An air filter is usually made of a spun fiberglass material or from pleated paper or cloth enclosed in a cardboard frame. Its basic function is to clean the air that circulates through your heating and cooling system. Filters trap and hold many types of particulates and contaminants that could affect your health and comfort, including:
Dust and dirt
Mold and mold spores
Fibers and lint
Metal, plaster or wood particles
Hair and animal fur
Bacteria and microorganisms
Filtration usually occurs when expended air is brought back into the HVAC equipment to be conditioned and distributed again. The air is forced through the filter, and the material removes particulates and other contaminants from the air.