They normally only give a single average radon level which does not tell you how the radon level in your home varies with time, nor whether or not the test conditions have been interfered with. It comes from the natural breakdown of uranium in soil, rock and water and gets into the air you breathe. Radon typically moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Your home can trap radon inside. Sometimes radon enters the home through well water.
Any home can have a radon problem.
This means new and old homes, well-sealed and drafty homes, and homes with or without basements. In fact, you and your family are most likely to get your greatest radiation exposure at home. That is where you spend most of your time. Nearly 1 out of every 15 homes in the U.S. is estimated to have elevated radon levels. You cannot see radon.