Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock () or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

This is not the current EPA website. To navigate to the current EPA website, please go to www.epa.gov. This website is historical material reflecting the EPA website as it existed on January 19, 2025. This website is no longer updated and links to external websites and some internal pages may not work. More information »

JavaScript appears to be disabled on this computer. Please click here to see any active alerts.

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

Radon test results may be reported in three different measures – picocuries per liter (pCi/L), Working Levels (WL) and becquerels per meter cubed (Bq/m³). If your test result is in pCi/L, the EPA recommends you fix your home if the radon level is 4 pCi/L (150 Bq/m³)or higher. If the test result is in WL, the 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 150 Bq/m³ 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.