ANSI/ASHRAE/ASHE Standard 170-2021
(Supersedes ANSI/ASHRAE/ASHE Standard 170-2017)
Includes ANSI/ASHRAE/ASHE addenda listed in Appendix F
Ventilation of
Health Care Facilities
See Appendix F for approval dates by the ASHRAE Standards Committee, the ASHRAE Board of Directors, the ASHE
Board of Directors, and the American National Standards Institute.
This Standard is under continuous maintenance by a Standing Standard Project Committee (SSPC) for which the Standards
Committee has established a documented program for regular publication of addenda or revisions, including procedures for
timely, documented, consensus action on requests for change to any part of the Standard. Instructions for how to submit a
change can be found on the ASHRAE® website (https://www.ashrae.org/continuous-maintenance).
The latest edition of an ASHRAE Standard may be purchased from the ASHRAE website (www.ashrae.org) or from
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© 2021 ASHRAE
ISSN 1041-2336
ASHRAE Standing Standard Project Committee 170
Cognizant TC: 9.6, Healthcare Facilities
SPLS Liaison: Russell C. Tharp
Michael P. Sheerin, Chair
Frederick E. Granzow, Secretary (2018–2020)
Jonathan J. Flannery, Secretary (2017–2018)
David J. Anderson
George A. Augustini
Amit Bhansali
Robert Booth
Randy Brannen
Brendon J. Burley
Roger V. Brown
Philip T. Cantin
David C. Castillo
Sarah Clock
Abdel K. Darwich
Mark Davidson
John M. Dombrowski
Travis R. English
Douglas S. Erickson
Sama Fakhimi
Jeremy P. Fauber
Steven D. Friedman
Glenn Saint Aubin Gall
Frederich E. Granzow
Danette J. Hauck
Caleb Haynes
Robert N. Heinlein, Jr.
Richard D. Hermans
Nolan Hosking
Aaron L. Johnson
Michael R. Keen
Dan Koenigshofer
Paul R. Kondrat
Peter H. Langowski
Roger W. Lautz
Pavel V. Likhonin
Michael D. Locke
Stephanie J. Mages
David M. Mason
Kenneth R. Mead
Farhad Memarzadeh
James S. Merlino
Michael S. Meteyer
Richard D. Moeller
Kenneth A. Monroe
Paul T. Ninomura
Russell N. Olmsted
Justin M. Opperman
Erick A. Phelps
Heather L. Platt Gulledge
Zaccary A. Poots
Benjamin D. Rosenborough
Chris P. Rousseau
Maya Salabasheva
Amber M. Scales
Kevin A. Scarlett
Charles J. Seyffer
Gordon P. Sharp
Erica Stewart
Ronald L. Westbrook
ASHRAE STANDARDS COMMITTEE 2020–2021
Drury B. Crawley, Chair
Srinivas Katipamula
David Robin
Rick M. Heiden, Vice Chair
Els Baert
Charles S. Barnaby
Robert B. Burkhead
Thomas E. Cappellin
Douglas D. Fick
Walter T. Grondzik
Susanna S. Hanson
Jonathan Humble
Gerald J. Kettler
Essam E. Khalil
Malcolm D. Knight
Jay A. Kohler
Larry Kouma
Cesar L. Lim
James D. Lutz
Karl L. Peterman
Erick A. Phelps
Lawrence J. Schoen
Steven C. Sill
Richard T. Swierczyna
Christian R. Taber
Russell C. Tharp
Theresa A. Weston
Craig P. Wray
Jaap Hogeling, BOD ExO
William F. McQuade, CO
Connor Barbaree, Senior Manager of Standards
SPECIAL NOTE
This American National Standard (ANS) is a national voluntary consensus Standard developed under the auspices of ASHRAE. Consensus is defined by the American
National Standards Institute (ANSI), of which ASHRAE is a member and which has approved this Standard as an ANS, as “substantial agreement reached by directly
and materially affected interest categories. This signifies the concurrence of more than a simple majority, but not necessarily unanimity. Consensus requires that all
views and objections be considered, and that an effort be made toward their resolution.” Compliance with this Standard is voluntary until and unless a legal jurisdiction
makes compliance mandatory through legislation.
ASHRAE obtains consensus through participation of its national and international members, associated societies, and public review.
ASHRAE Standards are prepared by a Project Committee appointed specifically for the purpose of writing the Standard. The Project Committee Chair and
Vice-Chair must be members of ASHRAE; while other committee members may or may not be ASHRAE members, all must be technically qualified in the subject
area of the Standard. Every effort is made to balance the concerned interests on all Project Committees.
The Senior Manager of Standards of ASHRAE should be contacted for
a. interpretation of the contents of this Standard,
b. participation in the next review of the Standard,
c. offering constructive criticism for improving the Standard, or
d. permission to reprint portions of the Standard.
DISCLAIMER
ASHRAE uses its best efforts to promulgate Standards and Guidelines for the benefit of the public in light of available information and accepted industry practices.
However, ASHRAE does not guarantee, certify, or assure the safety or performance of any products, components, or systems tested, installed, or operated in
accordance with ASHRAE’s Standards or Guidelines or that any tests conducted under its Standards or Guidelines will be nonhazardous or free from risk.
ASHRAE INDUSTRIAL ADVERTISING POLICY ON STANDARDS
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industry. The creation of ASHRAE Standards and Guidelines is determined by the need for them, and conformance to them is completely voluntary.
In referring to this Standard or Guideline and in marking of equipment and in advertising, no claim shall be made, either stated or implied, that the product has
been approved by ASHRAE.
CONTENTS
ANSI/ASHRAE/ASHE Standard 170-2021
Ventilation of Health Care Facilities
SECTION
PAGE
Foreword ..................................................................................................................................................................... 2
1 Purpose............................................................................................................................................................. 2
2 Scope ................................................................................................................................................................ 3
3 Definitions ......................................................................................................................................................... 3
4 Compliance ....................................................................................................................................................... 5
5 Planning ............................................................................................................................................................ 6
6 Systems and Equipment ................................................................................................................................... 7
7 Space Ventilation—Inpatient Spaces.............................................................................................................. 13
8 Space Ventilation—Outpatient Spaces ........................................................................................................... 24
9 Space Ventilation—Residential Health, Care, and Support Spaces ............................................................... 32
10 Construction and System Start-Up.................................................................................................................. 36
11 Normative References..................................................................................................................................... 37
Informative Appendix A: Operations and Maintenance (O&M) Procedures .......................................................... 39
Informative Appendix B: Thermal Comfort ............................................................................................................ 41
Informative Appendix C: Air Classifications........................................................................................................... 42
Informative Appendix D: Recommended Filter Efficiencies by Space Type ......................................................... 43
Informative Appendix E: Informative References and Bibliography ...................................................................... 44
Informative Appendix F: Addenda Description Information ................................................................................... 46
NOTE
Approved addenda, errata, or interpretations for this standard can be downloaded free of charge from the ASHRAE
website at www.ashrae.org/technology.
© 2021 ASHRAE
180 Technology Parkway NW · Peachtree Corners, GA 30092 · www.ashrae.org · All rights reserved.
ASHRAE is a registered trademark of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
ANSI is a registered trademark of the American National Standards Institute.
(This foreword is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed
according to the ANSI requirements for a standard and may contain material that has
not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)
FOREWORD
The 2021 edition of ASHRAE/ASHE Standard 170 includes significant improvements to the
2017 edition. Most notably, the 2021 edition incorporates content in support of the new framework introduced in 2017, which divided the standard into three distinct sections: hospital
spaces, outpatient spaces, and nursing home spaces. The added content facilitates closer coordination between the standard and the Facility Guidelines Institute (FGI) documents, which, as
of 2018, comprise three separate books:
• Guidelines for Design and Construction of Hospitals
• Guidelines for Design and Construction of Outpatient Facilities
• Guidelines for Design and Construction of Residential Health, Care, and Support Facilities
As a continuous maintenance document, Standard 170 publishes addenda continually and
updates on a four-year cycle in alignment with the FGI documents.
Improvements to the 2021 edition include the following:
• Revised scope, with improved guidance on thermal comfort conditions provided
• Extensive modifications to address the Outpatient and Residential sections
• Addition of a new outpatient ventilation table to address nonacute-type spaces
• Extensive revisions to air filtration requirements
• Addition of new columns in the ventilation tables to prescribe filtration requirement and
designate unoccupied turndown
• Expanded guidance on separation distance requirements for varied intake and exhaust
arrangements, coordinating with related ASHRAE Standard 62.1 data
• Expanded requirements to allow airborne infectious isolation room exhaust discharge to
general exhaust under certain conditions
• Improved guidance on space ventilation requirements needed for anesthetic gas use
• Clarification of Class 1/Class 2/Class 3 imaging in coordination with FGI
• Revised definition of “invasive procedure”
• Improved guidance related to behavioral and mental health
The committee appreciates the hard work invested in this edition by everyone who participated. We are grateful for the partnership with FGI and other ASHRAE committees. The committee also appreciates the feedback received from the public review and continuous
maintenance proposal processes. Future input from the public is always welcome.
This standard does not constitute a design guide. Rather it comprises a set of minimum
requirements intended for adoption by code-enforcing agencies. For wide-ranging guidance,
we refer the user to ASHRAE Handbook—HVAC Applications, HVAC Design Manual for
Hospitals and Clinics and the proposed ASHRAE Guideline 43, Operations Guideline for Ventilation of Health Care Facilities.
Standard 170 originated with an agreement between ASHRAE and the Facility Guidelines
Institute (publishers of the Guidelines for Design and Construction of Health Care Facilities)
that an ASHRAE standard would provide the best location for ventilation requirements for the
health care industry. The American Society for Health Care Engineering (ASHE) was also
included in this process, which resulted in the initial (2008) edition of this standard—the first
standard jointly sponsored by ASHRAE and ASHE.
1. PURPOSE
The purpose of this standard is to define ventilation system design requirements that provide
environmental control in health care facilities.
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ANSI/ASHRAE/ASHE Standard 170-2021
2. SCOPE
2.1 The requirements in this standard apply to patient care areas, resident care areas, and
related support areas within health care facilities.
2.2 This standard applies to new buildings, additions to existing buildings, and those alterations to existing buildings that are identified within this standard.
2.3 This standard considers chemical, physical, and biological contaminants that can affect the
delivery of medical care to patients and residents; the convalescence of patients and residents;
and the safety of patients, residents, health care workers, and visitors.
2.4 This standard establishes design requirements for temperature and humidity.
2.5 This standard establishes design requirements for odor control and asepsis.
2.6 This standard establishes design requirements for ventilation rates, including, but not limited to, outdoor air to serve health care facilities.
2.7 This standard does not establish comprehensive thermal comfort design requirements.
3. DEFINITIONS
absorption distance: the distance downstream of a humidifier required for all moisture to be
absorbed into the airstream.
addition: an extension or increase in floor area or height of a building, building system, or
equipment.
airborne infection isolation (AII): the isolation of patients infected with organisms spread by
airborne droplet nuclei less than 5 µm in diameter. For the purposes of this standard, the abbreviation “AII” refers to the room that provides isolation. (Informative Note: See FGI [2018a,
2018b, 2018c], CDC [2003], and CDC [2005] in Informative Appendix E.)
airborne infection isolation (AII) room: a room that is designed according to the requirements
of this standard and that is intended to provide airborne infection isolation.
alteration: a significant change in the function or size of a space, in the use of its systems, or in
the use of its equipment, either through rearrangement, replacement, or addition. Routine
maintenance and service shall not constitute an alteration.
authority having jurisdiction (AHJ): the agent or agency responsible for enforcing this standard.
average velocity: the volumetric flow rate obtained by dividing the air quantity issuing from an
air distribution device by the nominal face area of the device.
building: a structure that is wholly or partially enclosed within exterior walls and a roof, or
within exterior and party walls and a roof, and that affords shelter to persons, animals, or
property. In this standard, a building is a structure intended for use as a hospital or health care
facility.
Class 1 imaging room: diagnostic radiography, fluoroscopy, mammography, computed tomography (CT), ultrasound, magnetic resonance imaging (MRI), nuclear medicine, and other
imaging modalities, including services that use natural orifice entry and do not pierce or penetrate natural protective membranes.
Class 2 imaging room: diagnostic and therapeutic procedures such as coronary, neurological,
or peripheral angiography, including electrophysiology, cardiac catheterization, and interventional angiography and similar procedures.
Class 3 imaging room: invasive procedures including cardiac stenting, implantation of devices
in an invasive fluoroscopy, and any other Class 2 procedure during which the patient will
require physiological monitoring and is anticipated to require active life support.
equipment: devices for heating, ventilating, and/or air conditioning, including but not limited
to furnaces, boilers, air conditioners, heat pumps, chillers, and heat exchangers.
essential accessories: those components of a system, required to allow proper operation of that
system, that are reasonably subject to mechanical failure (e.g., pumps, fans, control air compressors). Humidifiers, controls, and tanks are not included in this definition.
ANSI/ASHRAE/ASHE Standard 170-2021
3
facility: a discrete physical entity composed of various functional units as described in the FGI
Guidelines. (Informative Note: This may be a portion of a building or a portion of a floor
within a building.)
health care facility: an inpatient, outpatient, or residential health, care, and support facility.
high-risk immunocompromised patients: patients who have the greatest risk of infection
caused by airborne or waterborne microorganisms. These patients include but are not limited to
allogeneic stem-cell transplant patients and intensive chemotherapy patients.
immunocompromised patients: patients whose immune mechanisms are deficient because of
immunologic disorders, chronic diseases, or immunosuppressive therapy.
Informative Notes:
1. Examples of immunologic disorders include human immunodeficiency virus (HIV)
infection or congenital immune deficiency syndrome.
2. Examples of chronic diseases include diabetes, cancer, emphysema, or cardiac failure.
3. Examples of immunosuppressive therapy include radiation, cytotoxic chemotherapy, antirejection medication, or steroids.
4. For more information, see CDC (2003) in Informative Appendix E.
infection control risk assessment (ICRA): a determination of the potential risk of transmission
of various infectious agents in the facility, a classification of those risks, and a list of required
practices for mitigating those risks during construction or renovation.
inpatient: a patient whose stay at the health care facility is anticipated to require twenty-four
hours or more of patient care.
invasive fluoroscopy: therapeutic or diagnostic invasive procedures that require fluoroscopic
imaging (e.g., cardiac catheterization, interventional angiography, cardiac stenting, or implantation of devices). (Informative Note: These procedures are typically performed in a restricted
or semirestricted area based on the classification of the imaging procedure being performed.
Refer also to Class 2 imaging room for cardiac catheterization or interventional angiography
and Class 3 imaging room for cardiac stenting or implantation of devices.)
invasive procedure: a procedure that is performed in an aseptic surgical field and penetrates
the protective surfaces of a patient’s body (e.g., subcutaneous tissue, mucous membranes, cornea). An invasive procedure may fall into one or more of the following categories:
a. Requires entry into, or opening of, a sterile body cavity (i.e., cranium, chest, abdomen,
pelvis, joint spaces)
b. Involves insertion of an indwelling foreign body
c. Includes excision and grafting of burns that cover more than 20% of total body area
d. Does not begin as an open procedure but has a recognized measurable risk of requiring
conversion to an open procedure
(Informative Notes:
1. Invasive procedures are performed in locations suitable to the technical requirements of the procedure with consideration of infection control and anesthetic risks
and goals. Accepted standards of patient care are used to determine where an invasive procedure is performed. “Invasive procedure” is a broad term commonly used
to describe procedures ranging from a simple injection to a major surgical procedure. For the purposes of this document, the term is limited to the above description. The intent is to differentiate those procedures that carry a high risk of
infection, either by exposure of a usually sterile body cavity to the external environment or by implantation of a foreign object into a normally sterile site. Procedures performed through orifices normally colonized with bacteria, and
percutaneous procedures that do not involve an incision deeper than skin, would
not be included in this definition.)
2. Definition is adapted from the FGI Guidelines; see FGI [2018a, 2018b] in Informative Appendix E.)
nonaspirating diffuser: a diffuser that has unidirectional downward airflow from the ceiling
with minimum entrainment of room air. Classified as ASHRAE Group E, these diffusers generally have very low average velocity. For the purposes of this standard, the performance of
these diffusers is to be measured in terms of average velocity.
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ANSI/ASHRAE/ASHE Standard 170-2021
nursing facility: a facility that provides resident care, treatment, and services areas (including
skilled nursing, subacute care, and Alzheimer’s and other dementia facilities).
operating room (OR): a room in the surgical suite that meets the requirements of a restricted
area and is designated and equipped for performing invasive procedures. (Informative Note:
Definition is adapted from the FGI Guidelines; see FGI [2018a, 2018b] in Informative
Appendix E.)
outpatient: a patient whose stay at the health care facility does not meet the standard’s definition of “inpatient.”
patient: a person receiving medical, surgical, or psychiatric care.
patient care area: an area used primarily for the provision of clinical care to patients. Such
care includes monitoring, evaluation, and treatment services.
procedure room: a room designated for the performance of patient care that requires high-level
disinfection or sterile instruments and some environmental controls but is not required to be
performed with the environmental controls of an operating room. (Informative Note: Definition is adapted from the FGI Guidelines; see FGI [2018a, 2018b] in Informative Appendix E.)
protective environment (PE) room: a patient room that is designed according to this standard
and intended to protect a high-risk immunocompromised patient from human and environmental airborne pathogens.
resident: a person living and receiving health, care, and/or support services in a nursing home,
hospice facility, assisted living facility, independent living setting, or inpatient rehabilitation
facility.
resident care area: an area used primarily for the provision of health and/or care services to
residents. (Informative Note: Resident care and service include, but are not limited to, activities, personal care, food service, and medication administration.)
residential care and support facilities: category of facilities in which services such as assistance with activities of daily living (ADL) and/or instrumental activities of daily living (IADL)
are provided to residents. For the purposes of this standard, these are assisted-living facilities.
residential health facilities: category of facilities in which long-term health services are provided. For the purposes of this standard, these are nursing homes and hospice facilities.
restricted area: a designated space in the semirestricted area of the surgical suite that can only
be accessed through a semirestricted area. The restricted access is primarily intended to support a high level of asepsis control, not necessarily for security purposes. Traffic in the
restricted area is limited to authorized personnel and patients. Personnel in restricted areas are
required to wear surgical attire and cover head and facial hair. Masks are required where open
sterile supplies or scrubbed persons may be located. (Informative Note: Definition is adapted
from the FGI Guidelines; see FGI [2018a, 2018b] in Informative Appendix E.)
triage: the process of determining the severity of the illness of or injury to patients so that
those who have the most emergent illnesses/injuries can be treated immediately and those less
severely injured can be treated later or in another area.
4. COMPLIANCE
4.1 Compliance Requirements
4.1.1 New Buildings. New buildings shall comply with the provisions of this standard.
4.1.2 Existing Buildings
4.1.2.1 Additions to Existing Buildings. Additions shall comply with the provisions of
this standard.
4.1.2.2 Alterations to Existing Buildings. Portions of a heating, ventilating, and airconditioning system and other systems and equipment that are being altered shall comply
with the applicable requirements of this standard.
4.1.2.2.1 Heating, Ventilation, and Air-Conditioning System Alterations. Alterations
to mechanical systems serving the building heating, cooling, or ventilating needs shall comply
with the requirements of Section 6, “Systems and Equipment,” applicable to those specific portions of the building and its systems that are being altered. Any new mechanical equipment
ANSI/ASHRAE/ASHE Standard 170-2021
5
installed in conjunction with the alteration as a direct replacement of existing mechanical
equipment shall comply with the provisions of Sections 6.2, 6.4, 6.5, and 6.6.
4.1.2.2.2 Space Alterations. Alterations to spaces listed in Tables 7-1, 8-1, 8-2, and 9-1
shall comply with the requirements of Sections 6.7, 7, 8, and 9, applicable to those specific
portions of the building and its systems that are being altered. Any alteration to existing patient
or resident care space in a building that will continue to treat patients during construction shall
comply with Sections 5.4, 5.5, 10.1, 10.2.5.
4.2 Administrative Requirements. Administrative requirements relating to permit requirements, enforcement by the authority having jurisdiction (AHJ), interpretations, claims of
exemption, approved calculation methods, rights of approved calculation methods, and rights
of appeal are specified by the AHJ.
4.3 Compliance Documents
4.3.1 General. Compliance documents are those plans, specifications, engineering calculations, diagrams, reports, and other data that are approved as part of the permit by the AHJ. The
compliance documents shall include all specific construction-related requirements of the
owner’s infection control risk assessment.
4.3.2 Construction Details. Compliance documents shall contain all pertinent data and features of the building, equipment, and systems in sufficient detail to allow a determination of
compliance by the AHJ and to indicate compliance with the requirements of this standard.
4.3.3 Supplemental Information. Supplemental information necessary to verify compliance with this standard, such as calculations, worksheets, compliance forms, vendor literature,
or other data, shall be made available when required by the AHJ.
4.4 Alternate Materials, Methods of Construction, or Design. The provisions of this standard are not intended to prevent the use of any material, method of construction, design, or
building system not specifically prescribed herein, provided that such construction, design, or
building system has been approved by the AHJ as meeting the intent of this standard.
4.5 Informative Appendices. The informative appendices to this standard and informative
notes located within this standard contain recommendations, explanations, and other nonmandatory information and are not part of this standard.
4.6 Criteria Ranges. This standard often specifies a range of values that will comply with a
specific requirement of the standard. If it is permitted by the AHJ, compliance with this
requirement may be achieved by the presentation of compliance documents that demonstrate a
system’s ability to perform within the specified range.
4.7 Space Planning. In a building that contains spaces programmed for inpatient use as well
as spaces programmed for outpatient use, the inpatient care spaces shall be designed solely for
inpatient use and the outpatient care spaces shall be designed solely for outpatient use. Individual spaces that are dual programmed for either inpatient use or outpatient use shall meet the
design requirements for inpatient use of the space.
