A particulate air filter is a device composed of fibrous or porous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) may also remove odors and gaseous pollutants such as volatile organic compounds or ozone. Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines.
Air filters typically consist of a sturdy frame, filled with some type of filter media, which is sealed to prevent leaks between the frame and media. Some filters may also have a faceguard — a screen attached to the filter to protect the media during handling — and/or a gasket to prevent leaks between the filter frame and its housing.