An air filter is a device that removes solid particulate matter (such as dust, pollen, and smoke), gaseous pollutants (such as odors and some chemical gases), or microorganisms (such as bacteria and mold spores) from flowing air through physical interception, adsorption, or other means. Its core component is a filter (such as a HEPA filter or activated carbon filter). As air is forced through, pollutants are captured by the filter material, resulting in cleaner air. It is widely used in air conditioning systems, air purifiers, automotive interiors, cleanrooms, and industrial production, effectively improving indoor air quality, protecting health, or meeting specific process requirements.