The Louisville Metro Department of Public Health and Wellness is giving away free radon testing kits. Radon is the second leading cause of lung cancer in the U.S., behind smoking.

Radon doesn’t have a smell, and can’t be tasted, and it’s a natural gas that is released when metals break down in rocks, soil and groundwater. About 40 percent of homes in Kentucky are estimated to have unsafe levels. And the only way to know if a home has unsafe levels is to test for radon.

“Radon can exist at dangerous levels in homes in Louisville, but people may not know it because it’s a gas that you can’t smell or see,” said Dr. Sarah Moyer, director of the Louisville Metro Department of Public Health and Wellness, in a release. “We encourage people to take advantage of the free test kits to test their homes for radon.”

People who smoke are also at higher risk of developing lung cancer if they are exposed to radon. Many people who have radon-related lung cancers also have a history of exposure to tobacco smoke; that’s because smoking significantly increases the risk of the cancer from radon. According to the Kentucky Cancer Registry, the rate of lung cancer in Louisville is 94.8 per 100,000 people, compared to 59.4 nationally per 100,000 people nationally.

Experts suggest opening windows and using ceiling fans to circulate indoor air to avoid exposure to radon. You can also seal cracks in floors with plaster and caulk to keep radon from leaking in.

Residents can request a kit by clicking here or by calling 574-6650.