The U.S. Environmental Protection Agency (EPA) has named January its National Radon Action Month, and homeowners can participate by hiring an experienced home inspection service that can test for elevated levels of the harmful gas.

Exposure to radon gas contributes to the deaths of 21,000 Americans annually and is the second-leading cause of lung cancer in the United States, following smoking, according to the EPA. The gas, which is emitted when water, soil, rocks and other materials below the earth's surface begin to break down naturally, is odorless and invisible, so homeowners are unlikely to detect it without professional assistance.

"Radon is a dangerous health threat to our families and communities that can be easily avoided through simple testing," EPA administrator Karl Brooks said in a press release. "This month, I urge everyone to test their homes."

Radon is a gas that is found to have enhanced levels in about one out of every 15 American homes. If a home has cracks in its foundation, radon could seep into the home via cracks in the foundation or through pipes, causing harm to those who live there.

The EPA and other experts advise that homeowners test their homes either with a home testing kit or with an experienced home inspection company. Many industry observers advise hiring a professional to complete testing because he or she would have the experience necessary to identify increased levels of the gas,. This service also likely has access to a better radon detector system.

While radon does not cause any immediate health effects, it should still be dealt with as soon as possible. A home inspection service can also provide suggestions on how to deal with the prevalence of radon.