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Explain Working Levels (WL) and Picocuries Per Liter of Air (pCi/L).

Radon test results may be reported in three different measures – picocuries (pCi/l), Working Levels (WL) and bequerels (bq). If your test result is in pCi/L, EPA recommends you fix your home if the radon level is 4 pCi/L or higher. If the test result is in WL, EPA recommends you fix your home if the working level is 0.016 WL or higher. Some states require WL results to be converted to pCi/L to minimize confusion. While not commonly used in the United States, any radon level at or above 0.148 bq should be reduced.

See our Radon Glossary of Terms  and the CDC/ATSDR’s Toxicological Profile for Radon: Chemical and Physical Information

Find your state radon coordinator at