Testing for radon can be done with a do-it-yourself home test. Use only home tests that are labeled "meets EPA requirements." The two types of home tests used to detect radon are short-term and long-term.

You can purchase an EPA-qualified short-term or long-term detector test kit at hardware or retail stores or through government agencies in the United States, including:

• Your regional U.S. Environmental Protection Agency (find your regional office by going to the EPA Web site www.epa.gov/iaq/whereyoulive.html) or by calling the EPA National Radon Hotline at 1-800-SOS-RADON (1-800-767-7236).
• The Consumer Federation of America Foundation's Radon FIX-IT Program hot line at 1-800-644-6999.

If you don't want to do the test yourself or if you are buying or selling a home, you can hire a qualified tester to do the testing for you. Contact your state radon office for a list of qualified testers.

• The short-term test kit stays in your home or office for 2 to 90 days. Radon levels vary daily and from season to season. Therefore, you may want to follow up the first short-term test with a second to determine whether reduction in radon is needed.
• The long-term test kit stays in the home or office for more than 90 days. A long-term test will give more accurate results because radon levels can fluctuate from season to season.

These tests work by measuring average indoor levels of radon in your home or office. Radon is measured in units of radioactivity per volume of air. The most common measure is picocuries per liter of air (pCi/L). The average indoor level of radon is estimated to be about 1.25–1.3 pCi/L, while the average outdoor level of radon is about 0.4 pCi/L.² Levels that equal or exceed 4 pCi/L should be reduced. But the EPA says there is no safe level of radon. Radon levels between 2 pCi/L and 4 pCi/L can be reduced as well. Removing radon sources or venting radon should be done by a contractor specifically trained and certified to fix radon problems.