Source: Jones et al., 2020. Schools for Health: Risk Reduction Strategies for Reopening Schools. HarvardHealthy Buildings Program. https://schools.forhealth.org. The Healthy Buildings Program at the Harvard T.H. Chan School of Public Health recently published an article that provides a multi-layer strategy to reduce the risk of transmission of COVID-19 through the use of portable air purifiers in public buildings. According to their experts, the first steps in preventing the airborne spread of the virus are to outfit the building’s ventilation system with filters that can screen out the virus and to open windows, which can provide a supply of fresh, virus-free outside air. A final step would be to use a portable HEPA (high-efficiency particulate air) air purifier to remove virus particles from the air. PORTABLE AIR CLEANERS (PACS), ALONG WITH OTHER ENGINEERING CONTROLS, CAN BE USED TO REDUCE AIRBORNE CONCENTRATIONS OF SARS-COV-2. Portable air cleaners and HVAC filters can reduce indoor air pollutants that are airborne including viruses. By themselves, portable air cleaners and HVAC filters are not enough to protect people from the virus that causes COVID-19. When used along with other best practices recommended by CDC and others, filtration can be part of a plan to protect people indoors.