When it comes to protecting people from COVID-19, cleaning or filtering the air alone is not enough. But the good news is that HEPA filters can trap particles that contain coronavirus. People expel droplets of respiratory fluid, saliva, and possibly viruses into the air when they breathe, cough, and talk. Even if the water in the droplet evaporates, they contain salts, proteins, and other materials, in addition to any viruses, which means that the remaining particles are usually only a few microns in size, making them fairly easy to trap with a HEPA filter.
So how do HEPA filters and UV light air purifiers work? HEPA is the reference standard for air filtration, but non-HEPA filters can also help remove particulates from indoor air. The filters are designed to improve indoor air quality by physically removing tiny particles of matter that may be floating around, such as dust, pollen, and pet dander. A NASA study on HEPA filtration explains why HEPA filters are actually more efficient than other filters when it comes to capturing ultrafine particles below the 0.3 micron HEPA test standard. According to the study authors, the results suggest that air filters could be used to reduce the risk of patients and medical personnel contracting SARS-CoV-2 in hospitals.
This means that HEPA purifiers would efficiently capture viruses (and any droplets of saliva and mucus that contain them) that enter their filters. Air purifiers with HEPA filters or even lower quality filters can capture solid particles of virtually all sizes, including particles that are 0.1 micron in diameter, or the same size as the coronavirus. Research conducted in a hospital full of people with COVID-19 has confirmed that portable air filters effectively remove SARS-CoV-2 particles from the air. As the name suggests, these filters are great for taking things out of the air and holding them back so they can't be recirculated. Many media outlets have incorrectly stated that HEPA filters do not filter below 0.3 microns and therefore cannot capture airborne coronaviruses. However, air purifiers with HEPA filtration efficiently capture particles the size (and much smaller) of the virus that causes COVID-19, so the answer is yes.
They can filter viruses from the air in homes, offices, and schools, but other measures such as good hygiene and disinfectants must continue to be taken along with HEPA air purifiers.
