Our top-of-the-line filter captures 99.97% of airborne particles from the air passing through the filter media, including dust, allergens, bacteria and viruses. Designed with electrostatic air filtration, the Filtrete True HEPA Filter traps particles 1000x smaller than the human eye can see. Say hello to cleaner, fresher indoor air. (As small as 0.3 microns, from the air passing through the filter media. Initial efficiency value.)