There is no completely safe level of radon exposure; however, the EPA has set an action level of 4 picocuries per liter (pCi/L) of air. At or above this level, it is recommended to take measures to reduce radon levels. Even levels between 2 and 4 pCi/L pose some risk, and lowering radon levels below 2 pCi/L is advisable if feasible.
