Disclaimer

Last updated: September 2026

Informational only

RadonGrade is an informational website. Nothing on it is medical, legal, engineering or real-estate advice, and nothing on it creates a professional relationship of any kind. Decisions about testing, mitigation, health or a property transaction should be made with qualified professionals and, where relevant, your state radon program.

Predicted values are modeled estimates, not measurements

The radon levels shown for ZIP codes, counties, states and the nation are predictions from a statistical model (the National Radon Exposure Model) of the long-term average for an area. They are not measurements taken in any home, including yours. Radon in an individual house depends on the soil directly beneath it, how the foundation was built, and how the home is heated and ventilated; neighboring homes routinely differ by several times. A "Low" grade does not mean your home is safe, and a "High" grade does not mean your home has a problem.

Not a substitute for testing

The only way to know the radon level in a specific building is to test it. The EPA recommends that every home below the third floor be tested regardless of location. This site exists to tell you how urgent that test is, not to replace it. See how to test for radon.

EPA zones

EPA radon zones are a 1993 county-level classification intended to help governments target resources. The EPA states that the map should not be used to determine whether a home should be tested, and that homes with elevated radon exist in all three zones.

Accuracy and third-party data

We reproduce public datasets as faithfully as we can and document every processing step in the methodology, but we make no warranty that any figure is accurate, complete or current. Source datasets have their own limitations and may be revised by their publishers. Cost figures (for example the typical mitigation range) are industry-typical ranges, not quotes.

Affiliate disclosure

RadonGrade participates in the Amazon Services LLC Associates Program and may participate in other affiliate programs (for example manufacturer programs for radon monitors). When you click a link marked as sponsored and make a purchase, we may earn a commission at no additional cost to you. Affiliate relationships do not influence the data, thresholds or grades shown on this site, which follow published EPA guidance. We are not affiliated with the EPA, any state agency, or the authors of the National Radon Exposure Model.

External links

Links to government, academic and commercial sites are provided for convenience. We do not control their content and are not responsible for it.

Limitation of liability

To the fullest extent permitted by law, RadonGrade and its operators are not liable for any loss or damage arising from use of, or reliance on, this site or its content. See also our Terms of Use.