5. PLANNING
5.1 General. Space programming and planning details that impact the HVAC design shall be
identified and addressed in the planning phase of design.
a. Facilities without operating rooms, that consist of spaces designed solely for outpatient or
residential health, care, and support use, need only comply with Sections 5.2, 5.3, and 5.4.
5.2 Owner Requirements. Owners/managers of health care facilities shall do the following:
a. Space Program. Prepare a space program, including the clinical service expected in each
space and specific user equipment to be used. The program shall include space names and
paragraph numbering references from the applicable version of the relevant FGI Guidelines
for each space noted within the program (Informative Note: see FGI [2018a, 2018b, and
2018c] in Informative Appendix E). Specify needs for temperature, humidity, air filtration,
localized and general exhaust, and pressure control that are not covered or are different than
the requirements in this standard.
b. Medical/Clinical Organizations. Provide specific medical and clinical requirements that
are different than the requirements in this standard.
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ANSI/ASHRAE/ASHE Standard 170-2021
c. Facility Operational Plan. Provide an operational plan in event of extended power or fuel
outage. See Sections 6.1.2.1 and 6.1.2.2.
5.3 Planning for HVAC Services in a New Facility. Design documents for new construction
shall meet the following requirements:
a. Mechanical Equipment
1. Locate mechanical rooms to avoid the intrusion of maintenance personnel into surgical,
critical-care-patient, or other patient- or medical-staff-sensitive areas.
2. Provide sufficient space to comply with HVAC equipment manufacturers’ minimum
required access for operation, maintenance, and replacement.
3. Provide safe and practical means of accessing equipment.
4. Floors in mechanical rooms shall be sealed—including sealing around all penetrations—when they are above surgical suites and critical care spaces.
b. Space Allocation for HVAC Distribution Systems
1. HVAC Distribution Systems. Coordinate ceiling plenum height, underfloor, and other
areas where HVAC distribution systems are intended to be installed to allow for installation, inspection, and maintenance.
2. Mechanical Shafts. Allow for needed access for damper installation (if required),
inspection, and service. Access doors shall be sized to meet code minimum for service
requirements.
5.4 Planning for the HVAC Services in an Existing Facility. If any existing air-handling,
cooling, or heating equipment is to be reused, the designer shall evaluate the capacity of the
equipment to determine whether it will meet the requirements of this standard for the remodeled space.
5.5 Planning for Infection Control During Remodeling of an Existing Facility. Where
required, prior to beginning modifications or remodeling of HVAC systems in an existing facility, an owner shall conduct an infection control risk assessment (ICRA). The ICRA shall establish those procedures required to minimize the disruption of facility operation and the
distribution of dust, odors, and particulates.
5.6 Planning for HVAC Systems Operating During Construction. Owner and design team
shall determine if, and under what conditions, the permanent HVAC systems can be used for
providing temporary heating, cooling, and/or dehumidifying during construction. Refer to Section 10.1.4.3(b).
6. SYSTEMS AND EQUIPMENT
Air-handling and distribution systems are required to provide health care facilities not only
with a comfortable environment but also with ventilation to dilute and remove contaminants,
provide conditioned air, and assist in controlling the transmission of airborne infection. In
order to meet these requirements, air-handling and distribution systems shall be designed
according to the requirements of this standard.
6.1 Utilities
6.1.1 Ventilation Upon Loss of Electrical Power. The space ventilation and pressure relationship requirements of Tables 7-1, 8-1, and 9-1 shall be maintained for the following spaces,
even in the event of loss of normal electrical power:
a. AII rooms
b. Protective environment (PE) rooms (inpatient only)
c. Operating rooms (ORs), including delivery rooms (Caesarean) (inpatient and outpatient only)
Exception to 6.1.1: When an essential power system is not provided or required, operation
of space ventilation and pressure relationships is not required.
Informative Note: For further information, see NFPA 99 (2021) in Informative Appendix E.
6.1.2 Heating and Cooling Sources
6.1.2.1 Provide heat sources and essential accessories in number and arrangement sufficient to accommodate the facility needs (reserve capacity), even when any one of the heat
sources or essential accessories is not operating due to a breakdown or routine maintenance.
The capacity of the remaining source or sources shall be sufficient to provide for domestic hot
ANSI/ASHRAE/ASHE Standard 170-2021
7
water, sterilization, and dietary purposes and to provide heating for operating, delivery, birthing, labor, recovery, emergency, intensive care, nursery, and resident care areas and inpatient/
resident rooms. Fuel sufficient to support the owner’s facility operation plan upon loss of fuel
service shall be provided on site.
Exception to 6.1.2.1: Reserve capacity is not required if the ASHRAE 99% heating drybulb temperature for the facility is greater than or equal to 25°F (–4°C).
6.1.2.2 Inpatient and Residential Health Care Spaces. For central cooling systems
greater than 400 tons (1407 kW) peak cooling load, the number and arrangement of cooling
sources and essential accessories shall be sufficient to support the owner’s facility operation
plan upon a breakdown or routine maintenance of any one of the cooling sources.
6.2 Air-Handling Unit (AHU) Design
6.2.1 AHU Casing. The casing of the AHU shall be designed to prevent water intrusion,
resist corrosion, and permit access for inspection and maintenance. All airstream surfaces of
AHUs shall comply with ASHRAE Standard 62.1 1, Section 5.4.
6.3 Outdoor Air Intakes and Exhaust Discharges
6.3.1 Outdoor Air Intakes
6.3.1.1 General. Outdoor air intakes for AHUs shall be located such that the shortest distance from the intake to any specific potential outdoor contaminant source shall be equal to or
greater than the separation distance listed in Table 6-1 and comply with all other requirements of
this section. New facilities with moderate-to-high risk of natural or man-made extraordinary
incidents shall locate air intakes away from public access. All intakes shall be designed to prevent the entrainment of wind-driven rain, shall contain features for draining away precipitation,
and shall be equipped with a birdscreen of mesh no smaller than 0.5 in. (13 mm).
Exception to 6.3.1.1:
1. For gas-fired, packaged rooftop units, the separation distance of the unit’s outdoor
air intake from its flue may be less than 25 ft (8 m). The separation distance shall be
greater than or equal to the distance prescribed in ASHRAE Standard 62.1 1, Table
5-1, “Air Intake Minimum Separation Distance.”
2. For plumbing vents terminating with stack-type air admittance valves installed less
than 3 ft (1m) above the level of the outdoor air intake, the minimum separation distance may be 10 ft (3 m). For plumbing vents terminating with stack-type air admittance valves installed at least 3 ft (1m) above the level of the outdoor air intake, the
minimum separation distance may be 3 ft (1 m).
3. If permitted by the AHJ, based on an engineering analysis of reentrainment, separation distances may be decreased below Table 6-1 values for cooling towers and
exhaust and vent discharges, and an alternate location may be used. The submitted
reentrainment analysis shall demonstrate that an exhaust discharge outlet located at
a distance less than required by Table 6-1 provides a lower concentration of reentrainment than all the areas located at a distance greater than required by Table 6-1
on the roof level where the exhaust discharge is located. (Informative Note: For
example, located adjacent to an air intake but with the exhaust discharge point
above the top of the air intake.)
6.3.1.2 Air-Handling System Controls. Provide air-handling systems and equipment with
manual or automatic controls to maintain the required space minimum outdoor airflow and
space minimum total air changes per hour under all design conditions, including any space
unoccupied turndown conditions.
6.3.1.2.1 All systems shall allow for field verification of outdoor air intake flow during
operation and be provided with manual or automatic controls to maintain not less than the outdoor air intake flow required by Section 7, Section 8, and Section 9 under all load conditions or
unoccupied turndown conditions.
6.3.1.3 Relief Air. Air that could be returned to the AHU from the occupied spaces but is
being discharged to the outdoors to maintain building pressurization (such as during air-side
economizer operation) is exempt from the separation requirement listed in Table 6-1 for the
respective AHU’s outdoor air intake opening.
Informative Note: For more information, see Informative Appendix C and ASHRAE
Standard 62.1 (ASHRAE 2019a) in Informative Appendix E.
8
ANSI/ASHRAE/ASHE Standard 170-2021
Table 6-1 Air Intake Minimum Separation Distance
Potential Outdoor Contaminant Source
Minimum Distance, ft (m)
Class 2 air outlet
10 (3)
Required exhaust from ASHRAE Standard 62.1, Table 6-2, or other codes
25 (7.5)
Required exhaust from Table 7-1, 8-1, 8-2, or 9-1 or Class 3 air exhaust outlet
25 (7.5)
Required exhaust from Section 6.3.2.2 or Class 4 air exhaust outlet
30 (10)
Plumbing vents
25 (7.5)
Vents, chimneys, and flues from combustion appliances and equipment
25(7.5)
Garage entry, automobile loading area, or drive-in queue
See Note 1
Truck loading area or dock, bus parking/idling area
See Note 1
Driveway, landscaped grade, sidewalk, street, or parking place directly below intake
5 (1.6)
Thoroughfare with high vehicle traffic volume
See Note 1
Roof or other above-grade surface directly below intake
3 (1)
Garbage storage/pick-up area, dumpsters
See Note 1
Cooling tower exhaust, intake, or basin
25 (7.5)
1
Note 1: Refer to ASHRAE Standard 62.1 , Table 5-1.
6.3.1.4 Areaways. In the case of an areaway, the bottom of the air intake opening shall be
at least 6 ft (2 m) above grade. The bottom of the air intake opening from the areaway into the
building shall be at least 3 ft (1 m) above the bottom of the areaway.
Informative Note: See Appendix A, Figure A-1.
Exception to 6.3.1.4: Equipment serving nonsurgical spaces designed solely for outpatient or residential health, care, and support use shall not be required to comply with
Sections 6.3.1.1, 6.3.1.2, 6.3.1.3, or 6.3.1.4, provided the equipment complies with
ASHRAE Standard 62.1 1, Table 5-1.
6.3.2 Exhaust Discharges
6.3.2.1 General. Exhaust discharge outlets that discharge air from AII rooms, bronchoscopy and sputum collection and pentamidine administration rooms, emergency department
public waiting areas, nuclear medicine hot labs, radiology waiting rooms programmed to
hold patients who are waiting for chest x-rays for diagnosis of respiratory disease, pharmacy
hazardous-drug exhausted enclosures, and laboratory work area chemical fume hoods shall
a. be designed so that all ductwork within the building is under negative pressure.
Exception to 6.3.2.1(a): Ductwork located within mechanical equipment rooms. Positivepressure exhaust ductwork located within mechanical equipment rooms shall be sealed
in accordance with SMACNA duct leakage Seal Class A 2.
b. be located such that they reduce the potential for the recirculation of exhausted air back
into the building.
6.3.2.2 Additional Requirements
a. Exhaust discharge outlets from AII rooms, bronchoscopy and sputum collection exhaust,
pharmacy hazardous-drug exhausted enclosures, and laboratory work area chemical fume
hoods shall additionally be arranged to discharge to the atmosphere in a vertical direction
(with no rain cap or other device to impede the vertical momentum) and at least 10 ft (3 m)
above the adjoining roof level.
Exception to 6.3.2.2(a): AII room exhaust that first passes through a high-efficiency particulate air (HEPA) filter.
b. Exhaust discharge outlets from laboratory work area chemical fume hoods shall discharge
with a stack velocity of at least 3000 fpm (15.24 L/s).
Exception to 6.3.2.2(b): Lower discharge velocity may be permitted when an engineering
analysis can demonstrate that the specific design meets the dilution criteria necessary
ANSI/ASHRAE/ASHE Standard 170-2021
9
to reduce concentration of hazardous materials in the exhaust to safe levels at all
potential receptors. (See ANSI/AIAH Z9.5 3, Section 2.1.)
c. Exhaust discharge outlets from AII rooms, bronchoscopy and sputum collection exhaust,
and laboratory work area chemical fume hoods shall be located not less than 25 ft (8 m)
horizontally from outdoor air intakes, openable windows/doors, and areas that are normally
accessible to the public.
Exception to 6.3.2.2(c): If permitted by the AHJ, an alternate location may be used
(Informative Note: e.g., located adjacent to an air intake but with the exhaust discharge point above the top of the air intake). The submitted reentrainment analysis
shall demonstrate that an exhaust discharge outlet located at a distance less than 25 ft
(8 m) horizontally provides a lower concentration of reentrainment than all the areas
located at a distance greater than 25 ft (8 m) horizontally on the roof level where the
exhaust discharge is located.
6.3.2.3 Health Care Facilities with Attached Parking Garages. In order to minimize the
entry of vehicular exhaust into occupiable spaces, health care facilities with attached parking
garages shall comply with ASHRAE Standard 62.1 1, Section 5.17.
6.3.3 Combustion Air. Fuel-burning appliances, both vented and unvented, shall comply
with ASHRAE Standard 62.1 1, Section 5.8.
6.4 Filtration. Filtration of mechanically supplied air shall be provided as follows:
a. Particulate matter filters, minimum MERV-8, shall be provided upstream of the first heat
exchanger surface of any air-conditioning system that combines return air from multiple
rooms or introduces outdoor air.
b. Outdoor air shall be filtered in accordance with Table 7-1, 8-1, 8-2, or 9-1.
c. Air supplied from equipment serving multiple or different spaces shall be filtered in accordance with Table 7-1, 8-1, 8-2, or 9-1.
d. Air recirculated within a room shall be filtered in accordance with Table 7-1, 8-1, 8-2, or 9-1,
or Section 7.1(a)(5), 8.1(a)(5), 8.2(a)(5), or 9.1(a)(5).
e. The design shall include all necessary provisions to prevent moisture accumulating on filters located downstream of cooling coils and humidifiers.
f. Minimum filter requirements shall meet the equivalent MERV rating when tested in accordance with ASHRAE Standard 52.2 4.
g. Any HEPA filter or filter MERV-14 or higher shall have sealing interface surfaces. (Informative Note: HEPA filters are those filters that remove at least 99.97% of 0.3 micron sized
particles at the rated flow in accordance with the testing methods of IEST RP CC001.3
[2005] in Informative Appendix E).
h. For spaces that do not permit air recirculated by means of room units and have a minimum
filter efficiency of MERV-14, MERV-16, or HEPA in accordance with Table 7-1, 8-1, or 8-2,
the minimum filter requirement listed in Table 7-1, 8-1, or 8-2 shall be installed downstream
of all wet-air cooling coils and the supply fan.
Informative Note: For more information, see CDC (2003) in Informative Appendix E.
6.4.1 Filter-Bank Blank-Off Panels. Filter-bank blank-off panels shall be permanently
attached to the filter-bank frame, constructed of rigid materials, and have sealing surfaces
equal to or greater than the filter media installed within the filter-bank frame.
6.4.2 Filter Frames. Filter frames shall be durable and proportioned to provide an airtight
fit with the enclosing ductwork. All joints between filter segments and enclosing ductwork
shall have gaskets or seals to provide a positive seal against air leakage.
6.5 Heating and Cooling Systems
6.5.1 Cooling Coils and Drain Pans. Cooling coils and drain pans shall comply with the
requirements of ASHRAE Standard 62.1 1.
6.5.2 Radiant Cooling Systems. If radiant cooling panels are used, the chilled-water temperature shall always remain above the dew-point temperature of the space.
6.5.3 Radiant Heating Systems. If radiant heating is provided for an AII room, a protective
environment room, a wound intensive care unit (burn unit), an OR, or a procedure room, either
flat and smooth radiant ceiling or wall panels with exposed cleanable surfaces or radiant floor
10
ANSI/ASHRAE/ASHE Standard 170-2021
heating shall be used. Gravity-type heating or cooling units, such as radiators or convectors,
shall not be used in ORs and other special care areas.
6.5.4 Cooling Towers. Cooling towers shall be located so that drift is directed away from
AHU intakes. They shall meet the requirements of Section 6.3.2.
6.6 Humidifiers. When outdoor humidity and internal moisture sources are not sufficient to
meet the requirements of Tables 7-1, 8-1, or 9-1, humidification shall be provided by means of
the facility air-handling systems. Steam or adiabatic high-pressure water-atomizing humidifiers shall be used.
6.6.1 General Requirements
a. Locate humidifiers within AHUs or ductwork to avoid moisture accumulation in downstream components, including filters and insulation.
b. A humidity sensor shall be provided, located at a suitable distance downstream from the
injection source.
c. Controls shall be provided to limit duct humidity to a maximum value of 90% rh when the
humidifier is operating.
d. Duct takeoffs shall not be located within the humidifier’s absorption distance.
e. Humidifier control valves shall be designed so that they remain off whenever the AHU is
not in operation.
f. Water for adiabatic high-pressure humidifiers shall comply with Section 6.6.3.
6.6.2 Steam Humidifier Requirements. Chemical additives used in the steam systems that
serve humidifiers shall comply with FDA requirements 5.
6.6.3 Adiabatic Atomizing Humidifier Requirements
a. Humidifier water shall be treated with a reverse osmosis process, a UV-C sterilization light
source, and a submicron filter. (Informative Note: For more information, see ASTM
[2011] in Informative Appendix E.)
b. Treated humidifier water shall be continuously circulated from the source to the humidifier
valves. All valves, headers, and piping not part of the recirculation loop shall drain completely when not in use. Water temperature shall be maintained within the control limits in
the legionellosis risk management plan. (Informative Note: For more information, reference ASHRAE Guideline 12 [2020] and ASHRAE Standard 188 [2018] in Informative
Appendix E.)
c. Ports suitable for testing water quality shall be provided in the treated humidifier water piping system.
d. Moisture eliminators shall be provided as required to prevent moisture accumulation in
ductwork.
e. Water purity shall meet or exceed potable water standards at the point where the water
enters the ventilation system, space, or water-vapor generator.
6.7 Air Distribution Systems
6.7.1 General. Maintain the pressure relationships required in Tables 7-1, 8-1, 8-2, and 9-1
in all modes of HVAC system operation, except as noted in the tables. Spaces that have
required pressure relationships shall be served by fully ducted return systems or fully ducted
exhaust systems. The following additional surgery and critical-care patient care areas that do
not require a pressure relationship to adjacent areas shall also be served by fully ducted return
or exhaust systems: recovery rooms, critical and intensive care areas, intermediate care areas,
and wound intensive care units (burn units). In inpatient facilities, patient care areas shall use
ducted systems for return and exhaust air. Where space pressure relationships are required, the
air distribution system design shall maintain them, taking into account recommended maximum filter loading, heating-season lower airflow operation, and cooling-season higher airflow
operation. Airstream surfaces of the air distribution system shall comply with ASHRAE Standard 62.1 1, Section 5.4. The air distribution system shall be provided with access doors, panels, or other means to allow convenient access for inspection and cleaning.
6.7.2 Air Distribution Devices. All air distribution devices shall meet the following requirements:
a. Surfaces of air distribution devices shall be suitable for cleaning. Supply air outlets in
accordance with Table 6-2 shall be used.
ANSI/ASHRAE/ASHE Standard 170-2021
11
Table 6-2 Supply Air Outlets
Space Designation (According to Function)
Supply Air Outlet Classification a
Operating rooms b, procedure rooms
Supply diffusers within the primary supply diffuser array: Group E, nonaspirating;
Additional supply diffusers within the room: Group E
Protective environment rooms
Group E, nonaspirating
Wound intensive care units (burn units)
Group E, nonaspirating
Trauma rooms (crisis or shock)
Group E, nonaspirating
AII rooms
Group A or Group E
Single-bed patient or resident rooms c
Group A, Group D, or Group E
All other patient care or resident care spaces
Group A or Group E
All other spaces
No requirement
a. Informative Note: Refer to 2017 ASHRAE Handbook—Fundamentals, Chapter 20 (ASHRAE [2017b]), for definitions related to outlet classification and performance.
b. Surgeons may require alternate air distribution systems for some specialized surgeries. Such systems shall be considered acceptable if they meet or exceed the requirements of
this standard.
c. Air distribution systems using Group D diffusers shall meet the following requirements:
1. The system shall be designed according to “Design Guidelines” in System Performance Evaluation and Design Guidelines for Displacement Ventilation 6, Chapter 7.
2. The supply diffuser shall be located where it cannot be permanently blocked (Informative Note: e.g., opposite the foot of the bed).
3. The room return/exhaust grille shall be located in the ceiling, approximately above the head of the patient or resident bed.
4. The transfer grille to the toilet room shall be located above the occupied zone.
b. The supply diffusers in ORs shall be designed and installed to allow for internal cleaning.
c. Psychiatric, seclusion, and holding patient rooms shall be designed with security diffusers,
grilles, and registers.
6.7.3 Smoke Barriers. Where smoke barriers are required, heating, ventilating, and airconditioning zones shall be coordinated with compartmentation to minimize ductwork penetrations of fire and smoke barriers.
6.7.4 Smoke and Fire Dampers
a. Maintenance access shall be provided at all dampers.
b. All damper locations shall be shown on design drawings.
c. Air-handling systems shall be arranged such that damper activation will not damage ducts.
6.7.5 Duct Penetrations. Ducts that penetrate construction intended to protect against x-ray,
magnetic, radio frequency interference (RFI), or other radiation shall not impair the effectiveness of the protection, nor shall the treatment of these penetrations impair the ventilation of the
space served.
6.7.6 Air Balancing
6.7.6.1 Designing for Air Balancing. The air distribution system shall be provided with
means to adjust the system to achieve at least the minimum outdoor airflow and the minimum
total air changes per hour as required by Section 7, Section 8, and Section 9 under any load
condition.
6.7.6.2 Plenum Systems. When the ceiling or floor plenum is used to recirculate return to
ceiling- or floor-mounted terminal units, the plenum system shall not be used to distribute outdoor air.
Informative Note: Systems with direct connection of outdoor air ducts to terminals units,
for example, comply with this requirement.
6.7.6.3 Documentation. The design documents shall specify minimum requirements for
air balance testing or reference applicable national standards for measuring and balancing airflow.
6.7.7 Building Exfiltration. Outdoor air ventilation systems for a building shall be designed
such that the total building outdoor air intake equals or exceeds the total building exhaust under
all load and unoccupied turndown conditions.
Exception to 6.7.7: Where an imbalance is required by process considerations and approved
by the AHJ.
