When used correctly, air and HVAC filters can help reduce airborne contaminants, including viruses, in a small building or space. People expel droplets of respiratory fluid, saliva, and possibly virus into the air when breathing, coughing, and talking. Even if the water in the droplet evaporates, the droplets contain salts, proteins, and other material in addition to any viruses, which means that the remaining particles are usually a few microns in size, making them quite easy to catch with a HEPA filter. A HEPA filter doesn't kill the COVID-19 virus, but items that can carry the virus stick to the filter so they can't circulate in your living area.
HEPA stands for “high-efficiency particulate air”. A true HEPA filter can be used in purifiers throughout the house to make the air cleaner and less polluted. In this study, the use of HEPA air purifiers in a conference room significantly reduced the exposure of nearby participants and a speaker to airborne particles produced by a simulated infected participant. Using two HEPA air purifiers near the aerosol source reduced aerosol exposure for uninfected participants and speakers by up to 65%.
When used together, air filters and HEPA masks reduced exposure to respiratory aerosols by up to 90%. Research at a hospital flooded by people with COVID-19 has confirmed that portable air filters effectively remove SARS-CoV-2 particles from the air, the first such evidence in a real environment. The combination of the two HEPA air filters and universal masking reduced total exposure by up to 90%. The team found SARS-CoV-2 particles in the air when the filter was turned off, but not when it was turned on.
Make sure your home's forced air system filter is properly sized to prevent air leaks around the filter. Use the highest-efficiency particulate filter that the forced air system is able to handle, without impeding airflows. Researchers collected air samples from the rooms for a week when the air filters were on and two weeks when they were turned off. You can also get high-quality HEPA air filters from large home improvement stores, but the selection is likely to be limited.
A true HEPA filter is not as powerful as a medical grade HEPA filter, but it meets the HEPA rating by removing at least 99.7% of 0.3 micron particles.