The Bio-Fighter® Germicidal UV Light works with your air filter to clean your homes indoor air.While your air filter captures particulate contaminants, the Bio-Fighter® Germicidal UV Light works to reduce biological contaminants. But unlike air filters, which are only effective when your heating & cooling system is running, the Bio-Fighter® works 24 hours a day, 7 days a week, disinfecting cooling coils, drain pans, and air ducts exposed to the germicidal UV light...even when your heating & cooling system isn't running!