12
ANSI/ASHRAE/ASHE Standard 170-2021
6.8 Energy Recovery Systems
6.8.1 General. Energy recovery systems shall be located upstream of filters required by Section 6.4. If energy recovery systems are used, the systems shall not allow for any amount of
cross-contamination of exhaust air back to the supply airstream via purge, leakage, carryover,
or transfer except as allowed in Section 6.8.3.
Exception to 6.8.1: Energy recovery systems that comply with the leakage and carryover
limitations of ASHRAE Standard 62.1 1 shall be permitted in residential health, care,
and support facilities.
6.8.2 Airborne Infectious Isolation Room Exhaust Systems. Airborne infectious isolation
room exhaust systems serving AII rooms or combination AII/PE rooms shall not be used for
energy recovery.
Exception to 6.8.2: Airborne infectious isolation room exhaust systems serving AII rooms
or combination AII/PE rooms may be served by an energy recovery system where the
supply airstream components and the exhaust airstream components are fully separated
by an air gap of adequate distance to prevent cross-contamination that is open to the
atmosphere (e.g., run-around pumped coils).
6.8.3 Energy Recovery Systems with Leakage Potential. If energy recovery systems with
leakage potential are used, they shall be arranged to minimize the potential to transfer exhaust
air directly back into the supply airstream. Energy recovery systems with leakage potential
shall be designed to have no more than 5% of the total supply airstream consisting of exhaust
air. Energy recovery systems with leakage potential shall not be used from these exhaust airstream sources: emergency department waiting rooms, triage, emergency department decontamination, radiology waiting rooms, darkroom, bronchoscopy sputum collection and
pentamidine administration, laboratory fume hood and other directly ducted laboratory equipment exhaust, waste anesthesia gas disposal, autopsy, nonrefrigerated body holding, endoscope
cleaning, central medical and surgical supply soiled or decontamination room, laundry general,
hazardous material storage, dialyzer reprocessing room, nuclear medicine hot lab, nuclear
medicine treatment room, and any other space identified by the AHJ or the infection control
risk assessment (ICRA) team.
Exception to 6.8.3: Energy recovery systems that comply with the leakage and carryover
limitations of ASHRAE Standard 62.1 1 shall be permitted in all nonsurgical spaces
designed solely for outpatient use.
6.9 Insulation and Duct Lining
a. Pipes, ducts, and other surfaces within the building whose surface temperatures are
expected to fall below the surrounding dew-point temperature shall be insulated to prevent
condensation and provided with an exterior vapor barrier. A vapor barrier is not required
for insulation materials that do not absorb or transmit moisture.
b. Existing insulation and duct lining accessible during a renovation project shall be
inspected, repaired, and/or replaced as appropriate.
c. For spaces requiring a HEPA filter or minimum MERV-14 or higher filter, duct lining shall
not be used in ductwork located downstream of filters. Duct lining that is impervious, or
with an impervious cover, may be allowed in terminal units, sound attenuators, and air distribution devices downstream of filters. This lining and cover shall be factory installed.
d. Duct lining shall not be installed within 15 ft (4.57 m) downstream of humidifiers.
7. SPACE VENTILATION—INPATIENT SPACES
The ventilation requirements of this standard are minimums that provide control of environmental comfort, asepsis, and odor in inpatient spaces. However, because they are minimum
requirements, and because of the diversity of the population and variations in susceptibility and
sensitivity, these requirements do not provide assured protection from discomfort, airborne
transmission of contagions, and odors.
7.1 General Requirements. The following general requirements shall apply for space ventilation:
a. Spaces shall be ventilated according to Table 7-1.
ANSI/ASHRAE/ASHE Standard 170-2021
13
14
ANSI/ASHRAE/ASHE Standard 170-2021
Positive
Positive
NR
NR
NR
Positive
Laser eye room (FGI Table T2.2-1)
Neonatal intensive care (FGI 2.2–2.8)
Newborn nursery (FGI 2.2–2.10.3.1)
Nourishment area or room (FGI 2.1–2.8.9)
Nursery workroom (FGI 2.2–2.10.8.5)
Operating room (FGI 2.2–3.3.3) (m), (o)
20
NR
NR
6
2
4
NR
NR
NR
NR
NR
NR
NR
Yes (q)
NR
Yes (q)
Yes
NR
NR
N/R
Yes
Yes
NR
Yes
Yes
2
6
6
15
6
6
6
12
15
12
12
6
6
6
12
10
20
12
10
Minimum
Total ach
All Room Air
Exhausted
Directly to
Outdoors (j)
NR
2
2
3
2
2
2
2
3
2
2
2
2
2
2
NR
4
2
NR
Minimum
Outdoor
ach
Informative Notes: (1) NR = no requirement; (2) FGI paragraph numbers are shown in parentheses in the “Function of Space” column.
NR
Negative
Emergency department public waiting area
(FGI 2.2–3.1.2.4 & 2.2-3.1.3.4)
Labor/delivery/recovery/postpartum (LDRP)
(FGI 2.2–2.9.3) (s)
Negative
Emergency department human decontamination
(FGI 2.2–3.1.3.6[8])
NR
NR
Emergency department exam/treatment room
(FGI 2.2–3.1.2.6 & 2.2–3.1.3.6) (p)
Labor/delivery/recovery (LDR) (FGI 2.2–2.9.3) (s)
NR
Critical care patient care station (FGI 2.2–2.6.2)
NR
N/R
Continued care nursery (FGI 2.2–2.10.3.2)
Intermediate care patient room (FGI 2.2–2.5) (s)
Positive
Combination AII/PE room (FGI 2.2–2.2.4.5)
Negative
(e)
Combination AII/PE anteroom (FGI 2.2–2.2.4.5)
Emergency service triage area (FGI 2.2–3.1.3.3)
Positive
Cesarean Delivery room (FGI 2.2–2.9.11.1) (m), (o)
Positive
Negative
AII room (FGI 2.1–2.4.2) (u)
Emergency department trauma/resuscitation room
(FGI 2.2–3.1.3.6[4]) (c)
(e)
Pressure
Relationship
to Adjacent
Areas (n)
AII anteroom (FGI 2.1–2.4.2.3) (u)
NURSING UNITS AND OTH & ER PATIENT CARE AREAS
Function of Space (ee)
Table 7-1 Design Parameters—Inpatient Spaces
No
No
NR
No
No
No
NR
NR
NR
NR
No
NR
No
NR
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes (ff)
Yes
Yes (ff)
Yes (ff)
Yes (ff)
Yes
Yes
No
No
Yes
Yes
Yes
MERV-16 (hh)
MERV-8
MERV-8
MERV-14
MERV-14
MERV-14
MERV-14
MERV-14
MERV-14
MERV-8
MERV-14
MERV-8
MERV-14
MERV-14
MERV-14
MERV-14
HEPA
HEPA
MERV-16
MERV-14
MERV-8
Air
Recirculated by
Means of Room Unoccupied Minimum Filter
Units (a)
Turndown Efficiencies (cc)
20–60
Max 60
NR
30–60
30–60
20–60
Max 60
Max 60
Max 60
Max 60
20–60
Max 65
NR
Max 60
30–60
30–60
Max 60
NR
20–60
Max 60
NR
Design
Relative
Humidity (k),
%
68–75/20–24
72–78/22–26
NR
72–78/22–26
72–78/22–26
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
NR
70–75/21–24
70–75/21–24
72–78/22–26
70-75/21-24
NR
68–75/20–24
70–75/21–24
NR
Design
Temperature (l),
°F/°C
ANSI/ASHRAE/ASHE Standard 170-2021
15
NR
NR
Negative
(e)
NR
Positive
Positive
Negative
NR
NR
NR
Positive
Patient care area corridor
Patient room (FGI 2.1–2.3.2)
Patient toilet room (FGI 2.1–2.3.5 & 2.1–2.3.6)
PE anteroom (FGI 2.2–2.2.4.4) (t)
Phase I PACU and Phase II recovery
(FGI 2.1–3.4.4 & 2.1–3.4.5)
Procedure room (Table T2.2-1) (o), (d)
Protective environment room (FGI 2.2–2.2.4.4) (t)
Radiology waiting rooms (FGI 2.2–3.4.10.1)
Seclusion room (FGI 2.1–2.4.3)
Sterile processing room (FGI 2.2–3.3.6.15)
Treatment room (FGI 2.2–3.1.2.6) (p)
Wound intensive care (burn unit)
NR
Seclusion room (FGI 2.1–2.4.3 & 2.2–2.12.4.3)
3
4
2
NR (jj)
Positive
Negative
Class 2 imaging room (FGI 2.2–3.4.1.2 & Table 2.2-2) (d), (p)
Class 3 imaging room (FGI 2.2–3.4.1.2 & Table 2.2-2) (m), (o) Positive
NR
Class 1 imaging room (FGI 2.2–3.4.1.2 & Table 2.2-2)
Dialysis treatment area (FGI 2.2–3.10.2)
Dialyzer reprocessing room (FGI 2.2–3.10.8.16)
10 (bb)
6
20
15
6
12
2
2
6
6
6
4 (y)
12
12
15
6
10
10
4 (y)
2
20
Minimum
Total ach
Yes
NR
NR
NR
NR
Yes
NR
NR
NR
NR
NR
NR
Yes (q), (w)
NR
NR
NR
NR
Yes
NR
NR
NR
All Room Air
Exhausted
Directly to
Outdoors (j)
Informative Notes: (1) NR = no requirement; (2) FGI paragraph numbers are shown in parentheses in the “Function of Space” column.
NR
2
Negative
2
4
2
2
2
2
2
2
2
3
2
NR
NR
2
NR
4
Minimum
Outdoor
ach
Bronchoscopy, sputum collection, and pentamidine
administration (FGI 2.2–3.9.2) (n), (x)
DIAGNOSTIC AND TREATMENT
NR
Patient bedroom, resident room (FGI 2.2–2.12.2 & 2.5–2.2.2)
BEHAVIORAL AND MENTAL HEALTH FACILITIES (k)
Positive
Operating/surgical cystoscopic rooms (FGI 2.2–3.4 &
Table T2.2-2; also see Class 3 Imaging) (m), (o)
Function of Space (ee)
Pressure
Relationship
to Adjacent
Areas (n)
Table 7-1 Design Parameters—Inpatient Spaces (Continued)
Yes
Yes (ff)
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes (ff)
No
Yes
Yes
No
Yes (ff)
Yes
Yes
Yes
NR
No
No
NR
No
NR
NR
No
NR
No
NR
NR
No
No
No
No
No
NR
NR
No
MERV-8
MERV-8
MERV-16 (hh)
MERV-14
MERV-8
MERV-14
MERV-8
MERV-8
HEPA
MERV-8
MERV-8 (gg)
MERV-14
MERV-8
HEPA
MERV-14
MERV-14
HEPA
MERV-8
MERV-14
MERV-14
MERV-16
Air
Recirculated by
Means of Room Unoccupied Minimum Filter
Units (a)
Turndown Efficiencies (cc)
NR
NR
20–60
Max 60
Max 60
NR
NR
NR
40–60
20–60
NR
Max 60
Max 60
Max 60
20–60
20–60
NR
NR
Max 60
NR
20–60
Design
Relative
Humidity (k),
%
NR
72–78/22–26
68–75/21–24
70–75/21–24
72–78/22–26
68–73/20–23
NR
NR
70–75/21–24
70–75/21–24
NR
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
NR
NR
70–75/21–24
NR
68–75/20–24
Design
Temperature (l),
°F/°C
16
ANSI/ASHRAE/ASHE Standard 170-2021
NR
Negative
Negative
NR
Negative
Negative
NR
NR
General examination room (FGI 2.1–3.2)
Hydrotherapy (FGI 2.1–8.4.3.9)
Instrument processing room (FGI 2.2–3.11.4)
Medication room (FGI 2.1–2.8.8.2[1])
Nuclear medicine hot lab (FGI 2.2–3.4.8.22)
Physical therapy (FGI 2.2–2.13.8.16 & 2.6–3.1)
Special examination room (aa)
Treatment room (FGI 2.2–3.1.2.4)
2
2
NR
NR
Negative
Negative
Negative
Negative
Negative
Negative
Positive
Negative
Food and supply storage (FGI 2.1–4.3.8.13)
Food preparation areas (FGI 2.1–4.3.2) (i)
Laboratory work area, bacteriology (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, biochemistry (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, cytology (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, general (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, glasswashing (FGI 2.1–4.1.2) (f)
Laboratory work area, histology (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, media transfer (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, microbiology (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, nuclear medicine (FGI 2.1–4.1.2) (f), (v) Negative
6
6
4
6
10
6
6
6
6
10
2
10
10
6
6
6
6
4
10
6
4
6
4
Minimum
Total ach
Yes
Yes
NR
Yes
Yes
NR
Yes
Yes
Yes
NR
NR
Yes
Yes
NR
NR
NR
Yes
NR
Yes
NR
NR
NR
NR
All Room Air
Exhausted
Directly to
Outdoors (j)
Informative Notes: (1) NR = no requirement; (2) FGI paragraph numbers are shown in parentheses in the “Function of Space” column.
2
2
2
2
2
2
2
2
NR
Negative
NR
NR
2
2
2
NR
2
2
2
2
2
2
Minimum
Outdoor
ach
Environmental services room (FGI 2.1–2.8.14)
Bedpan room (FGI 2.1–2.8.12.2 & 2.1–5.1.3.3)
Negative
NR
Gastrointestinal endoscopy procedure room (FGI 2.2–3.11.2 &
Table 2.2-1) (x)
PATIENT SUPPORT FACILITIES
NR
ECT procedure room (FGI 2.2–2.12.4.1 & 2.5–3.4)
Function of Space (ee)
Pressure
Relationship
to Adjacent
Areas (n)
Table 7-1 Design Parameters—Inpatient Spaces (Continued)
NR
NR
NR
NR
NR
NR
NR
NR
NR
No
No
No
No
NR
NR
NR
No
NR
No
NR
NR
No
NR
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
Yes
Yes
Yes
Yes (ff)
Yes
No
Yes
Yes
Yes
Yes
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-14 (ii)
MERV-8
MERV-8
MERV-8
MERV-8 (gg)
MERV-8
MERV-8
MERV-8
MERV-8
Air
Recirculated by
Means of Room Unoccupied Minimum Filter
Units (a)
Turndown Efficiencies (cc)
72–80/22–27
70–75/21–24
70–75/21–24
Max 65
Max 60
Max 60
72–78/22–26
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
NR
70–75/21–24
70–75/21–24
70–75/21–24
NR
NR
NR
NR
NR
NR
NR
NR
NR
70–75/21–24
72–78/22–26
NR
NR
NR
NR
NR
70–75/21–24
NR
NR
70–75/21–24
Max 60
72–80/22–27
NR
NR
70–75/21–24
Max 60
NR
68–73/20–23
72–78/22–26
Design
Temperature (l),
°F/°C
20–60
Max 60
Design
Relative
Humidity (k),
%
ANSI/ASHRAE/ASHE Standard 170-2021
17
Negative
Negative
Positive
Negative
Negative
Laboratory work area, serology (FGI 2.1–4.1.2) (f), (v)
Laboratory work area, sterilizing (FGI 2.1–4.1.2) (f)
Pharmacy Services: Pharmacy Areas (FGI 2.1–4.2.2) (b)
Toilet room (FGI 2.1–2.9.2)
Warewashing (FGI 2.1–4.3.4) (r)
Negative
Negative
Regulated waste holding spaces (FGI 2.1–5.4.1.3)
Toilet (FGI 2.1–2.9.2)
Positive
Negative
Clean workroom (FGI 2.1–2.8.11.2)
Soiled workroom or soiled holding (FGI 2.1–2.8.12)
2
2
NR
10
NR
NR
10
10
10
10
10
10
2
12
4
6
4
NR
10
4
10
6
6
Minimum
Total ach
Yes
NR
NR
Yes
Yes
Yes
Yes
Yes
Yes
NR
Yes
NR
Yes
NR
Yes
Yes
NR
Yes
Yes
Yes
All Room Air
Exhausted
Directly to
Outdoors (j)
Informative Notes: (1) NR = no requirement; (2) FGI paragraph numbers are shown in parentheses in the “Function of Space” column.
Positive
Clean supply room (FGI 2.1–2.8.11.3)
SUPPORT AREAS FOR NURSING UNITS AND OTHER PATIENT CARE AREAS
NR
NR
NR
2
Negative
Negative
Laundry, processing room (FGI 2.1–5.2.2.1)
2
Nonrefrigerated body holding room (FGI 2.1–5.7.3) (h)
Negative
Hazardous material storage (FGI 2.1–5.4)
NR
NR
Positive
Clean linen storage room (FGI 2.1–2.8.13.1 & 2.1–5.2.2.1[3])
Linen and refuse chute room (FGI 2.1–5.2.8.1[2] & 2.1–5.4.1.4) Negative
Negative
Autopsy room (FGI 2.1–5.7.2.2)
2
2
Sterile storage room (clean/sterile medical/ surgical supplies)
(FGI 2.1–5.1.2.2[4]) (z)
OTHER GENERAL SUPPORT FACILITIES
2
Soiled workroom/decontamination room (FGI 2.1–5.1.2.2[2]) (z) Negative
Positive
2
NR
NR
2
2
2
2
Minimum
Outdoor
ach
Positive
Clean assembly/workroom (FGI 2.1–5.1.2.2[3]) (z)
GENERAL SUPPORT FACILITIES: STERILE PROCESSING
Negative
Laboratory work area, pathology (FGI 2.1–4.1.2) (f), (v)
Function of Space (ee)
Pressure
Relationship
to Adjacent
Areas (n)
Table 7-1 Design Parameters—Inpatient Spaces (Continued)
No
NR
NR
No
No
No
No
No
No
NR
No
NR
No
No
No
No
NR
NR
NR
NR
No
Yes
Yes
Yes
No
No
No
No
No
Yes
No
No
No
No
Yes
Yes
Yes
Yes
Yes
No
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8 (gg)
MERV-8
MERV-8 (gg)
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
Air
Recirculated by
Means of Room Unoccupied Minimum Filter
Units (a)
Turndown Efficiencies (cc)
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
Max 60
NR
Max 60
NR
NR
Max 60
NR
NR
NR
Design
Relative
Humidity (k),
%
NR
NR
NR
NR
NR
70–75/21–24
NR
NR
NR
72–78/22–26
68–75/20–24
Max 75/24
60–73/16–23
68–73/20–23
NR
72–78/22–26
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
Design
Temperature (l),
°F/°C
Normative Notes for Table 7-1:
a. Except where indicated by a “No” in this column, recirculating room HVAC units (with heating or cooling coils)
are acceptable for providing that portion of the minimum total air changes per hour that is permitted by Section 7.1
(subparagraph [a][5]). Because of the cleaning difficulty and potential for buildup of contamination, recirculating
room units shall not be used in areas marked “No.” Recirculating devices with high-efficiency particulate air
(HEPA) filters shall be permitted in existing facilities as interim, supplemental environmental controls to meet
requirements for the control of airborne infectious agents. The design of either portable or fixed systems should
prevent stagnation and short circuiting of airflow. The design of such systems shall also allow for easy access for
scheduled preventative maintenance and cleaning.
b. Pharmacy compounding areas may have additional air changes and differential pressure requirements beyond the
minimum of this table, depending on the type of pharmacy, the regulatory requirements (which may include adoption of USP-795, USP-797, and USP-800), the associated level of risk of the work, and the equipment used in the
spaces. Minimum efficiency of filters for any space where compounding occurs shall be determined by USP 795 7,
USP 797 8, or USP 800 9, as applicable.
c. The term trauma/resuscitation room as used herein is a first-aid room and/or emergency department room used for
general initial treatment of accident victims. The OR within the trauma center that is routinely used for emergency
surgery is considered to be an OR by this standard.
d. Pressure relationships need not be maintained when the room is unoccupied.
e. See Section 7.2.1 for AII ventilation requirements, including pressure relationship requirements, and Section 7.2.2
for PE ventilation requirements, including pressure relationship requirements.
f. Higher ventilation rates above the total ach listed shall be used when dictated by the laboratory program requirements and the hazard level of the potential contaminants in each laboratory work area. Lower total ach ventilation
rates shall be permitted when a hazard assessment, performed as part of an effective laboratory ventilation management plan per AIHA/ASSE Z9.5 3, determines that either (1) acceptable exposure concentrations in the laboratory
work area can be achieved with a lower minimum total ach ventilation rate than is listed in Table 7-1 or (2) a
demand control approach with active sensing of contaminants or appropriate surrogates is used as described in
ASHRAE Handbook—HVAC Applications10, Chapter 16, “Laboratories.”
g. Not used.
h. A nonrefrigerated body holding room is applicable only to facilities that do not perform autopsies on-site and use
the space for short periods while waiting for the body to be transferred.
i. Not used.
j. In some areas with potential contamination and/or odor problems, exhaust air shall be discharged directly to the
outdoors and not recirculated to other areas. Individual circumstances may require special consideration for air
exhausted to the outdoors. To satisfy exhaust needs, constant replacement air from the outdoors is necessary when
the system is in operation.
k. The relative humidity (RH) ranges listed are the minimum and/or maximum allowable at any point within the
design temperature range required for that space.
l. Systems shall be capable of maintaining the rooms within the range during normal operation. Lower or higher temperature shall be permitted when occupants’ comfort and/or medical conditions require those conditions.
m. National Institute for Occupational Safety and Health (NIOSH) criteria documents 11 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 used.
(Informative Note: Refer to NFPA 99 [2021] for other requirements.)
n. If pressure-monitoring device alarms are installed, allowances shall be made to prevent nuisance alarms. Short-term
excursions from required pressure relationships shall be allowed while doors are moving or temporarily open. Simple visual methods such as smoke trail, ball-in-tube, or flutterstrip shall be permitted for verification of airflow
direction.
o. Surgeons or surgical procedures may require room temperatures, ventilation rates, humidity ranges, and/or air distribution methods that exceed the minimum indicated ranges.
p. Treatment rooms used for bronchoscopy shall be treated as bronchoscopy rooms. Treatment rooms used for procedures with nitrous oxide shall contain provisions for exhausting anesthetic waste gases.
q. In a recirculating ventilation system, HEPA filters shall be permitted instead of exhausting the air from these spaces
to the outdoors, provided that the return air passes through the HEPA filters before it is introduced into any other
spaces. The entire minimum total air changes per hour of recirculating airflow shall pass through HEPA filters.
