🏥 ASHRAE 170
Ventilation of Health Care Facilities — Minimum design parameters for space ventilation by room type and edition.
Key Pressure Differential Requirements
AII Room (Airborne Infection Isolation)
−0.01 in. WC
−2.5 Pa minimum negative differential to adjacent areas. Permanently installed pressure monitoring required. All air exhausted directly outdoors (or through HEPA to general exhaust). Minimum 12 total ACH / 2 OA ACH.
PE Room (Protective Environment)
+0.01 in. WC
+2.5 Pa minimum positive differential to adjacent areas. Permanently installed pressure monitoring required. HEPA filtration. Constant-volume airflow required. Minimum 12 total ACH / 2 OA ACH.
Operating Room / Class 3 Imaging
+0.01 in. WC
+2.5 Pa minimum positive to all adjoining spaces at all times. Individual temperature control required. Unidirectional downward supply diffuser array. Minimum 20 total ACH / 4 OA ACH.
Bronchoscopy / Autopsy / Morgue
−0.01 in. WC
−2.5 Pa minimum negative differential to adjacent spaces with other functions. All air exhausted directly to outdoors — no mixing with other exhaust systems. Low-sidewall exhaust grilles required for autopsy.
AII/PE Combination Room
± 0.01 in. WC
Two permanently installed pressure monitors required. HEPA filtration. Anteroom required — can be positive or negative relative to both the AII/PE room and corridor. No reversible airflow permitted.
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CONSTRUCTION YEAR LOOKUP
Enter the year a space was constructed or last renovated to automatically identify the applicable edition and view its required ventilation parameters.
NR = No Requirement. Footnote references abbreviated; consult ANSI/ASHRAE/ASHE Standard 170 for full normative notes and exceptions. Additional editions will be added as PDFs are provided. * = footnote applies — see standard.