©2025 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 67, No. 6, June 2025.
Bridging the Gaps: Mapping Space Types Across ASHRAE Standards 62.1, 170, & 241
By Meghan K. McNulty, Travis English, Marwa Zaatari
Meghan K. McNulty, P.E., is a building systems engineer with Pacific Northwest National Laboratory. Travis English, P.Eng. is a senior director of engineering at Kaiser Permanente. Marwa Zaatari, Ph.D., is chief science officer of DZine Partners and head of product at Poppy.
ASHRAE Standard 241-2023, Control of Infectious Aerosols, sets minimum requirements to reduce the risk of disease transmission by infectious aerosols. The standard mandates compliance with indoor air quality (IAQ) standards, including ANSI/ASHRAE Standards 62.1, 62.2 and ANSI/ASHE/ASHRAE Standard 170. Standard 241 introduces an operating mode for times of high risk—called infection risk management mode (IRMM)—and defines minimum equivalent clean airflow rates for infection control (ECAi). These rates have units of airflow per person (cfm/person or L/s/person). Problematically, the rates cover 25 types of commercial, residential and health-care spaces that do not directly align with the 278 occupant categories defined in Standards 62.1 and 170. To resolve this, the Standard 241 working body, SSPC241, mapped Standards 62.1 and 170 onto Standard 241. This column presents the mapping and discusses its implications.
Applying ASHRAE Standard 241-2023 alongside Standards 62.1 and 170 is a challenge. If a specific occupancy from Standard 62.1 or 170 is not listed in Standard 241’s Table 5-1, Minimum Equivalent Clean Airflow per Person in Breathing Zone in IRMM, users are instructed to select the “most similar” occupancy category. Some occupancy categories—like “classrooms”—align directly. However, many spaces—like “daycare sickroom”—lack clear matches.
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