When these areas are open to larger, nonwaiting spaces, the exhaust air volume shall be calculated based on the
seating area of the waiting area. (Informative Note: The intent here is to not require the volume calculation to
include a very large space [e.g., an atrium] just because a waiting area opens onto it.)
r. Exhaust rate shall meet or exceed local requirements.
s. For intermediate care, labor/delivery/recovery rooms, and labor/delivery/recovery/postpartum rooms, four total ach
shall be permitted when supplemental heating and/or cooling systems (radiant heating and cooling, baseboard heating, etc.) are used.
18
ANSI/ASHRAE/ASHE Standard 170-2021
Normative Notes for Table 7-1 (continued):
t. The protective environment airflow design specifications protect the patient from common environmental airborne infectious microbes (i.e., Aspergillus spores). Recirculation HEPA filters shall be permitted to increase the
equivalent room air exchanges; however, the outdoor air changes are still required. Constant-volume airflow is
required for consistent ventilation for the protected environment. The pressure relationship to adjacent areas shall
remain unchanged if the protective environment (PE) room is used as a normal patient room. Rooms with reversible airflow provisions for the purpose of switching between PE and AII functions shall not be permitted.
u. The AII room described in this standard shall be used for isolating the airborne spread of infectious diseases, such
as measles, varicella, or tuberculosis. Supplemental recirculating devices using HEPA filters shall be permitted to
recirculate air within the AII room to increase the equivalent room air exchanges; however, the minimum outdoor
air changes of Table 7-1 are still required. When the AII room is not used for airborne infection isolation, the pressure relationship to adjacent areas, when measured with the door closed, shall remain unchanged, and the minimum total air change rate shall be 4 ach. Turndown of minimum air changes for the AII anteroom shall be based
around the use of the associated AII room(s).
v. Room temperature ranges that exceed the minimum indicated range shall be permitted if required by the laboratory
program or laboratory equipment.
w. The requirement that all room air be exhausted directly to outdoors applies only to radiology waiting rooms programmed to hold patients who are waiting for chest x-rays for diagnosis of respiratory disease.
x. If the planned space is designated in the organization’s operational plan to be used for both bronchoscopy and gastrointestinal endoscopy, the design parameters for “bronchoscopy, sputum collection, and pentamidine administration” shall be used.
y. For single-bed patient rooms using Group D diffusers, a minimum of six total ach shall be provided and calculated
based on the volume from finished floor to 6 ft (1.83 m) above the floor.
z. See AAMI Standard ST79 12 for additional information for these spaces.
aa. Examination rooms programmed for use by patients with undiagnosed gastrointestinal symptoms, undiagnosed
respiratory symptoms, or undiagnosed skin symptoms.
bb. Lower total ach ventilation rates shall be permitted when use of the ASHRAE Standard 62.1 1, Section 6.5,
“Exhaust Ventilation,” Performance Compliance Path determines that concentration of the contaminants of concern is lower than the corresponding concentration of interest. In addition to other contaminants of concern
required by Standard 62,1 Section 6.5.2, the following contaminants of concern shall be considered for the space
and maintained not greater than the concentration level indicated: hydrogen peroxide 1 ppm; glutaraldehyde 0.05
ppm; ethyl alcohol 1000 ppm; isopropyl alcohol 400 ppm. (Informative Note: Listed concentrations of interest
were determined by ACGIH [2001]; see Informative Appendix E.)
cc. Table entries are the minimum filter efficiencies required for the space. Refer to Section 6.4 of this document for
further clarification of filtration requirements. The minimum efficiency reporting value (MERV) is based on the
method of testing described in ASHRAE Standard 52.2 4.
dd. As an alternative to the requirement for HEPA filters in Filter Bank No. 2, MERV-14 rated filters may be used in
Filter Bank No. 2 if a tertiary terminal HEPA filter is provided for this space. (Informative Note: HEPA filters are
those filters that remove at least 99.97% of 0.3 micron sized particles at the rated flow in accordance with the testing methods of IEST RP-CC001.3 [2005] in Informative Appendix E).
ee. Informative Note: Parenthetic notations following a space name are paragraph references to the relevant FGI
Guidelines (FGI 2018a, 2018b, 2018c) in Informative Appendix E. These paragraph references are provided to the
user to aid in the application of design requirements.
ff. If this space uses unoccupied turndown it shall include time-delay controls such that turndown does not occur for
the first 20 minutes after the space becomes unoccupied. (Informative Note: The 20 minute delay approximates the
time required for 90% reduction in airborne contamination at 6 ach, assuming perfect mixing.)
gg. Minimum MERV-14 filters shall be required for spaces where sterile equipment is packed into sterile packages.
Spaces where sterile products are stored but not packed shall not be required to have MERV-14 filters.
hh. See also Section 7.4.1(c).
ii. A minimum MERV-8 filter may be utilized for this space in lieu of a minimum MERV-14 filter if all room air is
exhausted directly to the outdoors and the pressure relationship to adjacent areas is kept negative. If a filter rated
less than MERV-14 is utilized, the space shall be considered “Negative” with regards to the table and must comply
with all other requirements for negative spaces within the standard.
jj. Negative pressure is required if open mixing of isotopes or gaseous studies are performed as a part of nuclear treatment procedures within the imaging room. (Informative Note: Open mixing of isotopes is typically performed in
the hot lab.)
ANSI/ASHRAE/ASHE Standard 170-2021
19
1. Design of the ventilation system shall provide air movement that 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 shall not compromise the pressure balancing relationships or the minimum air changes required by the table.
2. The ventilation requirements in this table are intended to provide for comfort as well as
for asepsis and odor control in spaces of a health care facility that directly affect patient
care. For spaces not specifically listed here, ventilation requirements shall be that of
functionally equivalent spaces in the table. If no functionally equivalent spaces exist in
the table, ventilation requirements shall be obtained from ASHRAE Standard 62.1 1 in
the absence of other codes or standards that govern those space ventilation rate requirements. Where spaces with prescribed rates in both Standard 62.1 and Table 7-1 of this
standard exist, the higher of the two air change rates shall be used.
3. For design purposes, the minimum number of total air changes indicated shall be either
supplied for positive pressure rooms or exhausted for negative pressure rooms. Spaces
that are required in Table 7-1 to be at a negative pressure relationship and that are not
required to be exhausted shall use the supply airflow rate to compute the minimum total
air changes per hour required. Except where indicated by a “No” in the “Unoccupied
Turndown” column, the number of air changes shall be permitted to be reduced and the
temperature and design relative humidity altered when the space is unoccupied, provided that the required pressure relationship to adjoining spaces is maintained while the
space is unoccupied and that the minimum number of air changes, temperature, and
design relative humidity indicated are reestablished anytime the space becomes occupied (Informative Note: see Appendix A for additional information). Controls intended
to switch the required pressure relationships between spaces from positive to negative,
and vice versa, shall not be permitted. Air change rates in excess of the minimum values
are expected in some cases in order to maintain room temperature and design relative
humidity conditions based on the space cooling or heating load.
4. The entire minimum outdoor air changes per hour required by Table 7-1 for the space
shall meet the filtration requirements of Section 6.4.
5. For spaces where Table 7-1 permits air to be recirculated by room units, the portion of
the minimum total air changes per hour required for a space that is greater than the minimum outdoor air changes per hour required component may be provided by recirculating room HVAC units. Such recirculating room HVAC units shall
i. not receive nonfiltered, nonconditioned outdoor air;
ii. serve only a single space; and
iii. provide a minimum MERV 8 filter for airflow passing over any surface that is
designed to condense water. This filter shall be located upstream of any such cold
surface so that all of the air passing over the cold surface is filtered.
6. For air-handling systems serving multiple spaces, system minimum outdoor air quantity
shall be calculated using one of the following methods:
i. System minimum outdoor air quantity for an air-handling system shall be calculated
as the sum of the individual space requirements as defined by this standard.
ii. System minimum outdoor air quantity shall be calculated by the Ventilation Rate
Procedure (multiple zone formula) of ASHRAE Standard 62.1 1. The minimum outdoor air change rate listed in this standard shall be interpreted as the zone outdoor
airflow (Voz) for purposes of this calculation.
7. Unless a higher ventilation rate is stipulated in Table 7-1 or elsewhere in this standard,
wherever anesthetic gases are administered outside of an operating room, procedure
room, or Class 2 and Class 3 imaging rooms, ventilation shall be provided at a minimum
rate of 2 outdoor ach and 6 total ach. (Informative Notes: [1] Refer to NFPA 99 [2021]
in Informative Appendix E for WAGD piping and gas scavenging requirements. [2]
“Anesthetic gases” commonly refers to nitrous oxide and xenon but may also include
halogenated volatile anesthetic agents such as desflurane, sevoflurane, and isoflurane.)
b. Air filtration for spaces shall comply with Table 7-1.
c. Supply air outlets for spaces shall comply with Table 6-2.
20
ANSI/ASHRAE/ASHE Standard 170-2021
d. In AII rooms, protective environment rooms, wound intensive care units (burn units), and
operating and procedure rooms, heating with supply air or radiant panels that meet the
requirements of Section 6.5.3 shall be provided.
e. In a building that contains a mixture of spaces programmed for outpatient care as well as
spaces programmed for inpatient care, the outpatient care spaces shall be designed in
accordance with Tables 8-1 and 8-2, and the inpatient care spaces shall be designed in
accordance with Table 7-1.
7.2 Additional Room-Specific Requirements
7.2.1 Airborne Infection Isolation (AII) Rooms. Ventilation for AII rooms shall meet the
following requirements whenever an infectious patient occupies the room:
a. Each AII room shall comply with requirements of Tables 6-2 and 7-1. AII rooms shall have
a permanently installed device and/or mechanism to constantly monitor the differential air
pressure between the room (when occupied by patients with a suspected airborne infectious
disease) and the corridor, whether or not there is an anteroom. A local visual means shall be
provided to indicate whenever negative differential pressure is not maintained.
b. All exhaust air from the AII rooms, associated anterooms, and associated toilet rooms shall
be discharged by one of the following methods:
1. Discharged directly to the outdoors without mixing with exhaust air from any other
non-AII room or general exhaust system.
2. Discharged into the general exhaust stream, provided the AII exhaust air first passes
through a HEPA filter. The HEPA filter, including ductwork and fans, shall be under
negative pressure (suction side) for any supplemental fan used to account for filter pressure drop, and all exhaust ductwork shall be kept under negative pressure in accordance
with Section 6.3.2.1. (Informative Note: If fans are used/needed due to static pressure
drop of HEPA filtration, consideration should be given to the fan operation being interlocked with the general exhaust system fan. Alarms for filter loading and fan failure
should be considered.)
c. Exhaust air grilles or registers in the patient room shall be located directly above the patient
bed, on the ceiling or on the wall near the head of the bed, unless it can be demonstrated
that such a location is not practical.
d. The room envelope shall be sealed to provide a minimum differential pressure of 0.01 in. of
water (2.5 Pa) across the envelope.
e. Differential pressure between AII rooms and adjacent spaces that are not AII rooms shall
be a minimum of –0.01 in. of water (–2.5 Pa). Spaces such as the toilet room and the anteroom (if present) that are directly associated with the AII room and open directly into the
AII room are not required to be designed with a minimum pressure difference from the AII
room but are still required to maintain the pressure relationships to adjacent areas specified
in Table 7-1.
f. When an anteroom is provided, the pressure relationships shall be as follows:
1. The AII room shall be at a negative pressure with respect to the anteroom.
2. The anteroom shall be at a negative pressure with respect to the corridor.
7.2.2 Protective Environment (PE) Rooms. Ventilation for PE rooms shall meet the following requirements:
a. The room envelope shall be sealed to provide a minimum differential pressure of 0.01 in. of
water (2.5 Pa) across the envelope.
b. Each PE room shall comply with the requirements of Tables 6-2 and 7-1. When occupied by
patients requiring a protective environment, PE rooms shall have a permanently installed
device and/or mechanism to constantly monitor the differential air pressure between the
room and the corridor, regardless of whether there is an anteroom. A local visual means shall
be provided to indicate whenever positive differential pressure is not maintained.
c. Air distribution patterns within the protective environment room shall conform to the following:
1. Supply air diffusers shall be located above the patient bed unless it can be demonstrated that such a location is not practical. Diffuser design shall limit air velocity at
ANSI/ASHRAE/ASHE Standard 170-2021
21
the patient bed to reduce patient discomfort. (Informative Note: See ASHRAE
[2017a] in Appendix E.)
2. Return/exhaust grilles or registers shall be located near the patient room door.
3. HEPA filters shall be located in the air terminal device.
Exception to 7.2.2(c): For common systems serving more than one protective environment space and where more than 75% of airflow serves protective environment spaces,
HEPA filters may be located in the air-handling unit (AHU) in a position downstream
of all cooling and heating equipment.
d. Differential pressure between PE rooms and adjacent spaces that are not PE rooms shall be
a minimum of +0.01 in. of water (+2.5 Pa). Spaces such as the toilet room and the anteroom
(if present) that are directly associated with the PE room and open directly into the PE
room are not required to be designed with a minimum pressure difference from the PE
room but are still required to maintain the pressure relationships to adjacent areas specified
in Table 7-1.
e. PE rooms retrofitted from standard patient rooms may be ventilated with recirculated air,
provided that air first passes through a HEPA filter and the room complies with Section
7.2.2(a) through 7.2.2(d).
f. When an anteroom is provided, the pressure relationships shall be as follows:
1. The PE room shall be at a positive pressure with respect to the anteroom.
2. The anteroom shall be at a positive pressure with respect to the corridor.
7.2.3 Combination Airborne Infectious Isolation/Protective Environment (AII/PE)
Rooms. Ventilation for AII/PE rooms shall meet the following requirements:
a. Supply air diffusers shall be located above the patient bed.
b. Exhaust grilles or registers shall be located near the patient room door.
c. The pressure relationship to adjacent areas for the required anteroom shall be one of the
following:
1. The anteroom shall be at a positive pressure with respect to both the AII/PE room and
the corridor or common space.
2. The anteroom shall be at a negative pressure with respect to both the AII/PE room and
the corridor or common space.
d. AII/PE rooms shall have two permanently installed devices and/or mechanisms to constantly monitor the differential air pressure. One device and/or mechanism shall monitor
the pressure differential between the AII/PE room and the anteroom. The second device
and/or mechanism shall monitor the pressure differential between the anteroom and the
corridor or common space. For each device and/or mechanism, a local visual means shall
be provided to indicate whenever differential pressure is not maintained.
7.3 Critical Care Units
7.3.1 Wound Intensive Care Units (Burn Units). Burn-unit patient rooms that require
humidifiers to comply with Table 7-1 shall be provided with individual humidity control.
7.4 Surgery Rooms
7.4.1 Operating Rooms (ORs), Operating/Surgical Cystoscopic Rooms, Caesarean
Delivery Rooms, and Class 3 Imaging Rooms. These rooms shall be maintained at a positive
pressure with respect to all adjoining spaces at all times. A pressure differential shall be maintained at a value of at least +0.01 in. of water (2.5 Pa). Each room shall have individual temperature control. These rooms shall be provided with a primary supply diffuser array that is
designed as follows:
a. The airflow shall be unidirectional, downwards, and the average velocity of the diffusers
shall be 25 to 35 cfm/ft2 (127 to 178 L/s/m2). The diffusers shall be concentrated to provide
an airflow pattern over the patient and surgical team. (Informative Note: For more information, see Memarzadeh and Manning [2002] and Memarzadeh and Jiang [2004] in Informative Appendix E.)
b. The coverage area of the primary supply diffuser array shall extend a minimum of 12 in.
(305 mm) beyond the footprint of the surgical table on each side. Within the portion of the
primary supply diffuser array that consists of an area encompassing 12 in. (305 mm) on
22
ANSI/ASHRAE/ASHE Standard 170-2021
each side of the footprint of the surgical table, no more than 30% of this portion of the primary supply diffuser array area shall be used for nondiffuser uses such as lights, gas columns, equipment booms, access panels, sprinklers, etc.
c. In operating rooms designated for orthopedic procedures, transplants, neurosurgery, or dedicated burn unit procedures, HEPA filters shall be provided.
d. In ORs or Class 3 imaging rooms designated for orthopedic procedures, transplants, neurosurgery, or dedicated burn unit procedures, HEPA filters shall be provided and located in
the air terminal device.
Additional supply diffusers shall be permitted within the room, outside of the primary supply diffuser array, to provide additional ventilation to the operating room to achieve the environmental requirements of Table 7-1 that relate to temperature, humidity, or a portion of the
required air change rates.
The room shall be provided with at least two low sidewall return or exhaust grilles spaced
at opposite corners or as far apart as possible, with the bottom of these grilles installed approximately 8 in. (203 mm) above the floor.
Exception to 7.4.1: In addition to the required low return (or exhaust) air grilles, such grilles
may be placed high on the walls.
7.4.2 Sterilization Rooms. Steam that escapes from a steam sterilizer shall be exhausted
using an exhaust hood or other suitable means. Ethylene oxide that escapes from a gas sterilizer shall be exhausted using an exhaust hood or other suitable means.
7.5 Support Spaces
7.5.1 Morgue and Autopsy Rooms. Ventilation for morgue and autopsy rooms shall meet
the following requirements:
a. Low sidewall exhaust grilles shall be provided unless exhaust air is removed through an
autopsy table designed for this purpose.
b. All exhaust air from autopsy, nonrefrigerated body holding, and morgue rooms shall be discharged directly to the outdoors without mixing with air from any other room or exhaust
system.
c. Differential pressure between morgue and autopsy rooms and any adjacent spaces that have
other functions shall be a minimum of –0.01 in. of water (–2.5 Pa).
7.5.2 Bronchoscopy
a. Differential pressure between bronchoscopy procedure and sputum induction rooms and any
adjacent spaces that have other functions shall be a minimum of –0.01 in. of water (–2.5Pa).
b. Local exhaust shall be provided for sputum collection procedures.
7.5.3 Medical/Anesthesia Gas Storage Rooms. Ventilation for medical/anesthesia gas storage rooms shall comply with NFPA 99 13.
7.5.4 Food preparation areas. Provide makeup air to kitchen exhaust systems as specified
in ASHRAE Standard 154 14. Kitchens with Type I hoods shall be designed to have a negative
pressure with respect to adjacent areas.
Informative Note: In some cases, excess exfiltration or infiltration to or from exit corridors compromises the exit corridor restrictions of NFPA 90A15 or the pressure requirements of
NFPA 96 16.
7.6 Behavioral and Mental Health Patient Areas. HVAC systems and related controls shall
be secured as called for in the patient safety risk assessment. All exposed equipment located
with these spaces shall have enclosures with rounded corners and tamper-resistant fasteners.
With the exception of HVAC room recirculating units, equipment shall be arranged such that
maintenance personnel are not required to enter patient care spaces for service, unless
approved by the AHJ when such arrangement is not possible. Seclusion, restraint, and observation rooms intended for behavioral and mental health patients shall use fully recessed, vandalresistant grilles with diffuser blades designed for ligature-resistant and anticontraband capability. Spaces intended for the care and treatment of inpatients who do not require acute medical
services shall comply with behavioral and mental health facilities in Table 7-1.
ANSI/ASHRAE/ASHE Standard 170-2021
23
8. SPACE VENTILATION—OUTPATIENT SPACES
The ventilation requirements of this standard are minimums that provide control of environmental comfort, asepsis, and odor in outpatient spaces. However, because they are minimum
requirements, and because of the diversity of the population and variations in susceptibility and
sensitivity, these requirements do not provide assured protection from discomfort, airborne
transmission of contagions, and odors.
8.1 Specialized Outpatient Facility Requirements. The following facility types shall comply with this section: outpatient surgical, endoscopy, infusion, renal dialysis, freestanding
emergency departments, and imaging facilities with Class 2 and 3 imaging rooms. The following general requirements shall apply for space ventilation:
a. Spaces shall be ventilated according to Table 8-1.
1. Design of the ventilation system shall provide air movement that 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 shall not compromise the pressure balancing relationships or the minimum air changes required by the table.
2. The ventilation requirements in this table are intended to provide for comfort as well as
for asepsis and odor control in spaces of a health care facility that directly affect patient
care. For spaces not specifically listed here, ventilation requirements shall be that of functionally equivalent spaces in the table. If no functionally equivalent spaces exist in the
table, ventilation requirements shall be obtained from ASHRAE Standard 62.1 1 in the
absence of other codes or standards that govern those space ventilation rate requirements. Where spaces with prescribed rates in both Standard 62.1 and Table 8-1 of this
standard exist, the higher of the two air change rates shall be used.
3. For design purposes, the minimum number of total air changes indicated shall be either
supplied for positive pressure rooms or exhausted for negative pressure rooms. Spaces
that are required in Table 8-1 to be at a negative pressure relationship and that are not
required to be exhausted shall utilize the supply airflow rate to compute the minimum
total air changes per hour required. For spaces that require a positive or negative pressure relationship, the number of air changes can be reduced when the space is unoccupied, provided that the required pressure relationship to adjoining spaces is maintained
while the space is unoccupied and that the minimum number of air changes indicated is
reestablished anytime the space becomes occupied. Controls intended to switch the
required pressure relationships between spaces from positive to negative, and vice
versa, shall not be permitted. Air change rates in excess of the minimum values are
expected in some cases in order to maintain room temperature and design relative
humidity conditions based on the space cooling or heating load. A night setback or
unoccupied mode (to maintain a temperature range of 55°F to 85°F [13°C to 30°C) with
a maximum of 65% design relative humidity) is permitted where pressurization is not
required and where facilities are closed and unoccupied for blocks of time such as
nights and weekends.
