These filters were designed to capture 90% of large allergens like pet dander and mould spores from the air passing through the filter. They're even effective against microscopic allergens like smog, dust, smoke, bacteria, and particles that may carry viruses. No unnecessary antimicrobial chemicals added to this model. Plus, the filtering material prevents the growth of bacteria, fungi, mildew, and mould in normal use. Each filter can last up to 3 months. This product complies to the American Lung Association Health House Indoor Air Quality Guidelines.