Another allergy filter

Another type is the activated carbon filter that helps to remove gases, odors and toxins from indoor air.
In such a filter, chemicals, gases, and odors stick to the carbon and are "adsorbed" onto its huge surface area, bonding to the surface through chemical attraction. An electrostatic filter ionizes particles as they are passed over an electronic cell, after which they are attracted and trapped by oppositely charged collector plates.
A number of ionization air filters have been found to generate ozone, which is a proven health hazard and lung irritant. The Environment Protection Agency (EPA) has come out strongly against the use of ozone generators as air filters.