HEPA air purifiers work well against airborne particles by capturing them in the HEPA filter. It filters out 99.97% airborne particles including pollen, dust, and other pollutants. To a degree, HEPA air purifiers are able to efficiently block the particles that are virus-sized. But there are no studies to date with that air purifiers are able to help protect against infection. So please follow the CDC's recommendations to help prevent COVID-19: wash your hand, clean and disinfect frequently.