Radon is a naturally occuring radioactive gas, produced when uranium decays. Trace quantities of uranium are widely present in rocks and soils from which radon is continually produced. In the ground, radon diffuses to the surface. Outdoors it readily disperses and very low quantities of radon are found in outdoor air. In houses, radon can enter from under the floor where it can accumulate. The normal concentration of radon in UK houses is lower than in most other European countries. Some houses, however, can harbour appreciable levels which may be of health concern, especially for the risk of lung cancer.
The variations in radon levels not only differs from place to place but more importantly from house to house, making a radon measurement relevant to any home, workplace or school.