Gaseous Pollutant Removal

Gas-phase air filters remove gases and odors by using a material called a sorbent, such as activated carbon, which adsorbs the pollutants. These filters are typically intended to remove one or more gaseous pollutants from the airstream that passes through them. Because gas-phase filters are specific to one or a limited number of gaseous pollutants, they will not reduce concentrations of pollutants for which they were not designed. Some air cleaning devices with gas-phase filters may remove a portion of the gaseous pollutants and some of the related hazards, at least on a temporary basis. However, none are expected to remove all of the gaseous pollutants present in the air of a typical home. For example, carbon monoxide is a dangerous gaseous pollutant that is produced whenever any fuel such as gas, oil, kerosene, wood, or charcoal is burned, and it is not readily captured using currently available residential gas-phase filtration products.

Particle Removal

Two types of air cleaning devices can remove particles from the air -- mechanical air filters and electronic air cleaners. Mechanical air filters remove particles by capturing them on filter materials. High efficiency particulate air (HEPA) filters are in this category. Electronic air cleaners such as electrostatic precipitators use a process called electrostatic attraction to trap charged particles. They draw air through an ionization section where particles obtain an electrical charge. The charged particles then accumulate on a series of flat plates called a collector that is oppositely charged. Ion generators, or ionizers, disperse charged ions into the air, similar to the electronic air cleaners but without a collector. These ions attach to airborne particles, giving them a charge so that they attach to nearby surfaces such as walls or furniture, or attach to one another and settle faster.

Air cleaning devices can help to improve indoor environment

Indoor air pollution is among the top five environmental health risks. The best way to address this risk is to control or eliminate the sources of pollutants, and to ventilate a home with clean outdoor air. The ventilation method may, however, be limited by weather conditions or undesirable levels of contaminants in outdoor air. If these measures are insufficient, an air cleaning device may be useful. While air cleaning devices may help to control the levels of airborne allergens, particles, or, in some cases, gaseous pollutants in a home, they may not decrease adverse health effects from indoor air pollutants.

(Reference:http://www.epa.gov/iaq/pubs/airclean.html)