It's easy to tell when laundry is clean, or when your floor is clean. But how can you tell when the air in your home is clean? It's a common concern, and rightly so: the U.S. Environmental Protection Agency (EPA) ranks indoor air pollution as one of the top five environmental risks to public health. While outdoor pollution, building materials, and household chemicals carry much of the blame, not all pollutants come from the chem lab.
Dust mites, pollen, soot from candles and fireplaces, and dirt tracked in on shoes are potential irritants, too. But there's a simple way to reduce the amount of pollutants we breathe: Filter your indoor air.
"Central air or heating systems with HEPA filters and air purifiers with HEPA or carbon filters can really upgrade your health," says Katharine Woessner, M.D., program director of the Allergy, Asthma, and Immunology Division of Scripps Clinic in La Jolla, California. Since the quality of an air purifier can be less than crystal clear, we offer the following guide for evaluating units. Keep in mind that while many filters clean the air effectively, they can't replace regular, thorough cleaning and home maintenance.
If your house is alive with dust mites or mold spores, even the most powerful system may fail to eliminate problems. Proper ventilation, frequent washing of drapes and linens, dusting, and vacuuming address those problems at the source, as will the removal of any source of mold or mildew.
Comparing air purifiers
Grade an air cleaner on two counts: the size of microscopic particles that it can remove, and the amount of air it draws through. Particles are measured in microns: pollen grains are 10 to 100 microns and dust-mite debris particles run 0.5 to 50 microns.
In most cases, very small particles are more likely to penetrate deep into lungs and cause health problems. Larger particles may not reach the lungs but may trigger allergies. The most effective purifiers currently on the market can remove particles down to 0.3 microns in size.
The EPA and the American Lung Association cite CADR, or "clean air delivery rate," as the gold standard of air-cleaner effectiveness. It measures the volume of air cleaned within a certain time -- the higher the CADR, the more effective the filter.
When shopping, look for the Association of Home Appliance Manufacturers' (AHAM) seal of approval, usually found on the back of the box. The seal will list three CADR numbers: one for tobacco smoke, one for pollen, and one for dust. The AHAM advises selecting a unit with a tobacco smoke CADR that's at least two-thirds your room's square footage.
For example, a 10 x 12-foot room (120 square feet) would require an air cleaner with a tobacco smoke CADR of at least 80. The same formula applies to dust and pollen. In smaller rooms, the unit will simply clean the air faster. If you have ceilings higher than eight feet, get an air cleaner rated for a larger room to account for the increased volume.
Zany air cleaning devices use two or more filtering technologies to deliver results, and all require cleaning and maintenance for optimal operation.
Be wary of ozone filters and ion exchange (or ionization) units. The former produce the known irritant ozone, which, among other things, can interact with formaldehyde-impregnated particleboard and create a chemical that's damaging to nasal and bronchial airways, Woessner says. Theresa Dale, N.D., Ph.D., founder and dean of the California College of Natural Medicine in Santa Cruz, California, concurs: "Continually inhaling ozone jeopardizes your immune system." The California EPA has issued similar warnings.
Ion exchange units have also come under scrutiny. Research published in Consumer Reports in May 2005 found that five of the six ionizing cleaners tested, including The Sharper Image's Ionic Breeze Quadra Silent Air Purifier, were ineffective in removing pollen, dust, and smoke from air. To find a filter that's safe and effective, consider the following types.
Many consider these filters the best option for living spaces. They use a labyrinth of fibers to trap more than 99 percent of all particles down to 0.3 microns in size, including asbestos, dust, pollen, mold, animal dander, tobacco smoke, and bacteria. If you're allergic to dust mites, a vacuum with a HEPA (High Efficiency Particulate Air) filter can help, since it traps mites and their waste. HEPA filters have been deemed effective by the American Medical Association, the American Lung Association, and the American Academy of Allergy, Asthma and Immunology. AHAM-certified brands with HEPA filters include Blueair, Bionaire, Honeywell, and Kenmore.
Bedrooms, living rooms, offices, and other small living areas. Vacuums that incorporate HEPA filters are helpful in spaces of any size.
HEPA filters are simple to maintain. Some remove easily for washing, while others need replacement every six months to five years.
HEPA filters can't handle large enough volumes of air to make them suitable for central heating or air-conditioning systems.
Carbon filters trap pollutants in microscopic cavities. (The sheets of carbon are steam treated to increase the number of pits.) Carbon filters often team up inside a unit with another purification system. AHAM-certified brands include Honeywell, Kenmore, and LifeWise.
Urban and industrial areas, as they trap ozone, gaseous pollutants such as dry-cleaning solvents, volatile organic compounds, odors, pesticides, and numerous organic chemicals.
Most carbon filters require frequent changing, usually once a month.
If maintenance isn't your thing, activated carbon filters may be incompatible with your lifestyle.
These filters use an electric charge to attract and capture particulate matter, including molds, pollens, bacteria, asbestos, airborne animal dander, and tobacco smoke. You'll find electrostatic filters in AHAM-certified Friedrich and Blueair air purifiers.
Furnaces and central air-conditioning systems, in which they're often used as a pre-filter.
It's important to clean electrostatic filters frequently, since they're less effective when covered in dust. Some manufacturers recommend monthly cleaning.
Electrostatic filters won't remove gaseous pollutants like chemical fumes and odors. As with carbon filters, maintenance is relatively high.
Check out these related Web sites to shop smarter and breathe easier.
For indoor air pollution facts and purification strategies, visit epa.gov/ebtpages/airindoorairpollution.html.
For air pollution and ozone levels anywhere in the United States, check out lungaction.org/reports/stateoftheair2005.html.
HEPA help To find out more about devices with HEPA filters, visit missionallergy.com. Founded by an allergist, this user-friendly site takes a rigorously scientific approach to product recommendations and sells a variety of merchandise.