An air purifier is a necessity for those who suffer from allergies or asthma. Considering the levels of pollution these days--including indoor pollution--it would certainly be helpful for everyone to breathe cleaner air. Your primary decision when purchasing an air purifier is the type of filter or purification technology.The most common type of filter is the HEPA (High Efficiency Particulate Arresting) filter. The HEPA filter material is densely folded to create the maximum surface area. It is claimed that a HEPA filter will remove up to 99.97 percent of bacteria, animal hair and dander, pollen, mold spores, dust and dust mites, smoke particles and other particulate allergens. Bacteria, dust mites and other living organisms will die in the filter from lack of water. Carbon filters are often used in conjunction with HEPA filters to remove gaseous pollutants and odors. The filters must be changed when full, and only the air that actually circulates through the filter gets cleaned.
Ionizers do not use filters. Most of the harmful or irritating pollutants in indoor air, such as viruses, bacteria and odors, carry a positive electron charge. Ionizers release large amounts of negative ions into the air to neutralize those pollutants. However, you should be certain that your ionizer can circulate the appropriate amount of ions for the size of the room.
A third type of air purifier uses ultraviolet light, which has germicidal properties. Since UV light doesn't affect non-living particles or gases, these purifiers are often combined with HEPA filters and/or ionizers for complete air purification. You should also note that the EPA has stated that ozone generators, which enjoyed brief popularity, are not effective air purifiers, and in fact may increase the level of contaminants.