Radon is a radioactive gas that is released when uranium—a natural element found in rock and soil—breaks down and decays. Radon can leak from the ground into a home or other building through cracks in the foundation or gaps around pipes.

Long-term exposure to radon has been linked to the development of lung cancer.

Radon cannot be detected by human senses because it is odorless, tasteless, and invisible. But levels can be measured in enclosed spaces with home test kits. Radon levels in homes and other buildings can be reduced by methods such as venting the radon out of the soil under the house, moving air through crawl spaces with a fan, and increasing the pressure in basements to prevent radon from seeping in.