ASHRAE 170 room conditions, logged space by space
ASHRAE/ASHE Standard 170 sets ventilation design for health care spaces: pressure, air changes, filtration, humidity and temperature by room type. Surveyors then ask whether rooms still perform as designed. Aqueduct logs pressure, temperature, humidity and air handler status per room and flags every excursion.
Who it applies to
Hospitals and outpatient facilities in their design and renovation. The current edition is 170-2025. For existing US hospitals, CMS and The Joint Commission enforce it indirectly, through the health care facilities code. Which edition applies depends on the authority having jurisdiction.
Design parameters that need operating records
Values from published addenda to 170-2021 and 170-2025. Your engineers and accrediting body decide compliance.
| Requirement | What it asks for | Data Aqueduct supplies |
|---|---|---|
| Operating room (Table 7-1) | Positive pressure, 4 outdoor and 20 total air changes per hour, MERV-16, 20 to 60 percent RH, 68 to 75°F. | Differential pressure, temperature and humidity per room, with excursions timestamped. |
| Airborne infection isolation (Table 8-1) | Negative pressure, 12 total air changes, all air exhausted outdoors, RH at most 60 percent. | Room pressure monitors read continuously, with reversals flagged. |
| Protective environment (Table 8-1) | Positive pressure, 12 total air changes, HEPA filtration. | Pressure and filter differential points from the BMS. |
| Air changes | Supply and exhaust airflow meeting the design rate for each space. | Airflow points trended per room where the BMS has them; test and balance stays with your contractor. |
| Operational changes, note ii (2026) | A documented risk assessment before ventilation is adjusted, kept in a ventilation management plan. | Before and after records for any change to a room's air. |
What changed in 2026
Operating rooms in 45 hospitals where higher ventilation did not lower surgical site infection, cited in addendum y, which adds the risk assessment rule.
Source: ASHRAE 170-2025 addendum yRelated standards
Sources4 references cited on this page
sites in 21 countries run on Aqueduct.
and 9 clinics in one of India’s top hospital chains.
US airport running water intelligence on Aqueduct.
of commercial real estate under Aqueduct.
FMCG manufacturing campus.
operations run on Aqueduct.
Related
Common questions
No. ASHRAE 170 sets design values for each room type rather than monitoring rules. Continuous room records are how a hospital shows those values still hold between surveys and rebalancing, and Aqueduct logs each room so any drift has a date and a duration.
Only with owner approval, and many hospitals keep critical rooms read-only. Under the 2026 note, any change to space ventilation needs a documented risk assessment first, so Aqueduct logs the readings either side of any adjustment the hospital approves.
For CMS-certified hospitals, the one referenced through NFPA 99-2012, which is 170-2008. New projects follow the edition the local code or FGI Guidelines adopt, so one hospital can hold rooms built to different editions, and Aqueduct stores the limits per room.
Yes. Aqueduct flags the moment an airborne infection isolation room loses its negative relationship to the corridor. The alert carries the room, the duration and the air handler state at the time, so engineering starts from the likely cause. See Joint Commission PE.
See Aqueduct on your own facility.
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