Radon detectors measure levels in picocuries per liter (pCi/L) to indicate the average, year-round radon levels. If your home measures between 2 pCi/L and 4 pCi/L, consider taking steps to reduce radon levels. Any result above 4pCi/L should be confirmed with a follow-up test. If the result remains high, take immediate action to reduce the radon levels in your home.