ± 1
Laboratory, nuclear medicine Negative 2 6 Yes No 30 to 60 23 ± 1
Laboratory, pathology Negative 2 6 Yes No 30 to 60 23 ± 1
Laboratory, serology Positive 2 6 Yes No 30 to 60 23 ± 1
Laboratory, sterilizing Negative Optional 10 Yes No 30 to 60 23 ± 1
Laboratory, media transfer Positive 2 4 – No 30 to 60 23 ± 1
Autopsy room q Negative 2 12 Yes No – –
Nonrefrigerated body-holding roomk Negative Optional 10 Yes No – 21
Pharmacy Positive 2 4 – – 30 to 60 23 ± 1
Administration
Admitting and waiting rooms Negative 2 6 Yes – 30 to 60 23 ± 1

Phoenix Controls Health Care Facility Design Resource 35

 Appendix A: Ventilation Requirements for Areas Affecting
Patient Care in Hospitals and Outpatient Facilities (continued)
Pressure Minimum Air Minimum All Air Air
Relationship Changes of Total Air Exhausted Recirculated Relative
to Adjacent Outside Air Changes per Directly to Within Room Humidity,n Temperature, o
Function Space Areasa per Hourb Hourc Outside m Unitsd % ºC
Diagnostic and Treatment
Bronchoscopy, sputum collection, and Negative 2 12 Yes – 30 to 60 23 ± 1
pentamidine administration
Examination room * 2 6 – – 30 to 60 23 ± 1
Medication room Positive 2 4 – – 30 to 60 23 ± 1
Treatment room * 2 6 – – 30 (W), 50 (S) 23 ± 1
Physical therapy and hydrotherapy Negative 2 6 – – 30 to 60 22 to 26/27
Soiled workroom or soiled holding Negative 2 10 Yes No 30 to 60 22 to 26
Clean workroom or clean holding Positive 2 4 – – – –
Sterilizing and Supply
ETO-sterilizer room Negative – 10 Yes No 30 to 60 22 to 26
Sterilizer equipment room Negative – 10 Yes No 30 to 60 23 ± 1
Central medical and surgical supply
Soiled or decontamination room Negative 2 6 Yes No 30 to 60 22 to 26
Clean workroom Positive 2 4 – No 30 to 60 22 to 26
Sterile storage Positive 2 4 – – Under 50 23 ± 1
Service
Food preparation centerl * 2 10 Yes No – –
Warewashing Negative Optional 10 Yes No – –
Dietary day storage • Optional 2 – No – –
Laundry, general Negative 2 10 Yes No – –
Soiled linen sorting and storage Negative Optional 10 Yes No – –
Clean linen storage Positive 2 (Optional) 2 – – – –
Linen and trash chute room Negative Optional 10 Yes No – –
Bedpan room Negative Optional 10 Yes No – –
Bathroom Negative Optional 10 Yes No – 22 to 26
Janitor’s closet Negative Optional 10 Yes No – –
(W) = winter (S) = summer * = Continuous directional control not required

a
Where continuous direction control is not required, variations should be minimized; in no case should a lack of directional control allow spread of
infection from one area to another. Boundaries between functional areas (wards or departments) should have directional control. Lewis (1998) describes
ways to maintain directional control by applying air-tracking controls. Ventilation system design should provide air movement, generally from clean to
less clean areas. If any VAV or load-shedding system is used for energy conservation, it must not compromise pressure-balancing relationships or
minimum air changes required by the table. See note z for additional information.
b
Ventilation rates in this table cover ventilation for comfort, as well as for asepsis and odor control in areas of acute-care hospitals that directly affect
patient care. Ventilation rates in accordance with ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality, should be used for areas for which
specific ventilation rates are not given. Where a higher outside air requirement is called for in Standard 62 than here, use the higher value.
c
Total air changes indicated should be either supplied or, where required, exhausted. Number of air changes can be reduced when the room is unoccu-
pied, if the pressure relationship is maintained and the number of air changes indicated is reestablished any time the space is used. Air changes shown are
minimum values. Higher values should be used when required to maintain room temperature and humidity conditions based on the cooling load of the
space (lights, equipment, people, exterior walls and windows, etc.).
d
Recirculating HEPA filter units used for infection control (without heating or cooling coils) are acceptable. Gravity-type heating or cooling units such as
radiators or convectors should not be used in operating rooms and other special-care areas.
e
For operating rooms, 100% outside air should be used only when codes require it and only if heat recovery devices are used.
f
“Trauma room” here is a first-aid room and/or emergency room used for general initial treatment of accident victims. The operating room in the trauma
center that is routinely used for emergency surgery should be treated as an operating room.
g
See section on Patient Rooms for discussion of central toilet exhaust system design.
h
“Airborne infectious isolation rooms” here are those that might be used for infectious patients in the average community hospital. The rooms are
negatively pressurized. Some may have a separate anteroom. See the section on Infectious Isolation Unit for more information.
i
Protective-environment rooms are those used for immunosuppressed patients, positively pressurized to protect the patient. Anterooms are generally
required and should be negatively pressurized with respect to the patient room.

