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 to the air above and into your home through cracks and other holes in the foundation. Your home traps radon inside, where it can build up. Any home may have a radon problem. This means new and old homes, well-sealed and drafty homes, and homes with or without basements. Radon can enter the home through cracks in solid floors, walls, construction joints, gaps in suspended floors and around service pipes, wall cavities and the well water supply.

The two main methods used for radon testing involves the use of a "passive" device such as an activated charcoal test kit which collects radon gas atoms for counting in a laboratory, or an alpha track device which uses a small strip of special plastic that is marked when hit by radon's alpha particles. The other main method is the use of an "active" device called a CRM (continuous radon monitor). The latter is for short term testing, usually 2 days, during real estate transactions or other reasons for the need for immediate results. The main purpose of the passive method testing is for a radon "screening measurement" to determine if there is a potential radon problem in the home and the need for additional long term testing.