Portable Air Cleaners
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 when continuous and localized air cleaning is needed. They may be an option if a home is not equipped with a central HVAC system or forced air heating system. 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. For example, if 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.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 http://www.cadr.org.
Will Air Cleaning Reduce Adverse Health Effects?
The ability to remove particles, including microorganisms, is not, in itself, an indication of the ability of an air cleaning device to reduce adverse health effects from indoor pollutants. The use of air cleaning devices may help to reduce levels of smaller airborne allergens or particles. However, air cleaners may not reduce adverse health effects in sensitive population such as children, the elderly, and people with asthma and allergies. For example, the evidence is weak that air cleaning devices are effective in reducing asthma symptoms associated with small particles that remain in the air, such as those from some airborne cat dander and dust mite allergens. Larger particles, which may contain allergens, settle rapidly before they can be removed by filtration, so effective allergen control measures require washing sheets weekly, frequent vacuuming of carpets and furniture, and dusting and cleaning of hard surfaces. (For more on allergen control, visit http://www.epa.gov/asthma.) There are no studies to date linking gas-phase filtration, UVGI, and PCO systems in homes to reduced health symptoms in sensitive populations.
Guide to Air Cleaners in the Home Additional Factors to Consider When making decisions about using air cleaning devices, consumers should also consider:
- Installation: In-duct air cleaning devices have certain installation requirements that must be met, such as sufficient access for inspection during use, repairs, or maintenance.
- Major Costs: These include the initial purchase, maintenance (such as cleaning or replacing filters and parts), and operation (such as electricity).
- Odors: Air cleaning devices designed for particle removal are incapable of controlling gases and some odors. The odor and many of the carcinogenic gas-phase pollutants from tobacco smoke will still remain.
- Soiling of Walls and Other Surfaces: Ion generators generally are not designed to remove the charged particles that they generate from the air. These particles may deposit on room surfaces, soiling walls and other surfaces.
- Noise: Noise may be a problem with portable air cleaners containing a fan. Portable air cleaners without a fan are typically much less effective than units with a fan.
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.