36 Phoenix Controls Health Care Facility Design Resource

 Appendix A: Ventilation Requirements for Areas Affecting
Patient Care in Hospitals and Outpatient Facilities (continued)
j
All air need not be exhausted if darkroom equipment has scavenging exhaust duct attached and meets ventilation standards of NIOSH,
OSHA, and local employee exposure limits.
k
A nonrefrigerated body-holding room is only applicable to facilities that do not perform autopsies onsite and use the space for short periods
while waiting for the body to be transferred.
l
Food preparation centers should have an excess of air supply for positive pressurization when hoods are not in operation. The number of air
changes may be reduced or varied for odor control when the space is not in use. Minimum total air changes per hour should be that required
to provide proper makeup air to kitchen exhaust systems. (See Chapter 31, Kitchen Ventilation). Also, exfiltration or infiltration to or from exit
corridors must not compromise exit corridor restrictions of NFPA Standard 90A, pressure requirements of NFPA Standard 96, or the maximum
defined in the table. The number of air changes may be reduced or varied as required for odor control when the space is not in use. See AIA
(2001), Section 7.31.D1.p.
m
Areas with contamination and/or odor problems should be exhausted to the outside and not recirculated to other areas. Individual
circumstances may require special consideration for air exhaust to the outside (e.g., intensive care units where patients with pulmonary
infection are treated, rooms for burn patients). To satisfy exhaust needs, replacement air from the outside is necessary. Minimum outside air
quantities should remain constant while the system is in operation.
n
Relative humidity ranges listed are minimum and maximum limits where control is specifically noted. These limits are not intended to be
independent of space temperature. For example, relative humidity is expected to be at the higher end of the range when the temperature is
also at the higher end, and vice versa.
o
For indicated temperature ranges, systems should be capable of maintaining the rooms at any point within the range during normal
operation. A single figure indicates a heating or cooling capacity to at least meet the indicated temperature. This is usually applicable when
patients may be undressed and require a warmer environment. Use of lower temperature is acceptable when patients’ comfort and medical
conditions require those conditions.
p
NIOSH Criteria Documents 75-137 and 96-107 on waste anesthetic gases and nitrous oxide indicate a need for both local exhaust (scavenging)
systems and general ventilation of area in which these gases are used.
q
Differential pressure between space and corridors should be a minimum of 2.5 Pa. If monitoring device alarms are installed, allowances should
be made to prevent nuisance alarms.
r
Because some surgeons or surgical procedures may require room temperatures outside the indicated range, operating room design
conditions should be developed in consort with all users, surgeons, anesthesiologists, and nursing staff.
s
The first-aid and/or emergency room used for initial treatment of accident victims can be ventilated as for the treatment room. Treatment
rooms used for cryosurgery with nitrous oxide should have provisions for exhausting waste gases.
t
In a recirculating ventilation system, HEPA filters can be used instead of exhausting the air to the outside; return air should pass through the
HEPA filters before being introduced to any other spaces.
u
If exhausting air from an airborne-infection isolation room to the outside is not practical, the air may be returned through HEPA filters to the
air-handling system exclusively serving the isolation room.
v
Total air changes per room for patient rooms, and labor/delivery/recovery/postpartum rooms may be reduced to four when using
supplemental heating and/or cooling systems (radiant heating and cooling, baseboard heating, etc.).
w
Protective-environment airflow design specifications protect the patient from common environmental airborne infectious microbes (e.g.,
Aspergillus spores). They should provide directed airflow from the cleanest patient area to less clean areas. HEPA filters at 99.9% efficiency to 0.3
µm should be used in the supply airstream, to protect patient rooms from environmental microbes in ventilation system components.
Recirculation HEPA filters can be used to increase equivalent room air exchanges. Constant-volume airflow is required for consistent
ventilation. If design criteria indicate that airborne-infection isolation is necessary for protective-environment patients, an anteroom should
be provided. Rooms with reversible airflow provisions (to allow switching between protective-environment and airborne-infection isolation)
are not acceptable (AIA 2001).
x
“Infectious disease isolation (AII) room” here is one used to isolate the airborne spread of infectious diseases, such as measles, varicella, or
tuberculosis. Design should include provision for normal patient care during periods not requiring isolation. Supplemental recirculating
devices may be used in the patient room to increase the equivalent room air exchanges; however, they do not provide outside air require-
ments. Air may be recirculated within individual isolation rooms if HEPA filters are used. Rooms with reversible airflow provisions (to allow
switching between protective-environment and AII) are not acceptable (AIA 2001).
y
When required, provide appropriate hoods and exhaust devices for noxious gases or vapors [AIA (2001), see Section 7.31.D14 and 7.31.D15,
and NFPA Standard 99).
z
Simple visual methods such as smoke trail, ball-in-tube, or flutterstrip can be used to verify airflow direction. These devices require a minimum
differential air pressure to indicate airflow direction. Per AIA (2001) guidelines, recirculating devices with HEPA filters may be used in existing
facilities as interim, supplemental environmental controls to meet requirements for airborne infectious agents control. Design limitations
must be recognized. Either portable or fixed systems should prevent stagnation and short-circuiting or airflow. Supply and exhaust locations
should direct clean air to work areas across the infectious source, and then to the exhaust, so that health care workers are not positioned
between the infectious source and the exhaust. Systems design should also allow easy access for schedule preventative maintenance and
cleaning.

