If you have a lung condition and are trying to reduce indoor air pollution in your home, portable air cleaning devices may look like an attractive option to cut down on lung irritants. But do they really work? Here's a review of your choices from the experts at Johns Hopkins.

Air cleaning devices alone won’t remove all indoor pollution from your home. Most will remove some particles from indoor air but not certain types of pollution, including lead dust as well as allergens from pets, dust mites, mold, and roaches. Only a few models remove odors and gases, such as carbon monoxide and radon.

Air cleaning devices are available as portable, stand-alone appliances or as part of a central air system. Smaller portable units usually cost between $50 and $200, while larger or more high-end portable models can cost upwards of $300. The price of a central air cleaner can range from about $1,000–3,000.

Getting the Most From a Portable Air Cleaner
If purchasing a central air cleaner for your home is not in your budget, buying a portable air cleaner can be a good choice. When deciding which portable air cleaner to buy, be sure to:

• Check the air cleaner’s clean air delivery rate (CADR) and room size rating (in square feet of floor area). Portable air cleaners are often rated in terms of their CADR, which is a measure of the rate at which contaminants are removed from the air -- the higher the CADR, the better. Air cleaners have separate CADR ratings for their ability to remove dust, pollen, and environmental tobacco smoke.

  Most manufacturers indicate the room size (in square feet) that is effectively treated by their air cleaner, based on the CADR testing for removal of tobacco smoke, street dust, and common indoor allergens. For example, a CADR of 50 is appropriate for an 80-square-foot room, while a CADR of 200 is a better choice for a room of 320 square feet.

Air Cleaners To Avoid
Some types of air cleaners have been shown to be of no benefit at best -- and at worst, harmful.

• Ozone generators. The U.S. Environmental Protection Agency, the American Lung Association, and other government agencies and health groups advise against using so-called “air purifiers” that are specifically designed to generate ozone indoors.

  Ozone generators are often advertised as emitting “trivalent” oxygen, “activated” oxygen, “allotropic” oxygen, “saturated” oxygen, “superoxygen,” or “mountain-fresh air.” An ozone generator may also be combined with an ionizer. Breathing ozone can be dangerous, especially for the elderly, children, and people with asthma, emphysema, bronchitis, or other respiratory diseases. Long-term exposure to ozone may permanently harm a person’s ability to breathe. The EPA has found that these devices do not effectively destroy microbes, remove odor sources, or reduce indoor pollutants enough to provide any health benefits.

• Ductless range hoods. Air filters in kitchen range hoods that exhaust air into the house (ductless hoods) can trap grease from cooking. However, they don’t effectively remove the air pollutants and moisture produced by cooking or by cooking appliances that burn natural or propane gas. Only ducted hoods that exhaust to the outdoors should be used.
• Desktop air cleaners. Research shows that small, desktop air cleaners have little effect on indoor pollution.
• Houseplants. Although they make lovely decorations, houseplants don’t effectively remove indoor air pollution. It would take a tremendous number of houseplants to produce even a small beneficial effect on indoor air pollution. And that many plants could lead to other indoor pollution problems such as too much moisture.

Bottom Line: In general, it’s not possible to make a definitive statement about the health benefits of air cleaning devices based on the limited scientific evidence that is currently available. One thing that is clear, however: You should not use an air cleaner that deliberately produces ozone.