4. The entire minimum outdoor air changes per hour required by Table 8-1 for the space
shall meet the filtration requirements of Section 8.1.
5. For spaces where Table 8-1 permits air to be recirculated by room units, the portion of
the minimum total air changes per hour required for a space that is greater than the minimum outdoor air changes per hour required component may be provided by recirculating room HVAC units. Such recirculating room HVAC units shall
i. not receive nonfiltered, nonconditioned outdoor air;
ii. serve only a single space; and
iii. provide a minimum MERV 8 filter for airflow passing over any surface that is
designed to condense water. This filter shall be located upstream of any such cold
surface, so that all of the air passing over the cold surface is filtered.
6. For air-handling systems serving multiple spaces, system minimum outdoor air quantity
shall be calculated using one of the following methods:
i. System minimum outdoor air quantity for an air-handling system shall be calculated
as the sum of the individual space requirements as defined by this standard.
ii. System minimum outdoor air quantity shall be calculated by the Ventilation Rate
Procedure (multiple zone formula) of ASHRAE Standard 62.1 1. The minimum out24
ANSI/ASHRAE/ASHE Standard 170-2021
ANSI/ASHRAE/ASHE Standard 170-2021
25
Function of Space (f)
Negative
NR
Negative
Positive
Positive
NR
NR
NR
Positive
Negative
ED human decontamination (FGI 2.8–3.4.8)
ED exam/treatment room (FGI 2.8–3.4.2) (p)
ED public waiting area (FGI 2.8–6.2.3)
Operating room (FGI 2.1–3.2.3) (m), (o), (v), (gg)
Procedure room (FGI 2.1–3.2.2) (d), (o), (p)
Phase I recovery (PACU) (FGI 2.1–3.7.4)
Phase II recovery (FGI 2.1–3.7.5) (u)
Pre-procedure patient care (FGI 2.1–3.7.3) (t)
Trauma room (crisis or shock) (FGI 2.8–3.4.4) (bb)
Triage (FGI 2.8–6.2.2.2 & 6.2.2.3)
Positive
Positive
Negative
(e)
Negative
(e)
Positive
NR
NR
Negative
Negative
Negative
NR
Class 2 imaging room (FGI 2.1–3.5.2.4[1][b][ii]) (d), (p), (ff)
Class 3 imaging room (FGI 2.1–3.5.2.4[1][b][ii]) (m), (o), (ff)
Diagnostic imaging waiting (FGI 2.1–3.5.10.4) (g)
AII anteroom (FGI 2.1–3.3.2.3) (i)
AII room (FGI 2.1–3.3.2) (i)
PE anteroom (FGI 1.2–4.2.2.1[1]) (n) (w)
Protective environment room (FGI 1.2–4.2.2.1[1]) (n) (w)
Cancer treatment area (FGI 2.6–3.1)
Dialysis treatment area (FGI 2.10–3.2)
Dialyzer reprocessing room (FGI 2.10–3.8.12)
Bronchoscopy (FGI 2.1–3.2.2.1) (n) (x)
Instrument processing room (FGI 2.1–4.3.2.3)
Endoscopy procedure room (FGI 2.9–3.2) (h)
Informative Note: NR = no requirement
NR
Class 1 imaging room (FGI 2.1–3.5.2.4[1][b][i]) (ff)
DIAGNOSTIC AND TREATMENT
Positive
Delivery (Caesarean) (FGI 2.1–3.2.3) (m), (o), (v), (gg)
SURGERY AND EMERGENCY DEPARTMENT (ED)
Pressure
Relationship
to Adjacent
Areas (n)
Table 8-1 Design Parameters—Specialized Outpatient Spaces
2
2
2
NR
2
2
2
NR
2
NR
2
4
3
2
2
3
2
2
2
3
4
2
2
2
4
Minimum
Outdoor
ach
6
10
12
10
6
6
12
10
12
10
12
20
15
6
12
15
2
2
6
15
20
12
6
12
20
Minimum
Total ach
NR
Yes
Yes
Yes
NR
NR
NR
NR
Yes
Yes
Yes (q), (r)
NR
NR
NR
Yes (q)
NR
NR
NR
NR
NR
NR
Yes (q)
NR
Yes
NR
All Room Air
Exhausted
Directly
to Outdoors (j)
No
No
No
No
NR
NR
No
No
No
No
NR
No
No
NR
NR
No
NR
NR
No
No
No
NR
NR
No
No
Max 65
Max 60
NR
20–60
Max 60
Max 60
20–60
Max 60
Max 60
Max 60
20–60
MERV-8
MERV-8 (s)
MERV-14
MERV-8
MERV-8
MERV-8
HEPA
HEPA
MERV-8
MERV-8
MERV-8
Max 60
NR
NR
NR
NR
Max 60
Max 60
NR
Max 60
NR
Max 60
MERV-16 (dd) 20–60
MERV-14
MERV-8
MERV-8
MERV-14
MERV-8
MERV-8
MERV-8
MERV-14
MERV-16 (dd) 20–60
MERV-8
MERV-14 (cc)
MERV-14 (cc)
MERV-16 (dd) 20–60
Air
Recirculated by Minimum
Design
Means of
Filter
Relative
Room Units (a) Efficiencies (c) Humidity (k), %
68–73/20–23
NR
68–73/20–23
NR
72–78/22–26
70–75/21–24
70–75/21–24
NR
70–75/21–24
NR
70–75/21–24
68–75/20–24
70–75/21–24
72–78/22–26
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
68–75/20–24
70–75/21–24
70–75/21–24
NR
68–75/20–24
Design
Temperature (l),
°F/°C
26
ANSI/ASHRAE/ASHE Standard 170-2021
Negative
Negative
Positive
NR
Negative
Negative
Specialty IC exam room (FGI 2.1–3.2.1.3) (y)
Laboratory work room (FGI 2.1–4.1.2.1) (z)
Pharmacy/med prep (FGI 2.1–3.8.8.2 & 2.1–4.2.2) (b)
Laser eye room (FGI 2.1–3.2.2)
Nuclear medicine (see Section 8.7) (FGI 2.1–3.5.7)
Toilet or Toilet/Shower room (FGI 2.1–3.10.2)
Negative
Positive
Positive
Negative
Negative
Sterilizer equipment room (FGI 2.1–4.3.2.2)
Clean workroom (FGI 2.1–4.3.2.2.3)
Clean supply storage (FGI 2.1–4.3.2.2.4)
Supply receiving (FGI 2.1–4.3.2.4)
Decontamination room (FGI 2.1–4.3.2.2)
Negative
Positive
Negative
Negative
Laundry/linen processing (FGI 2.1–4.4.2.1)
Clean workroom or clean supply (FGI 2.1–3.8.11)
Regulated waste holding (FGI 2.1–5.2.1.3)
Soiled workroom or soiled holding (FGI 2.1–3.8.12)
Informative Note: NR = no requirement
Negative
Environmental services room (FGI 2.1–5.3.1)
SERVICE/SUPPORT SPACE
NR
One-room sterile processing (FGI 2.1–4.3.2.3)
STERILE PROCESSING (aa)
NR
Examination/observation (FGI 2.1–3.2.1)
DIAGNOSTIC AND TREATMENT (Continued)
Function of Space (f)
Pressure
Relationship
to Adjacent
Areas (n)
Table 8-1 Design Parameters—Specialized Outpatient Spaces
2
2
2
2
NR
2
NR
2
2
NR
2
NR
2
2
2
2
2
2
Minimum
Outdoor
ach
6
10
4
10
10
6
10
4
4
10
6
10
6
6
4
6
6
4
Minimum
Total ach
Yes
Yes
NR
Yes
Yes
Yes
Yes
NR
NR
Yes
NR
Yes
Yes
NR
NR
Yes
Yes
NR
All Room Air
Exhausted
Directly
to Outdoors (j)
No
No
NR
No
No
No
No
NR
No
No
No
No
No
No
NR
NR
NR
NR
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-14 (ee)
MERV-14 (ee)
MERV-8
MERV-14 (ee)
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
NR
NR
NR
NR
NR
NR
NR
Max 60
Max 60
NR
NR
NR
NR
Max 60
NR
NR
Max 60
Max 60
Air
Recirculated by Minimum
Design
Means of
Filter
Relative
Room Units (a) Efficiencies (c) Humidity (k), %
72–78/22–26
NR
NR
NR
NR
60–73/16–23
NR
72–78/22–26
60–73/16–23
NR
NR
NR
70–75/21–24
68–73/20–23
NR
70–75/21–24
70–75/21–24
70–75/21–24
Design
Temperature (l),
°F/°C
Normative Notes for Table 8-1:
a. Except where indicated by a “No” in this column, recirculating room HVAC units (with heating or cooling coils)
are acceptable for providing that portion of the minimum total air changes per hour that is permitted by Section 8.1
(subparagraph [a][5]). Because of the cleaning difficulty and potential for buildup of contamination, recirculating
room units shall not be used in areas marked “No.” Recirculating devices with high-efficiency particulate air
(HEPA) filters shall be permitted in existing facilities as interim, supplemental environmental controls to meet
requirements for the control of airborne infectious agents. The design of either portable or fixed systems should
prevent stagnation and short circuiting of airflow. The design of such systems shall also allow for easy access for
scheduled preventative maintenance and cleaning.
b. Pharmacy compounding areas may have additional air changes and differential pressure requirements beyond the
minimum of this table, depending on the type of pharmacy, the regulatory requirements (which may include
adoption of USP 795, USP 797, and USP 800), the associated level of risk of the work, and the equipment used in
the spaces. Minimum efficiency of filters for any space where compounding occurs shall be determined by USP
795 7, USP 797 8, or USP 800 9, as applicable.
c. Table entries are the minimum filter efficiencies required for the space. Refer to Section 6.4 of this document for
further clarification of filtration requirements. The minimum efficiency reporting value (MERV) is based on the
method of testing described in ASHRAE Standard 52.2 4.
d. Pressure relationships need not be maintained when the room is unoccupied.
e. See Section 7.2.1 for AII ventilation requirements, including pressure relationship requirements, and Section 7.2.2
for PE ventilation requirements, including pressure relationship requirements.
f. Informative Note: Parenthetic notations following a space name are paragraph references to the relevant FGI
Guidelines (FGI 2018a, 2018b, 2018c) in Informative Appendix E. These paragraph references are provided to the
user to aid in the application of design requirements.
g. These ventilation requirements only apply to waiting areas where the infection control risk assessment (ICRA)
determines that the diagnostic imaging waiting area requires special consideration to reduce the risk of airborne
infection transmission. If the ICRA does not have these special consideration provisions then the ventilation
requirements shall meet the provisions of ASHRAE Standard 62.1 1.
h. If the planned space is designated in the organization’s operational plan to be used for both bronchoscopy and gastrointestinal endoscopy, the design parameters for “bronchoscopy, sputum collection, and pentamidine administration” shall be used.
i. The AII room described in this standard shall be used for isolating the airborne spread of infectious diseases, such as
measles, varicella, or tuberculosis. Supplemental recirculating devices using HEPA filters shall be permitted in the
AII room to increase the equivalent room air exchanges; however, the minimum outdoor air changes of Table 8-1 are
still required. When the AII room is not used for airborne infection isolation, the pressure relationship to adjacent
areas, when measured with the door closed, shall remain unchanged, and the minimum total air change rate shall be
6 ach.
j. In some areas with potential contamination and/or odor problems, exhaust air shall be discharged directly to the
outdoors and not recirculated to other areas. Individual circumstances may require special consideration for air
exhausted to the outdoors. To satisfy exhaust needs, constant replacement air from the outdoors is necessary when
the system is in operation.
k. The relative humidity (RH) ranges listed are the minimum and/or maximum allowable at any point within the
design temperature range required for that space.
l. Systems shall be capable of maintaining the rooms within the range during normal operation. Lower or higher temperature shall be permitted when occupants’ comfort and/or medical conditions require those conditions.
m. National Institute for Occupational Safety and Health (NIOSH) criteria documents 11 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 used.
(Informative Note: Refer to NFPA 99 [2021] for other requirements.)
n. If pressure-monitoring device alarms are installed, allowances shall be made to prevent nuisance alarms. Short-term
excursions from required pressure relationships shall be allowed while doors are moving or temporarily open. Simple visual methods such as smoke trail, ball-in-tube, or flutterstrip shall be permitted for verification of airflow
direction.
o. Surgeons or surgical procedures may require room temperatures, ventilation rates, humidity ranges, and/or air distribution methods that exceed the minimum indicated ranges.
p. Treatment or procedure rooms used for bronchoscopy shall be treated as bronchoscopy rooms. Treatment or procedure rooms used for procedures with nitrous oxide shall contain provisions for exhausting anesthetic waste gases.
q. In a recirculating ventilation system, HEPA filters shall be permitted instead of exhausting the air from these spaces
to the outdoors, provided that the return air passes through the HEPA filters before it is introduced into any other
spaces. The entire minimum total air changes per hour of recirculating airflow shall pass through HEPA filters.
When these areas are open to larger, nonwaiting spaces, the exhaust air volume shall be calculated based on the
seating area of the waiting area. (Informative Note: The intent here is to not require the volume calculation to
include a very large space [e.g., an atrium] just because a waiting area opens onto it.)
r. The requirement that all room air be exhausted directly to outdoors applies only to radiology waiting rooms programmed to hold patients who are waiting for chest x-rays for diagnosis of respiratory disease.
ANSI/ASHRAE/ASHE Standard 170-2021
27
Normative Notes for Table 8-1 (continued):
s. Minimum MERV-14 filters shall be required for spaces where sterile equipment is packed into sterile packages.
Spaces where sterile products are stored but not packed shall not be required to have MERV-14 filters.
t. If anesthetic gases are administered in the area, the minimum total air changes shall be increased to 6.
u. If anesthetic gases are used during the preceding procedure, the minimum total air changes shall be increased to 6.
v. See Section 8.4.1 for ventilation requirements. The “Operating Room” designation includes surgical cystoscopic
rooms.
w. See Section 7.2.2 for ventilation requirements.
x. This space includes sputum collection and pentamidine administration. See Section 8.5.2.
y. Examination rooms (identified as “specialty infection control [IC] exam rooms”) programmed for use by patients
with undiagnosed gastrointestinal symptoms, undiagnosed respiratory symptoms, or undiagnosed skin symptoms.
z. This room is intended for basic blood and urine specimen testing and short-term storage only. Outpatient facilities
that provide the following specialized service spaces/rooms should consult Table 7-1 of this standard for ventilation
requirements: laboratory work areas, including the specialty lab services such as bacteriology, biochemistry, cytology, glasswashing, histology, media transfer, microbiology, nuclear medicine, pathology, serology and/or sterilizing.
aa. See AAMI Standard ST79 12 for additional information for these spaces.
bb. The term “trauma room,” as used herein, is a first-aid room and/or emergency department room used for general
initial treatment of accident victims. The operating room (OR) within the trauma center that is routinely used for
emergency surgery is considered to be an OR by this standard.
cc. A minimum MERV-8 filter may be utilized for this space in lieu of a minimum MERV-14 filter if all room air is
exhausted directly to the outdoors and the pressure relationship to adjacent areas is kept negative. If a filter rated
less than MERV-14 is utilized, the space shall be considered “Negative” with regards to the table and must comply
with all other requirements for negative spaces within the standard.
dd. See Section 7.4.1(c).
ee. Minimum MERV-14 filters shall be required for spaces where sterile equipment is packed into sterile packages.
MERV-8 filters may be used in place of MERV-14 in spaces where sterile products are stored in sealed packaging
but are not opened or otherwise handled outside of the sealed package.
ff. The facility governing body shall inform design engineers relating to room function or use (which function is
applicable) for Class 1, Class 2, or Class 3 imaging rooms.
gg. As an exception to the standard, alternative ventilation is allowed that provides a fan mounted in a mechanical
space outside the room that supplies air through a HEPA filter to the ceiling diffuser.
door air change rate listed in this standard shall be interpreted as the zone outdoor airflow (Voz) for purposes of this calculation.
7. Unless a higher ventilation rate is stipulated in Table 8-1 or elsewhere in this standard, wherever anesthetic gases are administered outside of an operating room,
procedure room, or Class 2 and Class 3 imaging rooms, ventilation shall be provided at a minimum rate of 2 outdoor ach and 6 total ach. (Informative Notes: [1]
Refer to NFPA 99 [2021] for WAGD piping and gas scavenging requirements. [2]
“Anesthetic gases” commonly refers to nitrous oxide and xenon but may also
include halogenated volatile anesthetic agents such as desflurane, sevoflurane, and
isoflurane.)
b. Air filtration for spaces shall comply with Section 6.4 and Table 8-1.
c. Supply air outlets for spaces shall comply with Table 6-2.
d. In AII rooms and operating and procedure rooms, heating with supply air or radiant
panels that meet the requirements of Section 6.5.3 shall be provided.
e. In a building that contains a mixture of spaces programmed for outpatient care as well
as spaces programmed for inpatient care, the outpatient care spaces shall be designed
in accordance with Tables 8-1 and 8-2, and the inpatient care spaces shall be designed
in accordance with Table 7-1.
8.2 General Outpatient Facility Requirements. All outpatient facility types other than
those indicated in Section 8.1 shall comply with this section and Table 8-2.
Unless otherwise noted in this section, all requirements for space ventilation of general
outpatient spaces are contained within this section and Table 8-2, and Sections 6, 7, 9, and
10 of this standard shall not apply. For requirements related to Sections 6 and 10, which
are not found in this section, refer to local and state building codes. Where no local or state
code is recognized, the requirements of ASHRAE Standard 62.1 1 shall apply.
(Informative Note: ASHRAE recognizes that ASHRAE standards are typically the
foundation of state and local building codes. However, state and local codes also represent
important regional interests and conditions. As such, state and local building codes shall
also be followed to the maximum extent practicable.)
28
ANSI/ASHRAE/ASHE Standard 170-2021
ANSI/ASHRAE/ASHE Standard 170-2021
29
Negative
NR
NR
Negative
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
Negative
Negative
NR
NR
NR
NR
NR
Negative
Urgent care treatment (FGI 2.5-3.2.2) (e)
Urgent care triage (FGI 2.5-3.2.3)
Urgent care observation (FGI 2.5-3.3)
General examination room (FGI 2.1-3.2.1)
Specialty IC exam room (FGI 2.5-3.2.3) (b)
Laboratory work room (FGI 2.1-4.1.2.1) (l)
Medication room (FGI 2.1-3.8.8.2)
Class 1 Imaging rooms (FGI 2.1-3.5) (g)
Psychiatric examination room (FGI 2.11-3.2.2)
Psychiatric consultation room (FGI 2.11-3.2.4)
Psychiatric group room (FGI 2.11-3.2.5)
Psychiatric seclusion room (FGI 2.11-3.2.7)
ECT procedure room (FGI 2.11-3.2.9.2)
Physical therapy individual room (FGI 2.12-3.2.2.1)
Physical therapy exercise area (FGI 2.12-3.2.3)
Hydrotherapy (FGI 2.12-3.2.4)
Physical therapeutic pool (FGI 2.12-3.2.4)
Speech therapy room (FGI 2.12-3.3.2)
Occupational therapy (FGI 2.12-3.3)
Prosthetics and orthotics room (FGI 2.12-3.3.1)
Dental treatment (FGI 2.14-3.1.1)
Other dental treatment areas (FGI 2.14-3.2)
Toilet room (FGI 2.1-3.10.2)
NR
Negative
Clean supply (FGI 2.1-3.8.11) (m) (n)
Soiled holding (FGI 2.1-3.8.12) (m) (o) (p)
Informative Note: NR = no requirement
Negative
Environmental services room (FGI 2.1-5.3.1)
SERVICE /SUPPORT SPACE
NR
NR
Urgent care exam (FGI 2.5-3.2.1) (e)
NR
Birthing room (FGI 2.4-2.2)
GENERAL DIAGNOSTIC AND TREATMENT
Function of Space (f)
Pressure
Relationship
to Adjacent
Areas (d)
6
2
2
NR
6
4
NR
NR
3
2
3
2
3
2
2
2
10
2
3
3
2
2
3
2
2
2
2
2
3
3
2
3
2
2
2
3
2
2
3
2
3
2
2
2
2
2
3
3
2
2
3
3
2
2
3
2
Min.
Min.
