Even when school is closed, air quality is important to maintaining a healthy indoor environment. Now that we are implementing reopening strategies, it’s imperative that we do all we can to protect students, teachers, and staff—and the families they will be going home to.
school building hallway

While social distancing and face masks are still the most important protective measures against the spread of COVID-19 in schools, ventilation systems offer opportunities for prevention as well. The CDC and other advisory groups recommend that we “Improve central air filtration to the MERV-13* or the highest compatible with the filter rack, and seal edges of the filter to limit bypass.”¹

CDC Guidelines for Schools and Public Buildings

In addition to upgrading and changing filters, allow as much fresh air into the school building from outside as possible, increase ventilation rates and let systems run longer hours (24/7 if possible). Check filters periodically to ensure they are within service life and appropriately installed. In general, disabling of heating, ventilating, and air-conditioning systems is not recommended to reduce transmission of the virus, even when occupancy is low.²

“Ventilation and filtration provided by heating, ventilating, and air-conditioning systems can reduce the airborne concentration of SARS-CoV-2 [COVID-19] and thus the risk of transmission through the air. ”²

An open letter to the World Health Organization, published in Clinical Infectious Diseases and signed by 239 researchers, calls for attention and guidance regarding tiny respiratory particles that float in the air, called aerosols, that could infect someone who breathes them in. “Hand-washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people.”

“They’ll continue to float and follow the air streams in a room,” says Kimberly Prather, an atmospheric chemist at Scripps Institution of Oceanography, who signed the letter to WHO.4

The coronavirus is about 500 times smaller than the width of a human hair, which measures around 50 microns or more. That’s exceedingly tiny, but the virus would be traveling in somewhat larger aerosol particles, making it easier to be caught by filters.¹

The Importance of Indoor Air Quality in Schools

Particularly in schools, where children may not fully understand the concept of contagion, social distancing and the use of face masks may be difficult to enforce. That’s why it’s so important to operate the best possible HVAC scenario for your public space: it’s a safety measure that’s completely within the control of building management, independent of the behavior of children. Proper air filtration will not only help protect children attending school under unfamiliar circumstances, but also enhance safety for teachers and administrators who come in contact with students in large groups, and the friends and family members they will go home to at the end of the day.

*MERV = minimum efficiency reporting value


²https://www.ashrae.org/about/news/2020/ashrae-issues-statements-on-relationship-between-covid-19-and-hvac-in-buildings; https://www.ashrae.org/news/ashraejournal/guidance-for-building-operations-during-the-covid-19-pandemic


4 Airborne Transmission of COVID-19 

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