Date Published: 02/19/2007 [Source]
Radon is produced by the decay of uranium minerals found in rock and soil, and concentrations of the gas had been found indoors in some homes, notably in the Northeast. It used to be a problem primarily associated with mines until it was reported being found in homes 20 years ago.
The EPA recommends corrective action in homes with radon levels at or above 4 picocuries per liter of air. Accurate radon testing should be done with a kit that can generate a report from an EPA certified lab.