An air filter or separator is a device which removes contaminants (often solid particulates such as dust) from an air stream.

Air filters are used in applications where air quality is important, particularly in building ventilation systems and in engines such as internal combustion engines, gas compressors, diving air compressors, gas turbines, and others.

Another method uses fibers or elements with a static electric charge that attracts dust particles ( Electrostatic Precipitator).