We spend 90 percent of our time inside, so it’s smart to think about the air in our homes, especially since it’s often more polluted than the air outside, according to the Centers for Disease Control and Prevention (CDC). But how can you know how clean or dirty your air is? Is an air testing kit the answer?

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Elliot Horner, PhD, lead scientist for UL Environment, has two words for anyone thinking about buying a do-it-yourself test kit or hiring an inspector to take air samples: “Buyer beware.”

The main problem with testing kits, says Horner, is they often check for just one kind of pollutant (though some test for two or more). One kit might test only for formaldehyde, for instance, while another looks only for mold, radon, mouse allergens, dust or some other substance.

This means you’d almost have to know what’s polluting your air before choosing a kit — so what’s the point? “Often, money is better spent addressing the problem rather than testing for it,” says Horner.

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It's also hard to know if a kit will yield accurate results. “I do not know of any way to evaluate one that would be available to the general public,” says Horner.

Take mold, for instance. Testing for it in the air is a difficult process that requires taking 20 or 30 samples. Results can be unreliable, according to Horner. “It's more practical to search for mold with a good nose and strong flashlight,” he says.

Even if the results do identify pollutants in the air, it's “almost impossible” to know whether or not they are making you sick, according to the Consumer Product Safety Commission (CPSC). Some people are very sensitive to small amounts of a certain pollutant, while others aren't bothered even by larger amounts. If you have more than one pollutant in your air, it can be difficult to tell which one is causing your health problems, the CPSC says.

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If you want a professional to test the air in your home, find someone who is experienced with a variety of pollutants, advises Horner. This is especially important if you don't know what kind of pollutants they should be looking for.

“Stay away from the folks who do just one type of problem, such as mold or radon,” he says. “You want someone with an open mind.”

The Indoor Air Quality Association maintains a searchable database of air testing professionals.

Also be wary of products that claim to provide easy solutions to your home's air quality problems. Horner recalls the day he ran across a booth at a trade show, “selling some magic juice that will fix your mold without taking anything apart,” he says. “I threw the brochure away.”

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David Arv Bragi is a freelance journalist and marketing consultant. He has been writing about health and safety issues since the 1990s and currently lives in Portland, Oregon.