CDC reports on portable air cleaners, masking for reducing indoor exposure to SARS-CoV-2 aerosols

July 6, 2021

The Centers for Disease Control and Prevention (CDC) study on the use of HEPA air cleaners in a conference room found they significantly reduced the exposure of nearby participants and a speaker to airborne particles produced by a simulated infected participant, released the CDC in its Morbidity and Mortality Weekly Report.

The air cleaners were most effective when they were located in the center of the room close to the aerosol source. Moreover, the combination of HEPA air cleaners and universal masking was more effective than was either intervention alone. The use of masks without air cleaners reduced the aerosol exposure of the receivers by 72%, and the use of air cleaners without masks reduced the exposure by up to 65%. When used together, the HEPA air cleaners and masks reduced exposure to respiratory aerosols by up to 90%.

These findings suggest that the use of portable HEPA air cleaners and universal masking can each reduce exposure to simulated SARS-CoV-2 aerosols in indoor environments, with larger reductions occurring when air cleaners and masking are used together.

A simulated infected meeting participant who was exhaling aerosols was placed in a room with two simulated uninfected participants and a simulated uninfected speaker. Using two HEPA air cleaners close to the aerosol source reduced the aerosol exposure of the uninfected participants and speaker by up to 65%. A combination of HEPA air cleaners and universal masking reduced exposure by up to 90%.

Ventilation is a well-established method for reducing potential exposures to infectious aerosols. By removing airborne particles from a room, ventilation systems can reduce exposures that occur by inhalation of infectious aerosols, deposition on susceptible mucous membranes, or conveyance to mucous membranes by contaminated hands. However, in most nonclinical settings, ventilation systems are designed only with sufficient airflow to provide fresh air while maintaining comfortable temperature and humidity levels; these systems typically are not designed to have the much higher airflow rates that are needed to reduce disease transmission.

During the ongoing pandemic, public health and professional organizations have provided guidance for increasing ventilation and air filtration to decrease the spread of SARS-CoV-2. One recommended option, especially when existing HVAC systems might be insufficient, is adding portable HEPA air cleaners to rooms. The results of this study support the use of portable HEPA air cleaners to reduce exposure to airborne particles.

CDC has the report.

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