The U.S. Environmental Protection Agency recommends a tested radon level of less than 4 picocuries per liter of volume in homes. Levels of 4 picocuries per liter or above should prompt the installation of a radon mitigation system.
Radon, a radioactive gas, enters homes through cracks, joints, gaps, cavities and water supplies. Breathing radioactive particles can cause lung cancer. Any amount of radon can result in negative health consequences, so positive detection of radon is advised. Mitigation involves pumping out subterranean areas beneath the house with a vent pipe and fan. Proper mitigation procedures can reduce radon levels to less than 2 picocuries per liter.