How ASHRAE Standard 241 Controls Infectious Aerosols

The U.S. Green Building Council’s Center for Green Schools and the Efficient and Healthy Schools Program co-hosted a webinar titled “Unanswered Questions: ASHRAE 241 and CDC Ventilation Guidance for Schools” in the spring. The event brought together members of the ASHRAE 241 committee and the Centers for Disease Control and Prevention (CDC) to discuss their latest ventilation guidelines for school buildings.

ASHRAE Standard 241 sets a baseline focused on mitigating the risk of disease transmission in new and existing buildings. The standard emphasizes the importance of preventative maintenance, enhanced filtration, and regular building assessments as key components of building readiness planning for infection control.

Dr. Marwa Zaatari, a committee member of ASHRAE 241 and representative of DZine Partners, emphasized that while ASHRAE Standard 241 is not a required building code, schools can go above and beyond and the ventilation mechanical code.

“The benefits are huge,” she said. “In fact, from AIHA, they estimate a cost benefit ration of improving indoor air quality is between 18 to 47. So for every $1 you spend on improving indoor air quality can get up to $47 back from a health and productivity perspective.”

ASHRAE supports multiple bills that were recently introduced in Congress that would improve school indoor air quality through incentives and voluntary measures; establishing monitoring and indoor air quality technical assistance for schools. 

“Standard 241, is it required? No, but I think it should be desired. This is a really powerful tool,” added Meghan McNulty, another ASHRAE 241 committee member from the Pacific Northwest National Laboratory, noted that any organization can use this standard. “We’ve had all this guidance of things you could do, you should do, you might want to do to reduce the risk of disease transmission, but this is the first time we’re saying this is the amount of clean air that you need to provide “

The panelists highlighted that implementing the principles of ASHRAE Standard 241 doesn’t have to break the bank. Many of the strategies recommended to achieve target equivalent clean airflow (ECA) rates and reduce airborne viral transmission – such as effective heating, ventilation, and air-conditioning maintenance and operation; filter replacements; and retrocommissioning – result in energy savings and improved system performance.

“Just adding a MRF 13 will be very close to being compliant with standard 241,” Zaatari said of lower occupancy schools.

“We can compare all these different strategies and use them interchangeably,” McNulty added. 

Kenneth Mead from the CDC’s National Institute for Occupational Safety and Health, speaking for himself and his family, which includes an educator, said there’s good reason to follow ASHRAE 241.

“If we can get to think beyond the dollars and cents of this first cost, which is many times subsidized by the government anyway, if we can get (schools) to think beyond that and to be smart in their selection for intervention, I think that there will be a long term payback,” Mead said.

ASHRAE Standard 241 can even be used by schools to reduce risk at specific times, Mead concluded, such as when schools are back in session after a break, during respiratory virus season, or when absenteeism rates increase due to illness.

Listen to the full webinar here.