Filters that are installed and maintained well capture harmful particles and microorganisms, which lowers the risk of transmission indoors. High-efficiency particulate air (HEPA) filters have been shown to be particularly effective at capturing airborne viruses.
Can’t afford a commercial air filter? You can easily build one yourself.
Filters pair well with far UV-C lamps: the lamps work on viruses and bacteria in the air, and the filter catches particles, including those the lamps’ ozone helps form.