Radon: the invisible gas in your home

Radon is a radioactive gas you can't see or smell, and it's the leading cause of lung cancer among people who don't smoke. The EPA predicts radon potential for every US county - but the only way to know your home's level is to test it.

Quick Answers

What is radon? A radioactive gas from the natural breakdown of uranium in soil that seeps into homes and collects on lower floors. The EPA action level is 4 pCi/L.

How do I check my area? Enter your ZIP code on the KnowYourExposure homepage to see your county's EPA radon zone alongside your water report.

The EPA radon zones

Zone 1 (highest potential): predicted average at or above the EPA action level of 4 pCi/L - every home should be tested. Zone 2 (moderate): 2 to 4 pCi/L. Zone 3 (low): below 2 pCi/L.

Zones are the EPA's predicted county averages (Map of Radon Zones, EPA 402/A-16/001) - a screening tool, not a measurement of any individual home.

How to test your home

A short-term test kit (2 to 7 days) or a continuous digital radon monitor both work; place it in the lowest lived-in level of your home. If a short-term test reads 4 pCi/L or higher, confirm with a second test, then contact a certified radon mitigation contractor.