Q: We are looking for a newer home, and I have a question about radon. We were told we had the right to have the home tested, but I don't know if it's worth the cost. The radon test was not included in the costs from the home inspectors we talked to.

A: Radon is a naturally occurring, radioactive, colorless, odorless gas that comes from the decay of uranium in soils and rocks, and it can sometimes be found in well water. Wherever you live, shop or go to church or school, you are breathing radon gas.

Radon is a known carcinogen and, according to U.S. Environmental Protection Agency estimates, radon is the second-leading cause of lung cancer. (For more information, visit http://www.epa.gov/radon/healthrisks.html). Radon is measured in picocuries per liter of air, represented as ''PCI/L." The average concentration of radon in outdoor air is .4 PCI/L (http://www.epa.gov/radon/aboutus.html).

Because radon gas is the heaviest of the known gases, approximately nine times denser than air, it tends to build up in the lower levels of buildings such as basements or homes with a concrete-slab foundation.

However, even homes with a vented crawlspace can have radon levels that exceed the national standard for mitigation, which is 4.0 PCI/L or 10 times the average outdoor concentration.

When purchasing a home, you do not have the luxury of performing the recommended 60- to 90-day test, which would give you a more accurate picture of the radon levels in the home. Rather, during a home sale the test will be performed over a 48- to 72-hour period, giving you just a snapshot in time of what the radon levels are.

Radon tests can be affected by windy weather or heavy rains, and tampering with the test unit can cause higher-than-expected readings. If the readings are unusual, a second test should be performed. The EPA recommends that every home be tested for radon and by a certified radon inspector. If you decide to purchase the home without a certified test, you can do the test yourself after moving into the home, but you would not be able to negotiate with the seller for the cost of mitigation if the levels were high. Test kits are available at major home and hardware stores or kits can be ordered online.

(Dwight Barnett is a certified master inspector. Contact him at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 268, Evansville, Ind. 47702 or barnett@barnettassociatesinc.com.)

AP-WF-04-15-13 1518GMT