The Facts on Air Cleaners

Pollutants that can affect the air quality in a home fall into the following two categories:

Particulate matter which includes dust, smoke, pollen, animal dander, tobacco smoke, particles generated from combustion appliances such as cooking stoves, and particles associated with tiny organisms such as dust mites, molds, bacteria, and viruses.

Gaseous pollutants come from combustion processes. Sources include gas cooking stoves, vehicle exhaust, and tobacco smoke. They also come from building materials, furnishings, and the use of products such as adhesives, paints, varnishes, cleaning products, and pesticides.

There are two types of air cleaning devices that remove particles from the air.

Mechanical air filter removes particles from the air by trapping them in a filter. These filters require routine replacement.

Electronic air cleaners such as electrostatic precipitators use 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. This type of air cleaner requires routine cleaning of the flat plates.

Portable air cleaners generally contain a fan to circulate the air and use one or more of the air cleaning devices discussed above. Portable air cleaners may be moved from room to room and used whenever localized air cleaning is needed.

As sited by the EPA, portable air cleaners can be evaluated by their effectiveness in reducing airborne pollutants. This effectiveness is measured by the clean air delivery rate (CADR) developed by the Association of Home Appliance Manufacturers (AHAM). The CADR is a measure of a portable air cleaner's delivery of contaminant-free air, expressed in cubic feet per minute. If for example an air cleaner has a CADR of 250 for dust particles, it may reduce dust particle levels to the same concentration as would be achieved by adding 250 cubic feet of clean air each minute. While a portable air cleaner may not achieve its rated CADR under all circumstances, the CADR value does allow comparison across different portable air cleaners.

Also sited by the EPA, many of the portable air cleaners tested by AHAM have moderate to large CADR ratings for small particles. However, for typical room sizes, most portable air cleaners currently on the market do not have high enough CADR values to effectively remove large particles such as pollen, dust mite, and cockroach allergens. Some portable air cleaners using electronic air cleaners might produce ozone, which is a lung irritant. AHAM has a portable air cleaner certification program, and provides a complete listing of all certified cleaners with their CADR values on its Web site at www.cadr.org.