By-3MFiltrete 3M Filtrete Micro Allergen HVAC Filter Electrostatic micro particle air filter Electrostatically charged inFiltrete in fibers attract and hold particles like magnets Captures microscopic allergens including dust smoke and smog particles Captures large allergens including mold spores and pet dander No antimicrobial added will not support the growth of bacteria mold mildew or fungi in normal use No monthly washing required Use in furnace or A/C for full three months of air quality protection under normal conditions Meets the American Lung Association and its Health Project Indoor Air Quality Guidelines Fiberglass filters were originally developed to protect your furnace and/or air conditioning system They were not intended to significantly improve your indoor air quality Filtrete filters do both They improve your indoor air quality by attracting and capturing allergy-aggravating microparticles and help keep your furnace equipment clean Air in your home is continually re-circulated through the filter and is cleaned with each pass through the filter Filters are generally disposable washable or vacuumable Follow the manufacturers guidelines for how often to change wash or vacuum your filter Note that cleaning a washable filter requires you to handle the dirty filter - exposing you to dirt and any captured allergens A disposable results in much less exposure - just put it in the trash