Radon is a radioactive gas. It comes from the natural decay of uranium that is found in nearly all soils. It typically moves up through the ground, then into your home through cracks and other openings in the foundation. Your home traps Radon inside, where Radon levels can build up. Any building has potential for Radon decay products to be present. This means new and old homes, well-sealed and drafty homes, and homes with or without basements.