Phoenix Controls Health Care Facility Design Resource 37

 Appendix B: Ventilation Requirements for Areas Affecting
Patient Care in Hospitals and Outpatient Facilities
(Partial Table 7.2 from AIA Guidelines for Design and Construction of Hospital
and Health Care Facilities, pp. 79-81)

Air movement
Area designation relationship to adjacent area2
SURGERY AND CRITICAL CARE
Operating/surgical cystoscopic rooms10, 11 Out
Delivery room10 Out
Recovery room10 –
Critical and intensive care –
Newborn intensive care –
Treatment room13 –
Trauma room13 Out
Anaesthesia gas storage In
Endoscopy In
Bronchoscopy11 In
ER waiting rooms In
Triage In
Radiology waiting rooms In
Procedure room Out
NURSING
Patient room –
Toilet room In
Newborn nursery suite –
Protective environment room11, 17 Out
Airborne infection isolation room11, 18 In
Isolation alcove or anteroom17, 18 In/Out
Labor/delivery/recovery –
Labor/delivery/recovery/postpartum –
Patient corridor –
ANCILLARY
Radiology19
X-ray (surgical/critical care and catheterization) Out
X-ray (diagnostic & treatment) –
Darkroom In
Laboratory
General19 –
Biochemistry19 Out
Cytology In
Glass washing In
Histology In
Microbiology19 In
Nuclear medicine In
Pathology In
Serology Out
Sterilizing In
Autopsy room11 In
Nonrefrigerated body-holding room In
Pharmacy Out
DIAGNOSTIC AND TREATMENT
Examination room –
Medication room Out
Treatment room –
Physical therapy and hydrotherapy In
Soiled workroom or soiled holding In
Clean workroom or clean holding Out

38 Phoenix Controls Health Care Facility Design Resource

 Appendix B: Ventilation Requirements for Areas Affecting
Patient Care in Hospitals and Outpatient Facilities (continued)

Air movement
Area designation relationship to adjacent area2
STERILIZING AND SUPPLY
ETO-sterilizer room In
Sterilizer equipment room In
Central medical and surgical supply
Soiled or decontamination room In
Clean workroom Out
Sterile storage Out
SERVICE
Food preparation center20 –
Warewashing In
Dietary day storage In
Laundry, general –
Soiled linen (sorting and storage) In
Clean linen storage Out
Soiled linen and trash chute room In
Bedpan room In
Bathroom In
Janitor’s closet In

