ASHRAE 170 Edition Tracker: Which Version Applies to Your Facility (2008–2025)

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Short answer: The current edition is ANSI/ASHRAE/ASHE Standard 170-2025, and the 2026 FGI Codes incorporate it, including all issued addenda (HFM Magazine). The edition your building must meet is the one your state or local authority having jurisdiction (AHJ) has adopted, and ASHE notes that AHJs have adopted and are enforcing different editions. For Medicare hospitals, CMS enforces NFPA 99-2012, which The Joint Commission describes as including the 2008 edition of ASHRAE 170. Confirm your edition in writing for every project.

Current edition at a glance

  • Current edition: ANSI/ASHRAE/ASHE Standard 170-2025, Ventilation of Health Care Facilities, published in 2025 by ASHRAE in partnership with ASHE (ASHE).
  • Errata: ASHRAE’s errata sheet dated April 14, 2026 applies to the first printing and adds items to an earlier errata sheet dated March 23, 2026.
  • Addenda to 170-2025: ASHRAE’s addenda listing shows two so far, Addendum v and Addendum y, both dated September 23, 2026. What they change is summarized under How addenda work.
  • Older editions still in use: ASHE still lists the 2021, 2017 and 2008 editions and tells readers to connect with their AHJ to determine which edition to follow.

Edition timeline: 2008 to 2025

Each row lists only changes that a public source states. The standard itself is sold by ASHRAE and ASHE, so the summaries credit the page that describes the change.

Edition Key changes reported by public sources Source
170-2008 First edition. ACHR News reports that, according to ASHRAE, it was the first ANSI standard to specifically address ventilation in health care facilities. Addendum d, approved in July 2010, lowered the minimum design relative humidity for operating rooms and other short-term patient treatment spaces from 30% to 20%. ACHR News (2013); ACHR News on Addendum d
170-2013 Published December 2013. Specifically addresses energy recovery, provided it allows no cross-contamination of exhaust air back to the supply airstream. Updates and clarifications on humidity, ducted returns, recirculating room units and duct lining. Permits some use of plenum returns in outpatient facilities. ACHR News, Dec 26, 2013
170-2017 Began dividing requirements into hospital, outpatient and residential categories (FGI calls this “the beginning of the process”). Added adiabatic humidifiers as an acceptable humidifier type, a new lower-requirement exam room type, and clarified that controls to change pressure relationships are prohibited for all spaces. Operating room design relative humidity is 20% minimum and 60% maximum. FGI 2018 summary; ACHR News (2018); ASHRAE TC 9.6 white paper
170-2021 Incorporated 17 addenda to the 2017 edition. Allows airborne infection isolation (AII) room exhaust to discharge to general exhaust under certain conditions. Extensive revisions to air filtration, with new ventilation-table columns for filtration and unoccupied turndown. Extensive changes to the outpatient and residential sections. Expanded intake and exhaust separation guidance. Improved behavioral and mental health guidance. ASHRAE, May 11, 2021
170-2025 (current) Optional natural ventilation. Outdoor air calculated at the system level for systems serving both Standard 170 and Standard 62.1 spaces. Updated Class 2 and Class 3 imaging requirements. Clarified outpatient unoccupied turndown. Reorganized requirements for ventilation during construction. Updated cooling and heating reserve capacity and on-site fuel requirements. New behavioral health space types, clarified bronchoscopy requirements, and new space types coordinated with FGI 2026. ASHE 170-2025 page

For a plain-English walk-through of the 2021 and 2025 changes, see what changed in recent editions of ASHRAE 170.

How addenda and continuous maintenance work

ASHRAE keeps Standard 170 under continuous maintenance, which, in FGI’s words, permits official changes to be made at any point over the life cycle of the document. Approved changes are published as lettered addenda. ASHRAE’s addenda listing shows, for example, addenda to the 2021 edition running from Addendum c (July 30, 2021) to Addendum w (July 31, 2025). A new edition folds in the addenda published before it: ASHRAE says the 2021 edition incorporates 17 addenda to the 2017 edition.

Corrections to the printed text are issued separately as errata. ASHRAE’s errata listing shows one current errata sheet for 170-2025, dated April 14, 2026.

