Portable air cleaners are popular -- but do they work?

For 50 years, California residents have been fighting to improve the quality of the air outdoors. Now the air-quality battle is shifting indoors, and a new weapon has joined the fray -- portable air cleaners.

Some of these devices use mechanical barriers to filter the air; others create an electrical field to remove pollutants from the air. Sales of these devices have soared in recent years, with Americans buying approximately 3.4 million in 2002.

Health concerns are driving sales. The air inside homes and buildings is often more polluted than that outside. Levels of chemicals such as formaldehyde, for example, are typically many times higher indoors. And contaminants such as tobacco smoke and radon -- present only in very low concentrations outdoors -- can reach potentially dangerous levels indoors.

It’s not just the quality of indoor air that’s worrisome, but the amount of time people are exposed to it. According to the Air Resources Board, Californians spend an average of 87% of their day inside.

Of course, inhaling pollutants isn’t good for your health. Exposure to secondhand smoke, radon or asbestos increases the risk of some cancers -- especially lung cancer. Formaldehyde can cause headaches and burning sensations in the eyes, nose and throat, and molds and pollen can set off allergic reactions.

“My husband and I both have allergies,” says Los Angeles resident Tamara Nichols, who bought an air cleaner a year and a half ago. “I thought it might improve the air quality in our bedroom.”

Unfortunately, many air cleaners don’t dramatically change the air quality. Even those that do remove pollutants haven’t been shown to produce significant health benefits.

If there’s one thing air cleaners are good at, it’s clearing the air of solid particles, such as smoke and dust. Very small particles can be inhaled deep into the lungs and damage the airways. “High-efficiency particulate air filters -- or HEPA filters -- are designed to capture fine particulates,” says Hamid Arabzadeh, an industrial hygienist in Irvine.

However, not all air cleaners contain this type of filter, and not even the best air cleaner can completely remove all particles from room air. Nor can they clear pollutants that aren’t airborne, such as large pollen and mold particles that tend to quickly settle onto the floor and furnishings. (Simply walking through a room or sitting on furniture can stir up these pollutants.)

Further, the mechanical filters and electronic technologies used to capture particulates don’t work well against gases, such as formaldehyde and ammonia. “When you get to chemicals, all bets are off,” Arabzadeh says. “To get rid of chemicals, you need a second layer of protection.”

Although some specially equipped cleaners can trap certain gaseous pollutants, most are not effective against all gases typically present in indoor air. A filter that works against one type of gas might not help with another. Also, chemical filters may eventually release the gases they do trap back into the air.

In short, most consumers won’t get any significant health benefits from air cleaners. People with asthma or allergies are the one possible exception. While several studies have found air cleaners to have little or no effect on asthma and allergy symptoms, others have suggested they might help.

Before investing in a portable air cleaner, try eliminating the sources of indoor air pollution. If tobacco smoke is the problem, don’t allow smoking in the house. If you’re struggling with allergies to a cat or dog, keep the animal outdoors. Also, simply opening doors and windows will increase ventilation and can dramatically improve air quality.

Although flicking a switch on an air cleaner may seem simpler, it may not be more effective. It’s even less effective if you don’t bother to turn the device on. Nichols has only used her unit about four times. “Ironically, it sits collecting dust,” she says with a laugh.

*

(BEGIN TEXT OF INFOBOX)

Filtering the claims

Air cleaners vary widely in their design and effectiveness, and it’s often difficult to determine how well a particular product works. Although there are no industry-wide performance standards used to rate these devices, the Assn. of Home Appliance Manufacturers (AHAM) offers a voluntary certification program.

Products participating in the program undergo testing and display a rating referred to as the clean air delivery rate (CADR). The CADR indicates the cleaner’s ability to clear three particulate pollutants -- tobacco smoke, dust and pollen -- from indoor air; the higher the CADR, the more effective the unit.

*

Dr. Valerie Ulene is a board-certified specialist in preventive medicine practicing in Los Angeles. She can be reached at themd@att.net. The M.D. appears the first Monday of the month.