2
Design of the ventilation system shall provide air movement which is generally from clean to less clean areas. If any form of variable
air volume or load shedding system is used for energy conservation, it must not compromise the corridor-to-room pressure balancing
relationships or the minimum air changes required by the table.
10
National Institute for Occupational Safety and Health (NIOSH) Criteria Documents regarding Occupational Exposure to Waste
Anesthetic Gases and Vapors, and Control of Occupational Exposure to Nitrous Oxide indicate a need for both local exhaust
(scavenging) systems and general ventilation of the areas in which the respective gases are utilized.
11
Differential pressure shall be a minimum of 0.01” water gauge (2.5 Pa). If alarms are installed, allowances shall be made to prevent
nuisance alarms of monitoring devices.
13
The term trauma room as used here is the operating room space in the emergency department or other trauma reception area that is
used for emergency surgery. The first aid room and/or “emergency room” used for initial treatment of accident victims may be
ventilated as noted for the “treatment room.” Treatment rooms used for Bronchoscopy shall be treated as Bronchoscopy rooms.
Treatment rooms used for cryosurgery procedures with nitrous oxide shall contain provisions for exhausting waste gases.
17
The protective equipment airflow design specifications protect the patient from common environmental airborne infectious
microbes (i.e., Aspergillus spores). These special ventilation areas shall be designed to provide directed airflow from the cleanest
patient care area to less clean areas. These rooms shall be protected with HEPA filters at 99.97 percent efficiency for a 0.3 µm sized
particle in the supply airstream. These interrupting filters protect patient rooms from maintenance-derived release of environmental
microbes from the ventilation system components. Recirculation HEPA filters can be used to increase the equivalent room air
exchanges. Constant volume airflow is required for consistent ventilation for the protected environment. If the facility determines
that airborne infection isolation is necessary for protective environment patients, an anteroom should be provided. Rooms with
reversible airflow provisions for the purpose of switching between protective environment and airborne infection isolation functions
are not acceptable.
18
The infectious disease isolation room described in these guidelines is to be used for isolating the airborne spread of infectious
diseases, such as measles, varicella, or tuberculosis. The design of airborne infection isolation (AII) rooms should include the provision
for normal patient care during periods not requiring isolation precautions. Supplemental recirculating devices may be used in the
patient room, to increase the equivalent room air exchanges; however, such recirculating devices do not provide the outside air
requirements. Air may be recirculated within individual isolation rooms if HEPA filters are used. Rooms with reversible airflow
provisions for the purpose of switching between protective environment and AII functions are not acceptable.
19
When required, appropriate hoods and exhaust devices for the removal of noxious gases or chemical vapors shall be provided (see
Sections 7.31.D14 and 7.31.D15 and NFPA 99).
20
Food preparation centers shall have ventilation systems whose air supply mechanisms are interfaced approximately with exhaust
hood controls or relief vents so that exfiltration or infiltration to or from exit corridors does not compromise the exit corridor
restrictions of NFPA 90A, the pressure requirements of NFPA 96, or the maximum defined in the table. The number of air changes
may be reduced or varied to any extent required for odor control when the space is not in use. See Section 7.31.D1.p.

Phoenix Controls Health Care Facility Design Resource 39

 Bibliography
Many national building codes are adopted by a state or locality in entirety or with amendments. These
national codes may also reference various isolation room requirements that differ from the CDC, AIA and
ASHRAE guidelines. It is highly recommended that all relevant state or provincial and local building codes
be reviewed with regard to isolation rooms. Reviews and discussions with the health care facilities’
engineering and infectious disease control staff are also essential to incorporate the appropriate design
requirements.

American Institute of Architects (AIA) Academy of Architecture for Health, Facilities

Guidelines Institute (with assistance from the U.S. Department of Health and Human
Services). Guidelines for Design and Construction of Hospital and Health Care Facilities.
Washington, DC: AIA, 2001.
American Industrial Hygiene Association (AIHA). American National Standard for Labo-
ratory Ventilation (ANSI/AIHA Z9.5-2003). Fairfax, VA: AIHA, 2003.
American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE).
2003 ASHRAE Handbook: HVAC Applications. Atlanta, GA: ASHRAE, 2003.
Department of Health and Human Services, Centers for Disease Control and Prevention
(CDC). “CDC Guidelines for Preventing the Transmission of Mycobacterium Tuberculo-
sis in Health-Care Facilities, 1994; Notice.” Federal Register, Vol. 59, No. 208, October 28,
1994.
Department of Health and Human Services, Centers for Disease Control and Prevention
(CDC). “Guidelines for Environmental Infection Control in Health-Care Facilities.” MMWR
Recommendations and Reports, 52(RR10); 1-42, June 6, 2003. Available online at http://
www.cdc.gov/mmwr/preview/ mmwrhtml/rr5210a1.htm.

40 Phoenix Controls Health Care Facility Design Resource

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