Understanding your radon test results
Radon in air is measured in picocuries per liter, written pCi/L.[1] Here's what the Vermont Department of Health says to do at each level.
Radon in air
| Your result | Health Department guidance |
|---|---|
| 4.0 pCi/L or higher | Contact a certified radon mitigation contractor to help reduce radon levels in your home. If your water comes from a well, test your water for radon too.[2] |
| 2.0 to 4.0 pCi/L | Consider mitigation, since radon levels in this range can still pose some risk.[2] |
| Below 2.0 pCi/L | Test your home again in five years.[2] |
The action level of 4.0 pCi/L means that at or above it, the Health Department and EPA recommend reducing radon levels in your home. Because levels below 4.0 still pose some risk, they encourage taking action to lower radon below 2.0 pCi/L.[1]
How your number compares
- Average outdoor air in Vermont: 0.4 pCi/L.[1]
- Average Vermont home: about 2.5 pCi/L.[1]
- Average indoor level nationally: about 1.3 pCi/L, as estimated by the EPA.[3]
Most radon mitigation systems can reduce radon levels in a home to 2.0 pCi/L or lower.[1]
If you used short-term tests
For a real estate test, the EPA says to fix the home if the average of two short-term tests (taken together, or one right after the other) is 4 pCi/L or more, or if the average from a continuous monitor run for at least 48 hours is 4 pCi/L or more. When long-term test results are 4 pCi/L or higher, the EPA recommends fixing the home.[3]
Radon in water
The Health Department has set an advisory level for radon in water of 4,000 pCi/L. To understand your risk, you also need your home's radon in air result; if you haven't tested your air, do that before deciding how to reduce radon.[4]
- At or above 4,000 pCi/L: take action to reduce radon levels in your home. The state's radon contribution calculator can help you work out the best fix.[4][5]
- Below 4,000 pCi/L: you do not need to treat your water. Test again in five years.[4]
More on this in Radon in well water.
What the health agencies say about risk
This site shares official guidance only and isn't medical advice. If you have questions about your health, talk with a health care provider.
- Breathing in radon increases your risk of lung cancer over your lifetime. Your risk depends on the level of radon, how long you're exposed, and whether you smoke.[1]
- Radon is estimated to cause 21,000 lung cancer deaths every year in the United States.[2]
- The EPA estimates that 86% of radon-related lung cancer deaths occur among current or former smokers.[1] For help quitting, the Health Department points to 802Quits.org and 1-800-QUIT-NOW.[6]
- Over a lifetime, drinking water with radon also poses a risk of stomach cancer, but the major danger from radon in water is breathing in the radon released from it.[2]
Sources
- Radon in Your Home, Vermont Department of Health. Checked 2026-10-17.
- Fixing Radon in Your Home (fact sheet, January 2024), Vermont Department of Health. Checked 2026-10-17.
- Home Buyer's and Seller's Guide to Radon (EPA 402/K-24/001, March 2024), U.S. Environmental Protection Agency. Checked 2026-10-17.
- Radon in Drinking Water, Vermont Department of Health. Checked 2026-10-17.
- Radon Contribution Calculator (Excel), Vermont Department of Health. Checked 2026-10-17.
- Tracking Radon in Vermont, Vermont Department of Health. Checked 2026-10-17.