Outdoor Total
ach (q)
ach (q)
ach Design Option
Table 8-2 Design Parameters—General Outpatient Spaces (q)
Yes
NR
Yes
Yes
NR
NR
NR
NR
NR
Yes
Yes
NR (h)
NR (h)
NR
NR
NR
NR
NR
NR
NR
NR (h)
Yes
NR
NR
Yes
NR
NR
NR (h)
All Room Air
Exhausted
Directly to
Outdoors (j)
No
NR
No
No
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
Air
Recirculated
by Means of
Room Units
(a)
MERV- 8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-14
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
Max 60
Max 60
NR
Max 60
NR
NR
Max 60
NR
NR
Max 60
Min. Filter
Efficiencies Design
(c)
RH% (i)
NR
NR
NR
NR
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
72–80/22–27
72–80/22–27
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
72–78/22–26
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
70–75/21–24
3
1
3
3
1
1
2
1
1
3
3
2
2
1
2
1
1
1
1
1
2
3
1
2
3
2
2
2
Design
Air
Temperature Class
°F/°C (k)
(q)
5 (2.5) / 2
5 (2.5) / 2
—
—
5 (2.5) / 2
10 (5) / 3
10 (5) / 3
5 (2.5) / 2
5 (2.5) / 2
—
20 (10) / 2
20 (10) / 2
10 (5) / 3
7.5 (3.8) / 3
10 (5) / 3
5 (2.5) / 2
5 (2.5) / 2
5 (2.5) / 2
7.5 (3.8) / 2
5 (2.5) / 2
7.5 (3.8) / 2
10 (5) / 3
7.5 (3.8) / 3
5 (2.5) / 2
10 (5) / 3
7.5 (3.8) / 3
7.5 (3.8) / 3
10 (5) / 4
Rp
cfm/(L·s)/
person and
Min. Space
Population (q)
Rp-Ra
Air-Class Design Option
0.12 / (0.6)
0.12 / (0.6)
—
—
0.06 / (0.3)
0.18 / (0.9)
0.18 / (0.9)
0.06 / (0.3)
0.06 / (0.3)
0.48 / (2.4)
0.12 / (0.6)
0.18 / (0.9)
0.12 / (0.6)
0.12 / (0.6)
0.12 / (0.6)
0.06 / (0.3)
0.06 / (0.3)
0.06 / (0.3)
0.12 / (0.6)
0.18 / (0.9)
0.12 / (0.6)
0.18 / (0.9)
0.12 / (0.6)
0.12 / (0.6)
0.18 / (0.9)
0.18 / (0.9)
0.12 / (0.6)
0.18 / (0.9)
Ra
cfm/ft/(L·s/m)
(q)
Normative Notes for Table 8-2:
a. Except where indicated by a “No” in this column, recirculating room HVAC units (with heating or cooling coils)
are acceptable for providing that portion of the minimum total air changes per hour that is permitted by Section
8.2(a)(5). Because of the cleaning difficulty and potential for buildup of contamination, recirculating room units
shall not be used in areas marked “No.”
b. Examination rooms (identified as “specialty infection control [IC] exam rooms”) programmed for use by patients
with undiagnosed gastrointestinal symptoms, undiagnosed respiratory symptoms, or undiagnosed skin symptoms.
c. Table entries are the minimum filter efficiencies required for the space. Refer to Section 6.4 of this document for
further clarification of filtration requirements. The minimum efficiency reporting value (MERV) is based on the
method of testing described in ASHRAE Standard 52.2 (Informative Note: ASHRAE [2012] in Informative
Appendix E).
d. Pressure monitoring devices are not required for any spaces indicated in Table 8-2. Simple visual methods such as
ball-in-tube or flutterstrip are suggested should pressurization verification of air-flow direction be desired or
required by others.
e. Treatment rooms used for procedures with nitrous oxide shall contain provisions for exhausting anesthetic waste
gases, and the minimum total air changes shall be increased to 6. When this condition occurs the Rp-Ra air-class
design option cannot be used.
f. Informative Note: Parenthetic notations following a space name are paragraph references to the relevant FGI
Guidelines (FGI 2018a, 2018b, 2018c) in Informative Appendix E. These paragraph references are provided to the
user to aid in the application of design requirements.
g. Refer to Table 8-1 under the space type “Diagnostic imaging waiting” for space ventilation requirements in an
instance where a facility proposes an imaging waiting area and their ICRA determines that the imaging waiting
area requires special consideration to reduce the risk of airborne infection transmission.
h. In some areas with potential contamination and/or odor concerns, exhaust air shall be discharged to the outdoors
and not recirculated to other areas. This exhaust may be localized by switch or timer or otherwise under operational
control of the facility staff or patient.
i. The relative humidity (RH) ranges listed are the minimum and/or maximum allowable at any point within the
design temperature range required for that space.
j. Unless otherwise noted in (h) above, the exhaust rate shall meet or exceed minimum total air change requirement.
k. Systems shall be capable of maintaining the rooms within the range during normal operation. Lower or higher temperature shall be permitted when patients’ comfort and/or medical conditions require those conditions.
l. This room is intended for basic blood and urine specimen testing and short-term storage only. Outpatient facilities
that provide the following specialized service spaces/rooms should consult Table 7-1 for ventilation requirements:
laboratory work areas, including the specialty lab services such as bacteriology, biochemistry, cytology, glasswashing, histology, media transfer, microbiology, nuclear medicine, pathology, serology, and/or sterilizing.
m. Outpatient facilities that provide the following specialized service spaces/rooms should consult Table 8-1 for ventilation requirements: laundry, general, and soiled linen sorting and storage.
n. Refer to Table 8-1 under the space type “Clean workroom or clean supply” for space ventilation requirements if a
clean workroom space is provided.
o. Refer to Table 8-1 under the space type “Soiled workroom or soiled holding” for space ventilation requirements if
a soiled workroom space is provided.
p. This space is permitted to include hazardous material storage (general medical waste). If actual regulated waste
holding is anticipated, refer to Table 8-1 under the space type “Regulated waste holding” for ventilation requirements.
q. See Section 8.2(a)(6) and 8.2(a)(8).
The following requirements shall apply for space ventilation:
a. Spaces shall be ventilated according to Table 8-2.
1. Design of the ventilation system shall provide air movement that 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 shall not compromise the pressure balancing
relationships or the minimum air changes required by the table.
2. The ventilation rates in this table are intended to provide for comfort as well as for
asepsis and odor control in spaces of a health care facility that directly affect
patient care. Ventilation rates for clinical spaces not specified here shall be that of
functionally equivalent spaces in the table. If no functionally equivalent spaces
exist in the table, ventilation requirements shall be obtained from ASHRAE Standard 62.1 1. Where spaces with prescribed rates in both Standard 62.1 and Table 82 of this standard exist, the higher of the two air change rates shall be used.
30
ANSI/ASHRAE/ASHE Standard 170-2021
3. For design purposes, pressure relationships shall be achieved by the following methods:
i. Spaces that require a positive or negative pressure relationship shall maintain the
required pressure relationship during room occupied hours.
ii. For systems utilizing air changes per hour, the minimum number of total air changes
indicated shall be either supplied for positive pressure rooms or exhausted for negative pressure rooms. For spaces that require a positive or negative pressure relationship, the number of air changes can be reduced when the space is unoccupied,
provided that the required pressure relationship to adjoining spaces is maintained
while the space is unoccupied and that the minimum number of air changes indicated
is reestablished anytime the space becomes occupied. Controls intended to switch the
required pressure relationships between spaces from positive to negative, and vice
versa, shall not be permitted. Air change rates in excess of the minimum values are
expected in some cases in order to maintain room temperature and design relative
humidity conditions based on the space cooling or heating load.
4. All ventilation required by Table 8-2 shall meet the filtration requirements of Section
6.4 and Section 8.2.
5. For spaces where Table 8-2 permits air to be recirculated by room units, the portion of
the minimum total air changes per hour required for a space that is greater than the minimum outdoor air changes per hour required component may be provided by recirculating room HVAC units. Such recirculating room HVAC units shall
i. not receive nonfiltered, nonconditioned outdoor air;
ii. provide the manufacturer’s recommended filter (or MERV-8 as a minimum) for airflow passing over any surface that is designed to condense water. This filter shall be
located upstream of any such cold surface, so that all of the air passing over the cold
surface is filtered.
6. For air-handling systems utilizing the cfm/person and cfm/ft2 outdoor air ventilation
rates, system minimum outdoor air quantity shall be calculated by the Ventilation Rate
Procedure of ASHRAE Standard 62.1 1. The cfm/person rate shall be considered the Rp
value, and the cfm/ft2 rate shall be considered the Ra value in the calculation.
i. The minimum space population is provided as a required minimum in the “Rp” column of Table 8-2. The design zone population (Pz) shall equal the largest (peak)
number of people expected to occupy the room/space during typical use. When the
design zone population is less than the space population, use the minimum space
population.
ii. A zone minimum primary airflow (for multiple-zone recirculating systems) shall be
provided as follows: For each zone, the minimum primary airflow (Vpz-min) shall be
determined by the equation Vpz-min = Voz × 1.5.
7. For air-handling systems serving multiple spaces and utilizing the “Minimum Outdoor
ach” column, system minimum outdoor air quantity shall be calculated using one of the
following methods:
i. System minimum outdoor air quantity for an air-handling system shall be calculated
as the sum of the individual space requirements as defined by this standard.
ii. System minimum outdoor air quantity shall be calculated by the Ventilation Rate
Procedure (multiple zone formula) of ASHRAE Standard 62.1 1. The minimum outdoor air change rate listed in this standard shall be interpreted as the zone outdoor
airflow (Voz) for purposes of this calculation.
8. In lieu of calculating ventilation via air change rate (ach), an optional path allows calculating ventilation rate using provided values for cfm/person (Rp) and cfm/ft2 area (Ra)
and air class. This alternative design path option excludes compliance with the space
total air change rate (ach) requirement. This alternative design path option is only applicable to Table 8-2 spaces. (Informative Note: There is no correlation expected or
intended between the two design path options.)
9. A night setback or unoccupied mode (to maintain a temperature range of 55°F to 85°F
[13°C to 30°C] with a maximum of 65% design relative humidity) is permitted where
pressurization is not required and where facilities are closed and unoccupied for blocks
of time, such as nights and weekends.
ANSI/ASHRAE/ASHE Standard 170-2021
31
8.3 Additional Room-Specific Requirements
8.3.1 Airborne Infection Isolation (AII) Rooms. Refer to Section 7.2.1 of this standard.
8.3.2 Protective Environment (PE) Rooms. Refer to Section 7.2.2 of this standard.
8.4 Surgery Rooms
8.4.1 Operating Rooms (ORs), Operating/Surgical Cystoscopic Rooms, and Caesarean
Delivery Rooms. Refer to Section 7.4.1 of this standard.
8.4.2 Sterilization Rooms. Steam that escapes from a steam sterilizer shall be exhausted
using an exhaust hood or other suitable means. Ethylene oxide that escapes from a gas sterilizer shall be exhausted using an exhaust hood or other suitable means.
8.5 Support Spaces
8.5.1 Nonrefrigerated Body Holding Rooms. This space type is not listed in Tables 8-1 or
8-2; however, the following specific functional elements are relative to any facility with a body
holding room. A nonrefrigerated body holding room is applicable only to facilities that do not
perform autopsies on site and use the space for short periods while waiting for the body to be
transferred.Ventilation for nonrefrigerated body holding rooms shall meet the following
requirements:
a. All exhaust air from nonrefrigerated body holding rooms shall be discharged directly to the
outdoors without mixing with air from any other room or exhaust system.
8.5.2 Bronchoscopy
a. Differential pressure between bronchoscopy procedure and sputum induction rooms and any
adjacent spaces that have other functions shall be a minimum of –0.01 in. of water (–2.5 Pa).
b. Local exhaust shall be provided for sputum collection procedures.
8.5.3 Medical/Anesthesia Gas Storage Rooms. Ventilation for medical/anesthesia gas storage rooms shall comply with NFPA 99 13.
8.6 Behavioral and Mental Health Patient Areas. HVAC systems and related controls shall
be secured as called for in the patient safety risk assessment. All exposed equipment located
with these spaces shall have enclosures with rounded corners and tamper-resistant fasteners.
With the exception of HVAC room recirculating units, equipment shall be arranged such that
maintenance personnel are not required to enter patient care spaces for service, unless approved
by the AHJ when such arrangement is not possible. Seclusion, restraint, and observation rooms
intended for behavioral and mental health patients shall use fully recessed, vandal-resistant
grilles with diffuser blades designed for ligature-resistant and anticontraband capability.
8.7 Nuclear Medicine. Refer to Table 8-1 of this standard for both nuclear medicine treatment
spaces and nuclear medicine hot-lab spaces when radiopharmaceutical preparation is performed on site (not premixed) and radioactive materials (radionuclides) are mixed/distributed
from their protective containers within this room. If dose administration and on-site mixing
and preparation uses only low-level premixed radioactive materials, then a hot lab is not indicated and these nuclear medicine spaces will follow the general examination room space in
Table 8-2 of this standard for ventilation requirements.
9. SPACE VENTILATION—RESIDENT HEALTH, CARE, AND SUPPORT SPACES
The ventilation requirements of this standard are minimums that provide control of environmental comfort, asepsis, and odor in resident care areas. However, because they are minimum
requirements, and because of the diversity of the population and variations in susceptibility and
sensitivity, these requirements do not provide assured protection from discomfort, airborne
transmission of contagions, and odors.
9.1 General Requirements. The following general requirements shall apply for space ventilation:
a. Spaces shall be ventilated according to Table 9-1.
1. Design of the ventilation system shall provide air movement that 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 shall not compromise the pressure balancing relationships or the minimum air changes required by the table.
32
ANSI/ASHRAE/ASHE Standard 170-2021
ANSI/ASHRAE/ASHE Standard 170-2021
33
Positive
Negative
Negative
Negative
SUPPORT SPACE
Clean utility (FGI 2.3–4.2.5)
Environmental services room (FGI 2.3–4.9) (j)
Hazardous waste storage (FGI 2.3–4.8)
Soiled utility or soiled holding (FGI 2.3–4.2.6)
Informative Note: NR = No requirement
2
NR
NR
NR
Negative
Negative
2
NR
2
2
NR
NR
2
NR
2
NR
NR
NR
NR
NR
2
NR
2
NR
NR
2
NR
2
2
4
2
NR
NR
Positive
NR
NR
Negative
Negative
Negative
NR
NR
NR
NR
Negative
(e)
NR
NR
Negative
Negative
Negative
NR
Negative
NR
NR
NR
Negative
SERVICE
Clean linen storage (FGI 2.3–4.6)
Dietary storage (FGI 2.3–4.5)
Food preparation center (FGI 2.3–4.5.3.3) (e)
Hair salon (FGI 2.3–2.3.5 & 4.1–2.3.5)
Laundry, central and personal (FGI 2.3–4.2.7)
Linen and trash chute room
(FGI 2.3–4.6 & 2.3–4.9)
Medication room (FGI 2.3–4.2.2.2)
Soiled linen sorting and storage (FGI 2.3–4.6)
Warewashing (FGI 2.3–4.5.3.6)
ASSISTED LIVING FACILITIES
Resident living/activity/dining (FGI 4.1–2.3.3)
Resident room (FGI 4.1–2.2.2)
Resident corridor (FGI 2.4–2.2.2)
Toilet/bathing room (FGI 4.1–2.2.2.7)
HOSPICE FACILITIES
AII room (FGI 3.2–2.2.3.1) (c)
AII anteroom (FGI 3.2–2.2.3.1) (c)
Resident room (FGI 3.2–2.2.2)
Resident corridor (FGI 2.4–2.2.2)
Toilet/bathing room (FGI 3.2–2.2.2.6)
RESIDENTIAL CARE AND SUPPORT
NURSING HOMES
AII room (FGI 3.1–2.2.4.1) (b)
AII anteroom (FGI 3.1–2.2.4.1) (b)
Occupational therapy (FGI 3.1–3.3.3)
Physical therapy (FGI 3.1–3.3.2)
Resident living/activity/dining (FGI 3.1–2.3.3)
Resident room (FGI 3.1–2.2.2)
Resident corridor (FGI 2.4–2.2.2)
Toilet/bathing room (FGI 3.1–2.2.2.6)
RESIDENTIAL HEALTH
Function of Space (l)
Pressure
Relationship to
Minimum
Adjacent Areas (d) Outdoor ach
4
10
10
10
4
10
10
2
2
10
10
10
10
NR
NR
NR
NR
12
10
2
4
10
12
10
6
6
4
2
4
10
Minimum
Total ach
NR
Yes
Yes
Yes
NR
Yes
Yes
NR
NR
NR
Yes
Yes
Yes
NR
NR
NR
NR
Yes
Yes
NR
NR
Yes
Yes
Yes
NR
NR
NR
NR
NR
Yes
All Room Air
Exhausted
Directly to
Outdoors (f)
Table 9-1 Design Parameters for Residential Health, Care, and Support-Specific Spaces
NR
NR
No
No
NR
No
No
NR
No
No
NR
No
No
NR
NR
NR
NR
No
No
NR
NR
No
No
No
NR
NR
NR
NR
NR
No
No
No
No
No
Yes
No
Yes
No
No
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Air Recirculated
by Means of
Unoccupied
Room Units (a) Turndown
MERV-8 (k)
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-8
MERV-14
MERV-8
MERV-8
MERV-8
MERV-8
MERV-14
MERV-14
MERV-14
MERV-14
MERV-14
MERV-14
MERV-14
MERV-14
NR
NR
NR
NR
Max 60
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
Max 60
Max 60
Max 60
NR
NR
Max 60
Max 60
NR
NR
Max 60
Max 60
NR
NR
NR
NR
NR
NR
70–75/21–24
NR
NR
72–78/22–26
72–78/22–26
72–78/22–26
70–78/21–29
NR
NR
NR
70–78/21–29
NR
NR
70–75/21–24
NR
70–75/21–24
NR
70–75/21–24
70–78/21–29
70–78/21–29
70–78/21–29
70–78/21–29
70–78/21–29
70–78/21–29
70–78/21–29
70–78/21–29
Minimum
Design
Filter
Design Relative Temperature (h),
Efficiencies (i) Humidity (g), % °F/°C
Normative Notes for Table 9-1:
a. Except where indicated by a “No” in this column, recirculating room HVAC units (with heating or cooling coils) are
acceptable for providing that portion of the minimum total air changes per hour that is permitted by Section 9.1 (subparagraph [a][5]). Because of the cleaning difficulty and potential for buildup of contamination, recirculating room
units shall not be used in areas marked “No.” Recirculating devices with high-efficiency particulate air (HEPA) filters shall be permitted in existing facilities as interim, supplemental environmental controls to meet requirements for
the control of airborne infectious agents. The design of either portable or fixed systems should prevent stagnation
and short circuiting of airflow. The design of such systems shall also allow for easy access for scheduled preventative maintenance and cleaning.
b. The AII room described in this standard shall be used for isolating the airborne spread of infectious diseases, such as
measles, varicella, or tuberculosis. Supplemental recirculating devices using HEPA filters shall be permitted in the
AII room to increase the equivalent room air exchanges; however, the minimum outdoor air changes of Table 9-1 are
still required. When the AII room is not used for airborne infection isolation, the pressure relationship to adjacent
areas, when measured with the door closed, shall remain unchanged, and the minimum total air change rate shall be
6 ach.
c. Applicable for central air-handling systems only.
d. If pressure-monitoring device alarms are installed, allowances shall be made to prevent nuisance alarms. Short-term
excursions from required pressure relationships shall be allowed while doors are moving or temporarily open. Simple visual methods, such as smoke trail, ball-in-tube, or flutterstrip, shall be permitted for verification of airflow
direction.
e. Minimum total air changes per hour (ach) shall be that required to provide proper makeup air to kitchen exhaust systems as specified in ASHRAE Standard 154 14.In some cases, excess exfiltration or infiltration to or from exit corridors compromises the exit corridor restrictions of NFPA 90A 15, the pressure requirements of NFPA 96 16, or the
maximum defined in the table. During operation, a reduction to the number of air changes to any extent required for
odor control shall be permitted when the space is not in use.
f. In some areas with potential contamination and/or odor problems, exhaust air shall be discharged directly to the outdoors and not recirculated to other areas. Individual circumstances may require special consideration for air
exhausted to the outdoors. To satisfy exhaust needs, constant replacement air from the outdoors is necessary when
the system is in operation.
g. The relative humidity (RH) ranges listed are the minimum and/or maximum allowable at any point within the design
temperature range required for that space.
h. Systems shall be capable of maintaining the rooms within the range during normal operation. Lower or higher temperature shall be permitted when residents’ comfort and/or medical conditions require those conditions.
i. Table entries are the minimum filter efficiencies required for the space. Refer to Section 6.4 of this document for further clarification of filtration requirements. The minimum efficiency reporting value (MERV) is based on the method
of testing described in ASHRAE Standard 52.2 (Informative Note: ASHRAE [2012] in Informative Appendix E).
j. Environmental services room includes janitor’s and housekeeping closets.
k. Minimum MERV-14 filters shall be required for spaces where sterile equipment is packed into sterile packages.
Spaces where sterile products are stored but not packed shall not be required to have MERV-14 filters.
l. Informative Note: Parenthetic notations following a space name are paragraph references to the relevant FGI
Guidelines (FGI 2018a, 2018b, 2018c) in Informative Appendix E. These paragraph references are provided to the
user to aid in the application of design requirements.
2. The ventilation requirements in this table are intended to provide for comfort as
well as for asepsis and odor control in spaces of a residential health, care, or support facility that directly affect resident care. For spaces not specifically listed
here, ventilation requirements shall be that of functionally equivalent spaces in the
table. If no functionally equivalent spaces exist in the table, ventilation requirements shall be obtained from ASHRAE Standard 62.1 1 or ASHRAE Standard
62.2 17 in the absence of other codes or standards that govern those space ventilation
rate requirements. Where spaces with prescribed rates in both Standard 62.1 or
Standard 62.2 and Table 9-1 of this standard exist, the higher of the two air change
rates shall be used.
3. For design purposes, the minimum number of total air changes indicated shall be
either supplied for positive pressure rooms or exhausted for negative pressure
rooms. Spaces that are required in Table 9-1 to be at a negative pressure relationship and that are not required to be exhausted shall use the supply airflow rate to
compute the minimum total air changes per hour required. Except where indicated
by a “No” in the “Unoccupied Turndown” column, the number of air changes shall
34
ANSI/ASHRAE/ASHE Standard 170-2021
be permitted to be reduced, and temperature and design relative humidity altered, when
the space is unoccupied, provided that the required pressure relationship to adjoining
spaces is maintained while the space is unoccupied and that the minimum number of air
changes, temperature, and design relative humidity indicated are reestablished anytime
the space becomes occupied. Controls intended to switch the required pressure relationships between spaces from positive to negative, and vice versa, shall not be permitted.
Air change rates in excess of the minimum values are expected in some cases in order to
maintain room temperature and design relative humidity conditions based on the space
cooling or heating load.
4. The entire minimum outdoor air changes per hour required by Table 9-1 for the space
shall meet the filtration requirements of Section 6.4 and Table 9-1.
5. For spaces where Table 9-1 permits air to be recirculated by room units, the portion of
the minimum total air changes per hour required for a space that is greater than the minimum outdoor air changes per hour required component may be provided by recirculating room HVAC units. Such recirculating room HVAC units shall
i. not receive nonfiltered, nonconditioned outdoor air;
ii. serve only a single space; and
iii. provide, as a minimum, the manufacturer’s recommended filter for airflow passing
over any surface that is designed to condense water. This filter shall be located
upstream of any such cold surface, so that all of the air passing over the cold surface
is filtered.
