Portable air cleaners could reduce exposure to SARS-CoV-2 aerosols, study finds

The use of portable air cleaners could reduce indoor exposure to SARS-CoV-2 aerosols, newly reported study findings suggest.

In a simulation, researchers found that portable high-efficiency particulate air (HEPA) cleaners and masks both reduced exposure to SARS-CoV-2 when used individually. Used together, they reduced exposure by up to 90%, according to the study, which was published in MMWR.

“To reduce indoor transmission of SARS-CoV-2 between persons, CDC recommends measures including physical distancing, universal masking and increased room ventilation,” William G. Lindsley, PhD, a research biomedical engineer in the CDC’s Health Effects Laboratory Division, and colleagues wrote. “Ventilation systems can be supplemented with portable HEPA cleaners to reduce the number of infectious particles in the air and provide enhanced protection from transmission between persons.”

Lindsley and colleagues used respiratory simulators "to mimic a person with COVID-19 and other, uninfected persons in a 584-square-feet conference room.” The simulator mimicked a person exhaling infectious particles, and three breathing simulators mimicked a speaker and two participants exposed to these aerosol particles, Lindsley and colleagues explained.

Two HEPA air cleaners were placed in four different locations during the study — the center of the room on the floor behind the source simulator, on the left and right sides of the room on the floor, on left and right sides of the room and elevated 32 inches, and in the front and back of the room on the floor.

The researchers also placed three-ply cotton cloth face masks on the breathing simulators and conducted experiments either with all simulators unmasked or all simulators masked to represent universal masking.

According to the study, the two HEPA air cleaners reduced overall exposure to simulated exhaled aerosol particles by up to 65% without universal masking, whereas universal masking reduced the combined mean aerosol concentration by 72% without the use of the filters. The combination of the air cleaners and universal masking reduced overall exposure by up to 90%, Lindsley and colleagues said.

The researchers found that the air cleaners were most effective when they were in the center of the room and close to the aerosol source.

“These findings support the utility of portable HEPA air cleaners and universal masking for reducing exposure to indoor aerosols containing SARS-CoV-2,” the authors wrote. “Efforts to reduce SARS-CoV-2 aerosol exposure could help limit transmission of the virus and decrease incidences of COVID-19 illness and death