The two addenda to 170-2025 so far, both approved by ASHRAE and ANSI on September 22, 2026, do the following, according to their published forewords:

  • Addendum v: adds equivalences between MERV ratings (ASHRAE Standard 52.2) and ISO 16890 filter classes for the minimum filtration Standard 170 requires, to help users outside the United States.
  • Addendum y: follows research on operating room testing and balancing data from 45 hospitals and 521 operating rooms. The committee recommends a risk assessment before making operational adjustments to operating room ventilation, and, per the foreword, adds new related notes to Tables 7-1 and 8-1.

FGI treats later addenda as part of its documents. For the 2022 hospital Guidelines, FGI states that published addenda to ASHRAE Standard 170-2021 shall be considered part of the 2022 Guidelines. If your project runs over several years, track the addenda, not just the edition year.

FGI pairings: which 170 edition each FGI edition contains

FGI has incorporated Standard 170 into its Guidelines since the 2010 edition, so a state that adopts an FGI edition also takes in the 170 edition that FGI document contains. See FGI 2022 vs 2026 and our FGI Guidelines overview for the wider changes.

FGI document ASHRAE 170 edition included Source
2010 Guidelines 170-2008. FGI states that Standard 170 has been incorporated into the Guidelines beginning with the 2010 edition. FGI 2018 summary; ACHR News
2014 Guidelines (Hospitals and Outpatient Facilities) 170-2013, with all addenda approved through November 2013, as Part 4. FGI 2014 summary
2018 Guidelines 170-2017, with all addenda approved through November 2017, as Part 3. Addenda issued after the 2017 edition count as part of the 2018 documents. FGI 2018 summary
2022 Guidelines (Hospitals) 170-2021, dated November 2021, which incorporates addenda c and d. Later published addenda count as part of the 2022 Guidelines. FGI 2022 summary
2026 FGI Codes (released August 31, 2026) 170-2025, including all issued addenda. FGI’s 2026 hospital handbook lists 170-2025 as included content. HFM Magazine; FGI press release; FGI OneSource

For how the two documents divide the work, see how ASHRAE 170 interacts with FGI Guidelines.

What CMS and The Joint Commission enforce

CMS. The hospital Conditions of Participation require hospitals to meet the Health Care Facilities Code (NFPA 99) and its Tentative Interim Amendments, and the regulation incorporates the 2012 edition of NFPA 99 by reference. CMS adopted the 2012 NFPA 99 and NFPA 101 effective July 5, 2016, and began surveying to them on November 1, 2016 (CMS Survey and Certification letter 16-29). NFPA 99 TIA 12-2, which CMS also adopted, added a chapter on HVAC stating that systems serving covered spaces “shall be provided in accordance with ASHRAE 170” (NFPA 99-2012, 9.3.1.1). 42 CFR 482.41 itself does not name an ASHRAE 170 edition. For the life safety side of the same rule, see which NFPA 101 edition CMS enforces.

Which 170 edition does NFPA 99-2012 point to? The Joint Commission’s September 2026 Survey Tools Guide says heating, cooling and ventilation follow “NFPA 99-2012, which includes 2008 ASHRAE 170, or state design requirements if more stringent”. We have not yet confirmed this edition reference in the text of NFPA 99 itself.

The Joint Commission. In the hospital Survey Tools Guide issued September 2, 2026, critical-area ventilation is scored under PE.04.01.01 EP 3, formerly EC.02.05.01 EP 15, mapped to CMS CoP 482.41(d)(4). The EP reads: “In critical care areas designed to control airborne contaminants (such as biological agents, gases, fumes, dust), the ventilation system provides appropriate pressure relationships, air-exchange rates, filtration efficiencies, temperature and humidity.” Its notes apply NFPA 99-2012 to new and existing facilities and to altered or renovated systems with construction or plans approved on or after July 5, 2016. The Joint Commission’s utility systems web page still shows the former number, EC.02.05.01 EP 15.

State adoption: how to confirm your edition locally

FGI’s adoption map reports that, as of August 31, 2026, 42 states have adopted some edition of the FGI Codes or Guidelines, 3 allow FGI as an alternate path to compliance in some instances, and 5 do not use them in any official capacity. Because each FGI edition carries a specific 170 edition, the FGI edition your state adopted points to the 170 edition you are likely to be held to.

