MADISON, Wis. -

Public Health of Madison and Dane County are warning residents of the dangers of letting homes turn into radon traps during National Radon Action Month.

When houses are closed up to keep in the heat, radon gas seeping into homes has nowhere to go and radon levels ca increase, officials said.

Much of Dane County land has small amounts of uranium in the soil, and uranium breaks down to produce radon gas and other byproducts, according to a release. Radon gas can move up through cracks and holes in a building’s foundation and enter homes.

According to the release, about 46 percent of homes tested in Dane County in 2012 had levels of radon that are considered unsafe. Radon gas is odorless, invisible and tasteless, and can damage your lungs and put families at risk for lung cancer.

Public Health offers a simple, inexpensive way to detect the presence of radon gas, according to the release. Radon testing kits are available for $10.

If tests reveal your home has elevated radon levels, officials recommend installing a system that will prevent radon from entering your home. Systems should be installed by a certified mitigation contractor.

“While the cost of fixing this problem can seem high (typically $800 to $1,200), it is a real bargain when weighed against removing the threat of lung cancer from your home,” Public Health radon specialist Janice Block Banks said in the release.

The Environmental Protection Agency estimates that radon is responsible for 21,000 lung cancer deaths every year in the United States, according to the release. About 2,900 of those deaths occur among people who never smoked.