6. For air-handling systems serving multiple spaces, system minimum outdoor air quantity
shall be calculated using one of the following methods:
i. System minimum outdoor air quantity for an air-handling system shall be calculated
as the sum of the individual space requirements as defined by this standard.
ii. System minimum outdoor air quantity shall be calculated by the Ventilation Rate
Procedure (multiple zone formula) of ASHRAE Standard 62.1 1. The minimum outdoor air change rate listed in this standard shall be interpreted as the zone outdoor
airflow (Voz) for purposes of this calculation.
b. Air filtration for spaces shall comply with Table 9-1.
c. Supply air outlets for spaces shall comply with Table 6-2.
d. In AII rooms, heating with supply air or radiant panels that meet the requirements of Section 6.5.3 shall be provided.
9.2 Additional Room-Specific Requirements
9.2.1 Airborne Infection Isolation (AII) Rooms. Ventilation for AII rooms shall meet the
following requirements whenever an infectious resident occupies the room:
a. Each AII room shall comply with requirements of Tables 6-2 and 9-1. AII rooms shall have
a permanently installed device and/or mechanism to constantly monitor the differential air
pressure between the room (when occupied by residents with a suspected airborne infectious disease) and the corridor, whether or not there is an anteroom. A local visual means
shall be provided to indicate whenever negative differential pressure is not maintained.
b. All air from the AII room shall be exhausted directly to the outdoors.
Exception to 9.2.1(b): AII rooms that are retrofitted from standard resident rooms from
which it is impractical to exhaust directly outdoors may be provided with recirculated
air from the room’s exhaust on the condition that the air first passes through a HEPA
filter.
c. All exhaust air from the AII rooms, associated anterooms, and associated toilet rooms shall
be discharged directly to the outdoors without mixing with exhaust air from any other nonAII room or exhaust system.
d. Exhaust air grilles or registers in the resident room shall be located directly above the resident bed, on the ceiling or on the wall near the head of the bed, unless it can be demonstrated that such a location is not practical.
e. The room envelope shall be sealed to provide a minimum differential pressure of 0.01 in. of
water (2.5 Pa) across the envelope.
f. Differential pressure between AII rooms and adjacent spaces that are not AII rooms shall be
a minimum of –0.01 in. of water (–2.5 Pa). Spaces such as the toilet room and the anteroom
ANSI/ASHRAE/ASHE Standard 170-2021
35
(if present) that are directly associated with the AII room and open directly into the AII
room are not required to be designed with a minimum pressure difference from the AII room
but are still required to maintain the pressure relationships to adjacent areas specified in
Table 9-1.
g. When an anteroom is provided, the pressure relationships shall be as follows: (1) the AII
room shall be at a negative pressure with respect to the anteroom, and (2) the anteroom
shall be at a negative pressure with respect to the corridor.
9.3 Behavioral and Mental Health Facilities
9.3.1 General. These spaces are intended for the care and treatment of inpatients who do not
require acute medical services.
9.3.2 Behavioral and Mental Health Patient Areas. HVAC systems and related controls
shall be secured as called for in the patient safety risk assessment. All exposed equipment
located with these spaces shall have enclosures with rounded corners and tamper-resistant fasteners. With the exception of HVAC room recirculating units, equipment shall be arranged
such that maintenance personnel are not required to enter patient-care spaces for service,
unless approved by the AHJ when such arrangement is not possible. Seclusion, restraint, and
observation rooms intended for behavioral and mental health patients shall use fully recessed,
vandal-resistant grilles with diffuser blades designed for ligature-resistant and anticontraband
capability.
9.4 Support Spaces
9.4.1 Medical/Anesthesia Gas Storage Rooms. Ventilation for medical/anesthesia gas storage rooms shall comply with NFPA 99 13.
9.4.2 Food preparation areas. Provide proper makeup air to kitchen exhaust systems as
specified in ANSI/ASHRAE Standard 154 14. Kitchens with Type I hoods shall be designed to
have a negative pressure with respect to adjacent areas.
Informative Note: In some cases, excess exfiltration or infiltration to or from exit corridors compromises the exit corridor restrictions of NFPA 90A 15 or the pressure requirements of
NFPA 96 16.
10. CONSTRUCTION AND SYSTEM START-UP
10.1 Construction Phase
10.1.1 Application. The requirements of this section apply to ventilation systems and the
spaces they serve in new buildings, and in additions to or alterations in existing buildings,
during the construction phase of the project.
10.1.2 Protection of Materials. When recommended by the manufacturer, building materials shall be protected from rain and other sources of moisture by appropriate in-transit and onsite procedures. Porous materials with visible microbial growth shall not be installed. Nonporous materials with visible microbial growth shall be decontaminated.
10.1.3 Duct Cleanliness. The duct system shall meet the following requirements for cleanliness:
a. The duct system shall be free of construction debris. New supply duct system installations
shall comply with level “C,” the Advanced Level of SMACNA Duct Cleanliness for New
Construction Guidelines 18.
b. The supply diffusers in operating rooms (ORs), delivery rooms (Caesarean), trauma rooms
(crisis or shock), wound intensive care rooms, protective environment (PE) rooms, and critical and intensive care rooms shall be opened and cleaned before the space is initially used
and at regular intervals thereafter.
c. The permanent HVAC systems shall not be operated unless protection from contamination
of the air distribution system is provided.
10.1.4 Protection of Occupied Areas
10.1.4.1 Application. The requirements of Section 10.1.4 apply when construction entails
sanding, cutting, grinding, or other activities that generate significant amounts of airborne particles or procedures that generate significant amounts of gaseous contaminants.
36
ANSI/ASHRAE/ASHE Standard 170-2021
10.1.4.2 Protective Measures. Measures shall be employed to reduce the migration of
construction-generated contaminates to occupied areas. When required, follow the ICRA
established procedures from Section 5.5 to minimize the disruption of facility operation and
the distribution of dust, odors, and particulates.
10.1.4.3 HVAC During Construction
a. Provide conditions to aid in preventing microbial growth on materials that are or will be
installed in the new or remodeled facility or addition.
b. As determined from Section 5.6, if the permanent HVAC equipment is to be used during
construction for temperature and/or humidity control, then prior to its use take the following minimum steps:
1. Supply 100% outdoor air—no return air; blank off return duct openings with solid
material.
2. Provide a method for pressure relief, such as open window(s) or door(s).
3. Provide final level of filtration in air-handling units (AHUs).
4. Cover supply duct openings when air-handler(s) are OFF.
5. Provide prefilters over outdoor air intakes as needed during site construction activities.
6. Clean air-handling components prior to occupancy.
7. Operate AHU(s) only if safety devices and sequences are in place and operational.
c. Prior to starting and operating any ventilation systems from the time the testing, adjusting,
and balancing work is taking place to the completion of the project, isolate expected construction activities that produce dust and debris from the ventilation systems.
10.2 System Start-Up
10.2.1 Application. This section applies to HVAC equipment and systems designed and
installed to meet the requirements of this standard.
10.2.2 Testing, Adjusting, and Balancing (TAB). HVAC systems shall be balanced in
accordance with one of the following national standards: ASHRAE Standard 111 19, AABC,
NEBB, or TABB for airflows, water flows, and relative room air pressurization.
10.2.3 Testing of Drain Pans. To minimize conditions of water stagnation that may result in
microbial growth, inspect drain pans to verify proper drainage under operating conditions.
10.2.4 Manufactured Equipment Start-Up. For all manufactured HVAC equipment components, follow manufacturer’s start-up recommendations and requirements. All equipment
and air distribution systems shall be clean of dirt and debris.
10.2.5 Documentation of New or Remodeled HVAC Systems. Owners shall retain an
acceptance testing report for their files. In addition, the design shall include requirements for
operations and maintenance (O&M) staff training that is sufficient for the staff to keep all
HVAC equipment in a condition that will maintain the original design intent for ventilation.
Training of operating staff shall include an explanation of the design intent. The training materials shall include, at a minimum, the following:
a. O&M procedures
b. Temperature and pressure control operation in all modes
c. Acceptable tolerances for system temperatures and pressures
d. Procedures for operations under emergency power or other abnormal conditions that have
been considered in the facility design
11. NORMATIVE REFERENCES
1.
2.
3.
4.
ASHRAE. 2019. ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air
Quality. Atlanta: ASHRAE.
SMACNA. 2005. HVAC Duct Construction Standards, Metal and Flexible, Third Edition.
Chantilly, VA: Sheet Metal and Air Conditioning Contractors’ National Association.
AIHA/ASSE. 2012. ANSI/AIHA/ASSE Z9.5, American National Standard for Laboratory Ventilation. Park Ridge, IL: American Society of Safety Engineers.
ASHRAE. 2017. ANSI/ASHRAE Standard 52.2, Method of Testing General Ventilation
Air-Cleaning Devices for Removal Efficiency by Particle Size. Atlanta: ASHRAE.
ANSI/ASHRAE/ASHE Standard 170-2021
37
5.
GPO. 2013. Code of Federal Regulations, Title 21, Part 173, Section 310, Boiler Water
Additives. Washington, DC: U.S. Government Publishing Office. Available at http://
https://www.gpo.gov/fdsys/granule/CFR-2011-title21-vol3/CFR-2011-title21-vol3sec173-310.
6. Chen, Q., and L. Glickman. 2003. System Performance Evaluation and Design Guidelines
for Displacement Ventilation. Atlanta: ASHRAE.
7. USP. 2014. National Formulary USP-795, Pharmaceutical Compounding—Nonsterile
Preparations. Rockville, MD: U.S. Pharmacopeial Convention.
8. USP. 2019. National Formulary USP-797, Pharmaceutical Compounding—Sterile Preparations. Rockville, MD: U.S. Pharmacopeial Convention.
9. USP. 2017. National Formulary USP-800, Hazardous Drugs—Handling in Healthcare
Settings. Rockville, MD: U.S. Pharmacopeial Convention.
10. ASHRAE. 2019. ASHRAE Handbook—HVAC Applications. Atlanta: ASHRAE.
11. NIOSH. n.d. Criteria Documents. Atlanta: National Institute for Occupational Safety and
Health. Available at http://www.cdc.gov/niosh/pubs/criteria_date_desc_nopubnumbers.html.
12. AAMI. 2017. ANSI/AAMI Standard ST79, Comprehensive guide to steam sterilization
and sterility assurance in health care facilities. Arlington, VA: Association for the
Advancement of Medical Instrumentation.
13. NFPA. 2018. NFPA 99, Health Care Facilities Code. Quincy, Massachusetts: National
Fire Protection Association.
14. ASHRAE. 2016. ANSI/ASHRAE Standard 154, Ventilation for Commercial Cooking
Operations. Atlanta: ASHRAE.
15. NFPA. 2019. NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating
Systems. Quincy, MA: National Fire Protection Association.
16. NFPA. 2017. NFPA 96, Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations. Quincy, MA: National Fire Protection Association.
17. ASHRAE. 2016. ANSI/ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air
Quality in Residential Buildings. Atlanta: ASHRAE.
18. SMACNA. 2000. Duct Cleanliness for New Construction Guidelines. Chantilly, VA: Sheet
Metal and Air Conditioning Contractors’ National Association. Available at https://
www.smacna.org/technical/browse/papers-and-guidelines/technical-paper/2000/05/27/
duct-cleanliness-for-new-construction-guidelines.
19. ASHRAE. 2017. ANSI/ASHRAE ASHRAE Standard 111-2008 (RA 2017), Testing,
Adjusting, and Balancing of Building HVAC Systems. Atlanta: ASHRAE.
38
ANSI/ASHRAE/ASHE Standard 170-2021
(This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed
according to the ANSI requirements for a standard and may contain material that has
not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)
INFORMATIVE APPENDIX A
OPERATIONS AND MAINTENANCE (O&M) PROCEDURES
A1. O&M IN HEALTH CARE FACILITIES
The following operations and maintenance (O&M) procedures are recommended for health
care facilities.
A1.1 Operating Rooms (ORs)
a. Each OR should be tested for positive pressure semiannually or on an effective preventative
maintenance schedule.
b. Operating and Caesarean delivery room ventilation systems shall operate at all times,
except during maintenance and during conditions requiring shutdown by the building’s fire
alarm system.
A1.2 Protective Environment (PE) Rooms. PE rooms should remain under positive pressure
with respect to all adjoining rooms whenever an immunocompromised patient is present. PE
rooms should be tested for positive pressure daily when an immunocompromised patient is
present.
A1.3 Airborne Infection Isolation (AII) Rooms. AII rooms should remain under negative
pressure, relative to all adjoining rooms, whenever an infectious patient is present. They should
be tested for negative pressure daily whenever an infectious patient is present.
A1.4 Filters. Filters and filter frames should be visually inspected for pressure drop and for
bypass monthly. All filters and air cleaning devices shall be replaced or maintained per manufacturer recommendations.
A1.5 Unoccupied Turndown. When unoccupied turndown is implemented for a space, control and operate the turndown mode such that a relative humidity of 60% is not exceeded in the
space.
A2. SPECIAL MAINTENANCE FOR HVAC UNITS
The following special maintenance procedures are recommended for health care facilities.
A2.1 Fan-Coil Unit and Heat Pumps. The fan-coil unit and heat-pump filters serving patient
rooms should be inspected for pressure drop monthly, or on an effective preventative maintenance cycle, and should be replaced when that pressure drop causes a reduction in airflow. Fancoil unit and heat-pump drain pans under cooling coils should be cleaned monthly or on an
effective preventative maintenance cycle.
A2.2 Fin-Tube Radiation Units, Induction Units, and Convection Units. Fin-tube radiation
units, induction units, and convection units serving patient rooms should be cleaned quarterly
or on an effective preventative maintenance cycle.
A2.3 Fan-Powered Terminal Units. Fan-powered terminal-unit filters serving patient rooms
should be inspected for pressure drop monthly, or on an effective preventative maintenance
cycle, and should be replaced when the pressure drop causes a reduction in airflow.
A3. AIR INTAKE OPENING FOR AREAWAY
Figure A-1 illustrates the provisions of Section 6.3.1.4 for air intake openings for areaways.
ANSI/ASHRAE/ASHE Standard 170-2021
39
Figure A-1 Provisions for areaways.
40
ANSI/ASHRAE/ASHE Standard 170-2021
(This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed
according to the ANSI requirements for a standard and may contain material that has
not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)
INFORMATIVE APPENDIX B
THERMAL COMFORT
a. Section 2.7 was added to the scope of Standard 170 to better communicate that compliance
with Standard 170 does not ensure compliance with ASHRAE Standard 55 (2017).
b. ASHRAE Standard 55 specifies the combination of environmental factors (temperature,
thermal radiation, humidity, air speed) and personal factors (activity level and clothing) that
will produce thermal conditions acceptable to the majority of healthy occupants. However,
there are scenarios and spaces within health care facilities where Standard 55 does not
apply or where deviations from Standard 55 are required.
c. Standard 170 provides HVAC design temperature and humidity ranges that, while potentially affecting occupant comfort, are also provided in support of therapeutic patient outcomes, aseptic practices, and worker protection.
ANSI/ASHRAE/ASHE Standard 170-2021
41
(This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed
according to the ANSI requirements for a standard and may contain material that has
not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)
INFORMATIVE APPENDIX C
AIR CLASSIFICATIONS
ASHRAE Standard 62.1 (2019) categorizes spaces into air classifications and prevents the recirculation and transfer of air under many conditions from spaces with higher air classifications to
spaces with lower air classifications based on ASHRAE Standard 62.1, Section 5.18. This
appendix includes guidelines on how to apply air classifications to ASHRAE/ASHE Standard
170 spaces.
a. Air classifications should be applied as indicated below and in accordance with ASHRAE
Standard 62.1, Section 5.18.
b. Recirculation allowances by room units shall be in accordance with the room recirculation
requirements of Tables 7-1, 8-1, 8-2, and 9-1 and Standard 62.1, Section 5.18. (Note: This
should not be construed to prevent room recirculation of air within the same space when
permitted by Standard 170 but prevented by Standard 62.1 air classifications.)
c. Energy recovery devices serving Standard 170 spaces should meet the requirements of
Standard 170, Section 6.8.
d. Spaces in Tables 7-1, 8-1, 8-2, and 9-1 requiring 100% exhaust air should be Class 3 air.
Exceptions to (d):
1. Spaces listed in Section 6.3.2.1 should be Class 4 air.
2. For spaces with Class 3 and 4 air, room recirculation should be as permitted by
HEPA filtration when indicated in Tables 7-1, 8-1, 8-2, and 9-1 and associated notes.
e. Spaces requiring negative pressure but not 100% exhaust air should be Class 2 air. The following list of spaces should also be considered Class 2 air:
1. Resident gathering/activity/dining (mild odor contaminants)
2. Resident room in skilled nursing facilities (mild odor contaminants)
3. Resident unit corridor in skilled nursing facilities (mild odor contaminants)
4. Laboratory work area, media transfer (mild odor contaminants)
5. Special examination room (biological concerns)
6. Pharmacy (mild odor contaminants)
f. All other spaces should be Class 1 air.
g. Variability of contaminants by space use is expected. When additional contaminants will
occur in a space than may typically be expected, designers should designate a higher air
classification for that space if appropriate. Designers should not designate a lower air classification for a space than is indicated.
42
ANSI/ASHRAE/ASHE Standard 170-2021
(This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed
according to the ANSI requirements for a standard and may contain material that has
not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)
INFORMATIVE APPENDIX D
RECOMMENDED FILTER EFFICIENCIES BY SPACE TYPE
Spaces in Tables 7-1, 8-1, 8-2, and 9-1 of this standard have filter efficiencies assigned based on
Table D-1. This table is provided for information to allow users to understand the intent of the
filter assignments and make engineering judgments on spaces not specifically named in the
standard.
Table D-1 Recommended Filter Efficiencies by Space Type
Filter Efficiency
Recommendations a,b
Level
Space Category
I
• Primarily exhausted space (e.g., restrooms, janitor’s rooms)
• Any human-occupied space
• Any room, inpatient or outpatient, where a patient stays less than 6 hours including waiting
rooms
• Laboratories
• Resident rooms in assisted living or hospice
• Storage of packaged sterile material, clean linen, or pharmaceuticals c
• Treatment rooms, endoscopy procedure room
• Dirty side of decontamination process
II
•
•
•
•
•
•
III
• Operating room h
MERV16 f
IV
• Operating room designated for orthopedic, transplants, neurosurgery, or dedicated burn unit
procedures
• Protective environments, including burn units
HEPA
Inpatient spaces, including medical-surgical, airborne isolation d
Special exam room for suspect airborne cases, emergency department exam rooms e
Resident room in a skilled nursing area
Workroom for packing of sterile materials
CT or MRI procedure, interventional radiology (including biopsy), or bronchoscopy
ER procedure or trauma room
MERV 8 (equivalent to
ASHRAE 62.1 or Standard 62.2)
MERV14 f,g
Notes:
a. Where listed, MERV rating is assumed to be nondegrading.
b. Transfer air due to differences in pressure between spaces may be unfiltered.
c. Pharmacy compounding spaces are not covered in this table. Follow USP 795, USP 797, or USP 800, as applicable (see Section 11 references).
d. Does not include recirculated air. Air recirculated in an AII room requires HEPA filters.
e. Air from spaces where suspected airborne cases may be treated or examined should be filtered at level II prior to recirculation to other spaces. If exhausted, supply air filtration
may be level I.
f. Minimum MERV rating of the highest efficiency filter in the airstream.
g. Filter efficiency if supply air is used; not intended to exclude natural ventilation if otherwise allowed.
h. An optional risk assessment, conducted with the user group, may indicate a need to increase from Level III to Level IV.
ANSI/ASHRAE/ASHE Standard 170-2021
43
(This appendix is not part of this standard. It is merely informative and does not contain
requirements necessary for conformance to the standard. It has not been processed
according to the ANSI requirements for a standard and may contain material that has
not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)
INFORMATIVE APPENDIX E
INFORMATIVE REFERENCES AND BIBLIOGRAPHY
ACGIH. 2001. Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices, 7th Ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
ACS. 2000. Guidelines for Optimal Ambulatory Surgical Care and Office-based Surgery, Third
edition. Chicago, IL: American College of Surgeons.
ASHRAE. 2013. HVAC Design Manual for Hospitals and Clinics, 2nd Edition. Atlanta:
ASHRAE.
ASHRAE. 2016a. ANSI/ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air
Quality in Residential Buildings. Atlanta: ASHRAE.
ASHRAE. 2016b. ASHRAE Position Document on Limiting Indoor Mold and Dampness in
Buildings. Atlanta: ASHRAE.
ASHRAE. 2017a. ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for
Human Occupancy. Atlanta: ASHRAE.
ASHRAE. 2017b. ASHRAE Handbook—Fundamentals. Atlanta: ASHRAE.
ASHRAE. 2018. ASHRAE Standard 188, Legionellosis: Risk Management for Building Water
Systems. Atlanta: ASHRAE.
ASHRAE. 2019. ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality. Atlanta: ASHRAE.
ASHRAE 2020. ASHRAE Guideline 12, Managing the Risk of Legionellosis Associated with
Building Water Systems. Atlanta: ASHRAE.
ASTM. 2011. ASTM D1193-06 (2011), Standard Specification for Reagent Water. West Conshohocken, PA: American Society for Testing and Materials.
Bartholomew, P. 2015. Energy-efficient approach for operating rooms. ASHRAE Journal
(April 2015):30–41.
BHFC. 2019. Behavioral Health Design Guide (Design Guide 9.0). Behavioral Health Facility
Consulting, LLC.
CDC. 2003. Guidelines for Environmental infection control in health-care facilities. Morbidity
and Mortality Weekly Report (MMWR) 52(RR10). Atlanta, GA: U.S. Department of
Health and Human Services, Centers for Disease Control and Prevention.
CDC. 2005. Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in
Health-Care Facilities. Atlanta, GA: U.S. Department of Health and Human Services,
Centers for Disease Control and Prevention.
Coogan, J.J. 1996. Effects of surrounding spaces on rooms pressurized by differential flow
control. ASHRAE Transactions 102(1).