  1. Ask the state licensing agency which FGI edition it enforces for your facility type. FGI notes that the state health department licensing entity is typically the AHJ. See which FGI edition your state enforces.
  2. Check the state or local mechanical code. Some jurisdictions also reference ventilation requirements through their mechanical code. Ask the code official which edition of ASHRAE 170, if any, the mechanical code references.
  3. Check for exceptions. FGI reports that 5 states (Kansas, Maine, Mississippi, New Hampshire and New York) permit use of a more recent FGI edition than the one adopted in some instances.
  4. Get the answer in writing for each project, naming the FGI edition, the 170 edition and any addenda the AHJ will apply.

Still being verified

Which edition of ASHRAE 170 each edition of the International Mechanical Code references, and where. We will add it once we can confirm it from a public ICC source.

Existing vs new construction

New editions generally reach existing buildings only when you build, alter or renovate. NFPA 99-2012’s HVAC chapter applies to new construction and to altered, renovated or modernized portions of existing systems, and existing construction or equipment may continue in use when it does not constitute a distinct hazard to life. The Joint Commission’s Survey Tools Guide adds that existing facilities may comply with the 2012 NFPA 99 ventilation requirements or the edition CMS had adopted when the system was installed, for example the 1999 NFPA 99.

CDC’s environmental infection control guideline says to ensure that existing structures continue to meet the specifications in effect at the time of construction. For AII rooms, CDC sets at least 12 air changes per hour (ACH) for new and renovated rooms and at least 6 ACH for existing rooms, and continuous negative pressure of 2.5 Pa (0.01 in. water gauge) relative to the corridor. ASHE’s 2021 ventilation guidance states that rooms constructed before 2005 may operate at -0.001 in. of water (-0.25 Pa) and 6 ACH. For full isolation room specifications, see ASHRAE 170 requirements for airborne infection isolation rooms.

Under CMS Survey and Certification letter 16-29, buildings constructed, or given design approval or building permits, before July 5, 2016 can meet Existing Occupancy requirements. All other construction must meet New Occupancy requirements.

Change log

Date Change
October 2026 Tracker created. Current edition 170-2025; errata sheet dated April 14, 2026; Addenda v and y to 170-2025 (September 23, 2026) listed and summarized; FGI pairings 2010 to 2026; CMS and Joint Commission enforcement with the current PE.04.01.01 EP 3 numbering.

FAQ

What is the current edition of ASHRAE 170?

The current edition is ANSI/ASHRAE/ASHE Standard 170-2025, published in 2025 by ASHRAE with ASHE. An errata sheet dated April 14, 2026 corrects its first printing, and ASHRAE has published Addenda v and y to it. See ASHE’s 170-2025 page.

Which ASHRAE 170 edition does my hospital have to meet?

Your hospital has to meet the edition your state or local AHJ has adopted, usually through the FGI edition it enforces, plus whatever CMS and your accreditor survey to. ASHE notes that AHJs are enforcing different editions, so confirm the edition in writing for each project.

Does CMS enforce ASHRAE 170?

CMS enforces ASHRAE 170 indirectly. Hospitals must meet NFPA 99-2012, and NFPA 99 TIA 12-2, which CMS adopted, requires HVAC systems serving covered spaces to be provided in accordance with ASHRAE 170.

Which ASHRAE 170 edition does NFPA 99-2012 reference?

The Joint Commission’s September 2026 Survey Tools Guide describes NFPA 99-2012 as including the 2008 edition of ASHRAE 170, with state design requirements applying if they are more stringent.

Which Joint Commission standard covers critical-area ventilation now?

The Joint Commission’s hospital Survey Tools Guide issued September 2, 2026 scores critical-area ventilation under PE.04.01.01 EP 3, which it marks as formerly EC.02.05.01 EP 15. It covers pressure relationships, air-exchange rates, filtration efficiencies, temperature and humidity.

Which ASHRAE 170 edition is in the 2026 FGI Codes?

The 2026 FGI Codes for Planning and Design incorporate ASHRAE 170-2025, including all issued addenda, according to HFM Magazine.

What is an ASHRAE 170 addendum?

An addendum is an official change to Standard 170 published between editions under ASHRAE’s continuous maintenance process. The next edition folds addenda in, and FGI treats later published addenda as part of its documents.

Do existing AII rooms need 12 air changes per hour?

Not under CDC’s guideline. CDC sets at least 12 ACH for new and renovated AII rooms and at least 6 ACH for existing AII rooms. Your AHJ may require more, so check the edition it enforces.

Sources

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