CSA Group. 2015. CAN/CSA-Z317.2-15, Special Requirements for Heating, Ventilation, and
Air Conditioning Systems in Health Care Facilities, Fourth Edition. Toronto: CSA
Group.
FGI. 2018a. Guidelines for Design and Construction of Hospitals. St. Louis, MO: Facility
Guidelines Institute, American Society for Healthcare Engineering.
FGI. 2018b. Guidelines for Design and Construction of Outpatient Facilities. St Louis, MO:
Facility Guidelines Institute.
FGI. 2018c. Guidelines for Design and Construction of Residential Health, Care, and Support
Facilities. St Louis, MO: Facility Guidelines Institute.
Hayden, C.S., II; O.E. Johnston; R.T. Hughes; and P.A. Jensen. 1998. Air volume migration
from negative pressure isolation rooms during entry/exit. Applied Occupational and
Environmental Hygiene 13(7):518–27.
Hermans, RD. 2000. Health care facility design manual-room design. ASHRAE Transactions
106(2).
IEST. 2016. IEST PR-CC001.6, HEPA and ULPA Filters. Arlington Heights, IL: Institute of
Environmental Sciences and Technology.
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ANSI/ASHRAE/ASHE Standard 170-2021
Khankari, K. 2016. Patient room HVAC. ASHRAE Journal (June 2016):16–27.
Lewis, J.R. 1987. Operating room air distribution effectiveness. ASHRAE Transactions
93(2):1191–98.
Love, C. 2011. Operating Room HVAC Setback Strategies. ASHE Monograph. American
Society for Healthcare Engineering, Chicago, IL.
Memarzadeh, F. 2013. Literature review: Room Ventilation and Airborne Disease Transmission. Nomograph, American Society for Healthcare Engineering, Chicago, IL.
Memarzadeh, F., and A. Manning. 2002. Comparison of operating room ventilation systems in
the protection of the surgical site. ASHRAE Transactions 108(2).
Memarzadeh, F. and Z. Jiang. 2004. Effects of Operating Room Geometry and Ventilation System Parameter Variations on the Protection of the Surgical Site. IAQ 2004: Critical
Operations: Supporting the Healing Environment through IAQ Performance Standards.
NFPA. 2021. NFPA 99, Health Care Facilities Code. Quincy, MA: National Fire Protection
Association.
Ninomura, P., and J. Bartley. 2001. New ventilation guidelines for health-care facilities.
ASHRAE Journal, June 2001, Atlanta, GA.
Ninomura, P., C. Rousseau, and T. Ninomura. 2014. Current trends for health-care ventilation.
ASHRAE Journal (April 2014):32–43.
Ninomura, P., J. Bartley, and C. Rousseau. 2011. Health care standard update. ASHRAE Journal (March 2011):56–60.
OSHA. 29 CFR Part 1910.1047, Occupational Exposure to Ethylene Oxide. U.S. Department
of Labor, Occupational Safety and Health Administration, Washington, D.C.
SMACNA. 2000. Duct Cleanliness for New Construction Guidelines. Chantilly, VA: Sheet
Metal And Air Conditioning Contractors’ National Association, Inc.
ANSI/ASHRAE/ASHE Standard 170-2021
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ANSI/ASHRAE/ASHE Standard 170-2021
Approval Dates
• ASHRAE Std. Comm.
• ASHRAE BoD
• ASHE
• ANSI
7.5; 8.5; 9.5, Tables 7.1, 8.1, 9.1;
Informative Appendix D
• February 5, 2020
Addendum b removes several spaces from Tables 7.1, 8.1, and 9.1 based on those spaces being adequately
addressed in other standards. The addendum also modifies the minimum total air change requirements for several • February 5, 2020
• December 19, 2019
spaces based on the results of CO-RP 3.
• March 2, 2020
The change to filter requirements shifts the focus to a space-by-space-based approach, offering flexibility for users
of the standard to apply the filtration selections that most rationally meets their goals for first, operational and
energy costs. Filtration requirements were increased in some spaces and reduced in others, with the net effect of
maintaining safe environments for occupants.
a. The name and number of spaces in Table 7.1 are modified by Addendum p, which includes a similar format of
space-by-space filter assignments. The “Function of space” names in Table 7.1 have been updated and reorganized to be consistent with addendum p revisions.
b. The filter assignments here supersede or replace those shown in Addendum p.
c. Some line items have been removed from Table 7.1 due to addenda b and p.
d. Table 7.1, 8.1, and 9.1 names have been updated to match addendum n and p revisions.
e. Addendum n and p had removed previous material that is no longer shown in this addendum or sections have
different numbering due to those changes.
Furthermore, the presentation of this addendum has been updated from earlier public review releases for ease of
the users of the standard. Some of the reflected changes include:
6.4; 6.7.1; 6.8.1; 6.9; 7.1; Table 7.1;
Addendum a clarifies filtration requirements on a space-by-space basis. The filtration levels designated, and their • July 31, 2020
• August 10, 2020
7.2.2; 7.4.1; 8.1; Table 8.1; 8.3.1; Table rational basis, are included in Informative Appendix C, Table C-1. In brief, this addendum
• July 28, 2020
9.1; 11, A1; Informative Appendix B;
a. revises requirements for filters in the body of the standard, removes Table 6.4 and adds minimum filtration effi• September 1, 2020
new Informative Appendix C
ciencies by space in Table 7.1, 8.1, 9.1 and
b. adds Informative Appendix C, “Recommended Filter Efficiencies by Space Type.”
Description of Changes*
* These descriptions may not be complete and are provided for information only.
b
a
Addendum Sections Affected
Table F-1 ANSI/ASHRAE/ASHE Addenda to ANSI/ASHRAE/ASHE Standard 170-2017
ANSI/ASHRAE/ASHE Standard 170-2021 incorporates ANSI/ASHRAE/ASHE Standard 170-2017 and Addenda a, b, c, d, e, g, h, i, j, k, l,
m, n, p, q, r, and s to ANSI/ASHRAE/ASHE Standard 170-2017. Table E-1 lists each addendum and describes the way in which the standard is affected by the change. It also lists the ASHRAE, ASHE, and ANSI approval dates for each addendum.
Note: Tables 6.7.2, 7.1, 8.1, and 9.1 have been editorially renumbered as Tables 6-1, 7-1, 8-1, and 9-1, respectively. Additions and deletions of other tables are as indicated in the table below.
INFORMATIVE APPENDIX F
ADDENDA DESCRIPTION INFORMATION
(This appendix is not part of this standard. It is merely informative and does not contain requirements necessary for conformance to
the standard. It has not been processed according to the ANSI requirements for a standard and may contain material that has not
been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to
appeal at ASHRAE or ANSI.)
ANSI/ASHRAE/ASHE Standard 170-2021
47
6.3; added Table 6.3.1.1; added 6.7.6;
added 6.7.7; 6.9
5; 10
3; 7.1; 8.1; 9.1; 11
Informative Appendix B
6.6
d
e
g
h
i
Approval Dates
• ASHRAE Std. Comm.
• ASHRAE BoD
• ASHE
• ANSI
Addendum i changes Section 6.6 to clarify requirements for water in humidification systems.
Addendum h provides guidance to users of Standard 170 for considerations related to thermal comfort, with
acknowledgment and limitations of the role of ASHRAE Standard 55 requirements and how to incorporate
thermal comfort requirements into their design of Standard 170 spaces.
Addendum g creates a more harmonious reference to ventilation requirements for those spaces located within a
health care facility that are not explicitly specified within the three design parameter tables of the standard (Tables
7.1, 8.1, and 9.1). The new phrasing acknowledges that other space ventilation rate requirements likely exist in
other codes or standards for those spaces not included in the design parameter tables and that these spaces may
also be physically located within health care facilities. Addendum g also adds definitions of “patient” and
“resident” that are aligned with the FGI Guidelines and that provide additional clarity and assists users in avoiding
misinterpretation in application related to animal care.
These changes come from a critical review of Sections 5 and 10. Addendum e improves the flow of the standard
by moving the planning requirements from Section 10 into Section 5, “Planning.” The addendum also harmonizes
revised Section 10, “Construction and System Start-Up,” requirements with those in ASHRAE Standard 62.1.
SSPC 170 feels the changes represent minimum current design practices and should not present additional
economic burden to health care facility construction.
• Air intake separation distance table adapted for 170 requirements.
• Outdoor air verification requirements while operating.
• Measures to prevent vehicle combustion in parking garages from entering the building.
• Air balancing requirements.
Addendum d adds requirements and language similar to those required in Section 5 (Systems and Equipment) of
ASHRAE Standard 62.1. Requirements include:
February 5, 2020
February 5, 2020
December 19, 2019
March 2, 2020
April 1, 2020 (ASHRAE)
March 31, 2020 (ASHE)
APRIL 1, 2020 (ANSI)
December 20, 2019
(ASHRAE)
December 19, 2019
(ASHE)
December 20, 2019 (ANSI)
November 4, 2020
November 18, 2020
September 30, 2020
December 16, 2020
November 4, 2020
November 18, 2020
September 30, 2020
December 16, 2020
Addendum c provides guidance to users of Standard 170 on how to incorporate air classifications into their design • February 5, 2020
• February 5, 2020
of Standard 170 spaces if they are required to use them in conjunction with ASHRAE Standard 62.1.
• December 19, 2019
• March 2, 2020
Description of Changes*
* These descriptions may not be complete and are provided for information only.
Informative Appendix C
c
Addendum Sections Affected
Table F-1 ANSI/ASHRAE/ASHE Addenda to ANSI/ASHRAE/ASHE Standard 170-2017
48
ANSI/ASHRAE/ASHE Standard 170-2021
November 4, 2020
November 18, 2020
November 2, 2020
December 16, 2020
Approval Dates
• ASHRAE Std. Comm.
• ASHRAE BoD
• ASHE
• ANSI
Addendum L continues the process of reorganizing the standard into three components—Hospital, Outpatient, and
Residential Health Care and Support—in alignment with the FGI Guidelines’ transition to three separate
standards. Addendum L follows the continuing maintenance
process in further coordination with FGI and SSPC 170 to create in a coordinated document for use by all
stakeholders in the health care community. This addendum modifies Sections 3, 7, 8 and 9 and incorporate
changes previously made by Addenda a and p to Standard 170-2017 as follows:
a. Adds Addendum a updated filtration requirements to revised Table 7.1.
b. Adds Addendum p updated unoccupied turndown requirements to revised Table 7.1.
c. Revises the space name definitions and process definitions, table organization, and subheadings to better correlate with the 2018 FGI Guidelines for Design and Construction of Hospitals, including the addition of paragraph numbers after each space name. These revised 2018 FGI paragraph numbers have been coordinated with
FGI committee members and will be presented in italicized text to keep them as informative language
November 4, 2020
November 18, 2020
September 30, 2020
February 26, 2021
Addendum k accomplishes different objectives related to Table 9.1. Note that Table 9.1 entries were originally
July 31, 2020 (ASHRAE)
separated from Table 7.1 by Addendum n. Addendum k
July 28, 2020 (ASHE)
a. includes Table 9.1 requirements for unoccupied turndown of the spaces with input gathered from the First Public July 31, 2020 (ANSI)
Review of 2013 Addendum i and 2017 Addendum p;
b. reorganizes several existing Table 9.1 space entries into revised subheadings to better correlate with FGI;
c. clarifies and corrects table footnote sequencing that was erroneously included in Addendum n;
d. revises design temperature ranges and design relative humidity for several spaces; and
e. revises other table entries as noted.
* These descriptions may not be complete and are provided for information only.
3; 7.1; 7.4.1; deleted 7.4.3; 8.1; Table
8.1 notes; deleted 8.4.3; deleted 9.4.3;
Table 7.1;
9; Table 9.1
k
l
Addendum j continues the process of reorganizing the standard into three components—Hospital, Outpatient, and
Residential Health Care and Support in alignment with the FGI Guidelines’ transition to three separate standards.
The intent is not to create additional requirements for outpatient or residential facilities but to separate these from
hospital requirements and thus eliminate confusion over which requirements apply to which occupancies. The
result will be clarification of a lower level of requirements for outpatient and residential health facilities by
separating these from the higher requirement of inpatient facilities. Proposed Addendum j follows the continuing
maintenance process in further coordination with FGI staff and 170 staff to result in a coordinated document for
use by all stakeholders in the Healthcare Community. This addendum is the entire Chapter 8 and incorporates
Addendum ‘n’. Generally, the changes are as follows:
3; 8; Table 8.1; Table 8.2
j
a. Incorporate Addendum ‘a’ updated filtration requirements.
b. Revise the space name terminology, table organization, and subheadings to better correlate with the 2018 FGI
Guidelines for Design and Construction of Hospitals and Outpatient Facilities, including the addition of paragraph numbers after each space name. These revised 2018 FGI paragraph numbers have been coordinated with
FGI committee members and will be presented in italicized text to keep them as informative language.
Description of Changes*
Addendum Sections Affected
Table F-1 ANSI/ASHRAE/ASHE Addenda to ANSI/ASHRAE/ASHE Standard 170-2017
ANSI/ASHRAE/ASHE Standard 170-2021
49
Description of Changes*
Approval Dates
• ASHRAE Std. Comm.
• ASHRAE BoD
• ASHE
• ANSI
5; 6.4;
Table 6.4; 7.1;
Table 7.1; Informative Appendix A
1; 2
p
q
January 20, 2018
January 24, 2018
November 28, 2017
March 3, 2020
October 16, 2019
November 15, 2019
a. Adds “resident” to differentiate from “patient” in residential health applications (Section 2.1).
b. Clarifies that Standard 170 addresses more than outdoor air quantities to better differentiate from Standard 62.1 September 13, 2019
December 12, 2019
(Section 2.6)
c. Clarifies that Standard 170 does not establish “comprehensive thermal comfort design requirements.” Those
requirements are addressed in Standard 55 (Section 2.7).
d. The text of the standard will be coordinated with this revised scope in a future addendum, once the revised scope
is approved.
Addendum q makes changes to the scope of the standard. The following changes are made:
February 5, 2020
February 5, 2020
a. A column is created indicating spaces where unoccupied turndown is acceptable.
b. Table 6.4 is incorporated into Table 7.1 to remove confusion so that filter requirements will be uniformly December 19, 2019
March 2, 2020
applied.
c. Space names are aligned with names appearing in FGI 2014 and indicating the appropriate sections in FGI 2014
where that space is referenced. Numerous spaces have been relocated within the table with no changes to their
previous requirements, For these spaces previous locations are shown in strikethrough while the new locations
are shown in underline.
Addendum p incorporates updates to Table 7.1.
Addendum n continues the process of reorganizing the standard into three components—Hospital, Outpatient, and
Residential Health, Care, and Support—in alignment with the FGI Guidelines’ transition to three separate
standards. The intent is not to create additional requirements for outpatient or residential facilities but to separate
these from hospital requirements and thus eliminate confusion over which requirements apply to which
occupancies. The end result will be clarification of a lower level of requirements for outpatient and residential
health facilities by separating these from the higher requirement of inpatient facilities.
* These descriptions may not be complete and are provided for information only.
3; 4, 6; Table 6.4; Table 6.7.2;
7; 8; Table 8.1; 9; Table 9.1; 10, 11;
Informative Appendix D
This addendum includes changes originally made by published Addendum p to the 2017 edition of the standard.
Addenda can be downloaded at http://www.ashrae.org/technicalresources/
standards-and-guidelines/standards-addenda.
6.1.1; 6.3.2.2; 7.6; 8.6; Table 7.1; added Addendum m addresses changes made as the committee has reviewed and responded to informal and formal
July 31, 2020 (ASHRAE)
9.3; 11; Informative Appendix B
interpretation requests. Additionally, in recognition of the changes in the behavioral health care industry, the
July 28, 2020 (ASHE)
committee has sought to specifically provide guidance.
July 31, 2020 (ANSI)
a. Revised lab exhaust discharge requirements in coordination with ANSI/AIHA Z9.5
b. Updated the standard to allow recirculating room units in sterilizer equipment room
c. Expanded guidance to address behavioral and mental health patient areas, residential behavioral and mental
health patient rooms in coordination with the FGI
d. Revised Normative and Informative references in coordination with recent publications
n
m
Addendum Sections Affected
Table F-1 ANSI/ASHRAE/ASHE Addenda to ANSI/ASHRAE/ASHE Standard 170-2017
50
ANSI/ASHRAE/ASHE Standard 170-2021
In reviewing Addendum a, it was noticed the filter requirements listed for nursing homes are not consistent with
the informative appendix table for recommended filter efficiencies by space type. Resident rooms are noted as
requiring MERV-14 in the informative appendix as “Resident rooms in a skilled nursing area”, however other
resident spaces were assigned MERV-8 under the category of “Any room, inpatient or outpatient, where a patient
stays less than 6 hours including waiting rooms”. This is incorrect in that 1: residents are not patients; and 2:
residents frequently spend amounts of time exceeding 6 hours outside of their room in these areas of the facility.
Addendum r increases filtration in nursing homes to MERV-14. Prior to Addendum a, these spaces required a
MERV-13 filter.
6.4; Table 9.1
6.3.2; 7.2; Table 7.1 Footnote u
r
s
NOTE
October 30, 2020
(ASHRAE)
October 21, 2020 (ASHE)
October 30, 2020 (ANSI)
November 30, 2020
(ASHRAE)
November 2, 2020 (ASHE)
November 30, 2020 (ANSI)
Approval Dates
• ASHRAE Std. Comm.
• ASHRAE BoD
• ASHE
• ANSI
Approved addenda, errata, or interpretations for this standard can be downloaded free of charge from the ASHRAE Web site at www.ashrae.org/technology.
* These descriptions may not be complete and are provided for information only.
The committee has reviewed and identified that the standard could better address the varied conditions that arise in
planning, designing and implementing airborne infectious isolation rooms, an especially relevant issue as we
navigate the many challenges of a world-altering pandemic event. Addendum s specifically ensures that the
standard provides flexibility in treating the exhaust discharge arrangements from these spaces, in alignment with
CDC guidelines on this topic.
Section 6.4(i) is revised to not include Table 9.1 because in Table 9.1 the only spaces that do not permit room
recirculation are 100% exhaust spaces. The prohibition on room recirculation units within these spaces has less to
do with concern of access to room recirculation equipment and that equipment serving as a future source of
contaminants and more to do with the contamination within the space itself. The installation of filters downstream
of all wet air-cooling coils and the supply fan is not justified as a minimum requirement for the 100% exhaust
spaces.
Description of Changes*
Addendum Sections Affected
Table F-1 ANSI/ASHRAE/ASHE Addenda to ANSI/ASHRAE/ASHE Standard 170-2017
POLICY STATEMENT DEFINING ASHRAE’S CONCERN
FOR THE ENVIRONMENTAL IMPACT OF ITS ACTIVITIES
ASHRAE is concerned with the impact of its members’ activities on both the indoor and outdoor environment.
ASHRAE’s members will strive to minimize any possible deleterious effect on the indoor and outdoor environment of
the systems and components in their responsibility while maximizing the beneficial effects these systems provide,
consistent with accepted Standards and the practical state of the art.
ASHRAE’s short-range goal is to ensure that the systems and components within its scope do not impact the
indoor and outdoor environment to a greater extent than specified by the Standards and Guidelines as established by
itself and other responsible bodies.
As an ongoing goal, ASHRAE will, through its Standards Committee and extensive Technical Committee structure,
continue to generate up-to-date Standards and Guidelines where appropriate and adopt, recommend, and promote
those new and revised Standards developed by other responsible organizations.
Through its Handbook, appropriate chapters will contain up-to-date Standards and design considerations as the
material is systematically revised.
ASHRAE will take the lead with respect to dissemination of environmental information of its primary interest and
will seek out and disseminate information from other responsible organizations that is pertinent, as guides to updating
Standards and Guidelines.
The effects of the design and selection of equipment and systems will be considered within the scope of the
system’s intended use and expected misuse. The disposal of hazardous materials, if any, will also be considered.
ASHRAE’s primary concern for environmental impact will be at the site where equipment within ASHRAE’s scope
operates. However, energy source selection and the possible environmental impact due to the energy source and
energy transportation will be considered where possible. Recommendations concerning energy source selection
should be made by its members.
ASHRAE · 180 Technology Parkway NW · Peachtree Corners, GA 30092 · www.ashrae.org
About ASHRAE
Founded in 1894, ASHRAE is a global professional society committed to serve humanity by advancing the arts and
sciences of heating, ventilation, air conditioning, refrigeration, and their allied fields.
As an industry leader in research, standards writing, publishing, certification, and continuing education, ASHRAE
and its members are dedicated to promoting a healthy and sustainable built environment for all, through strategic
partnerships with organizations in the HVAC&R community and across related industries.
To stay current with this and other ASHRAE Standards and Guidelines, visit www.ashrae.org/standards, and
connect on LinkedIn, Facebook, Twitter, and YouTube.
About ASHE
The American Society for Health Care Engineering (ASHE) of the American Hospital Association is a trusted
professional resource that provides education, regulatory guidance, networking, advocacy representation, and
professional development for our members. ASHE is committed to our members, the facilities they build and
maintain, and the patients they serve.
For more information, visit ashe.org.
Visit the ASHRAE Bookstore
ASHRAE offers its Standards and Guidelines in print, as immediately downloadable PDFs, and via ASHRAE Digital
Collections, which provides online access with automatic updates as well as historical versions of publications.
Selected Standards and Guidelines are also offered in redline versions that indicate the changes made between the
active Standard or Guideline and its previous edition. For more information, visit the Standards and Guidelines
section of the ASHRAE Bookstore at www.ashrae.org/bookstore.
IMPORTANT NOTICES ABOUT THIS STANDARD
To ensure that you have all of the approved addenda, errata, and interpretations for this
Standard, visit www.ashrae.org/standards to download them free of charge.
Addenda, errata, and interpretations for ASHRAE Standards and Guidelines are no
longer distributed with copies of the Standards and Guidelines. ASHRAE provides
these addenda, errata, and interpretations only in electronic form to promote
more sustainable use of resources.
Product code: 86536
3/21