Updated November 2026 · Data: EPA Map of Radon Zones · Sources
No Arizona counties are in EPA Zone 1, but 15 of 15 are in Zone 2, where the predicted average indoor radon level is between 2 and 4 pCi/L. Find your county below, then learn how to test your home and what to do if the result is high.
Your county’s zone is not your home’s radon level. Homes with high radon are found in every zone. The EPA recommends testing every home, whatever its zone.
Map of EPA radon zones by county
Radon zones by county in Arizona
The table lists the EPA radon zone for each of the 15 counties in Arizona. The zone shows the predicted average indoor radon screening level for homes in that county.
| County | EPA zone | Predicted average indoor level |
|---|---|---|
| Apache | Zone 2 | 2 to 4 pCi/L |
| Cochise | Zone 2 | 2 to 4 pCi/L |
| Coconino | Zone 2 | 2 to 4 pCi/L |
| Gila | Zone 2 | 2 to 4 pCi/L |
| Graham | Zone 2 | 2 to 4 pCi/L |
| Greenlee | Zone 2 | 2 to 4 pCi/L |
| La Paz | Zone 2 | 2 to 4 pCi/L |
| Maricopa | Zone 2 | 2 to 4 pCi/L |
| Mohave | Zone 2 | 2 to 4 pCi/L |
| Navajo | Zone 2 | 2 to 4 pCi/L |
| Pima | Zone 2 | 2 to 4 pCi/L |
| Pinal | Zone 2 | 2 to 4 pCi/L |
| Santa Cruz | Zone 2 | 2 to 4 pCi/L |
| Yavapai | Zone 2 | 2 to 4 pCi/L |
| Yuma | Zone 2 | 2 to 4 pCi/L |
What the EPA radon zones mean
- Zone 1 (highest potential): predicted average indoor screening level greater than 4 pCi/L. In Arizona: 0 counties (0%).
- Zone 2 (moderate potential): predicted average between 2 and 4 pCi/L. In Arizona: 15 counties (100%).
- Zone 3 (low potential): predicted average below 2 pCi/L. In Arizona: 0 counties (0%).
The EPA built the map from indoor radon measurements, geology, soil permeability and type of house foundation. It was made to help governments and builders target resources, not to decide whether a single home needs testing.
How to test for radon in Arizona
Testing is the only way to know your home’s radon level. Short-term test kits (2 to 90 days) are sold at hardware stores and online, and some state programs offer kits at low cost; check with the Arizona Department of Health Services, Bureau of Radiation Control. Test in the lowest lived-in level of the home, with windows and doors closed, and follow the kit instructions.
- Do-it-yourself kits: a simple, low-cost first step for your own home.
- Long-term tests (more than 90 days): give a better picture of your home’s year-round average.
- Certified professionals: look for certification from the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB), and ask the state program whether Arizona requires a state license.
- Buying or selling a home: ask for a radon test as part of the home inspection.
The Arizona radon program has provided free radon test kits to homeowners; check the program website for current availability.
If your radon level is high
The EPA recommends fixing your home if the radon level is 4 pCi/L or higher, and considering a fix between 2 and 4 pCi/L. The most common fix is a radon mitigation system (sub-slab depressurization), which pulls radon from under the foundation and vents it outside, above the roof line.
- The EPA says most homes can be fixed for about the same cost as other common home repairs; the price depends on the size and design of the home.
- Get estimates from more than one qualified, certified mitigation contractor. See our radon mitigation cost guide for typical prices.
- Test again after the system is installed, and retest every few years.
Learn more: safe radon levels · how to test · test kits compared · radon and home sales · radon in well water
Arizona radon program
Radon rules and programs in Arizona
- Home sales: Arizona law requires sellers to disclose material facts about the property, and the standard seller disclosure form asks about radon.
Contact
The Arizona Department of Health Services, Bureau of Radiation Control answers questions from residents about radon testing, results and certified professionals.
- Phone: 602-255-4845 ext. 6
- Website: azdhs.gov/licensing/radiation-regulatory/index.php#radon-home
Contact details as listed by the state radon program directory. Please confirm on the program’s website before calling.
Frequently asked questions
Is radon a problem in Arizona?
None of Arizona’s 15 counties are in EPA Zone 1, but high radon levels can be found in any home, in any zone. Testing is the only way to know your level.
Do I need to test if my county is in Zone 2 or 3?
Yes. The EPA zones show predicted averages for large areas, and they were not designed to decide whether a single home needs testing. The EPA recommends testing every home.
What radon level is safe?
There is no known safe level of radon. The EPA recommends fixing your home at 4 pCi/L or higher and considering a fix between 2 and 4 pCi/L.
Who can I contact about radon in Arizona?
The Arizona Department of Health Services, Bureau of Radiation Control answers questions about testing, results and certified professionals. Phone: 602-255-4845 ext. 6.
Sources
- SOSRadon.org (CRCPD/EPA): Arizona state radon program fact sheet (2022)
- U.S. EPA: EPA Map of Radon Zones (county data file, June 2024)
- U.S. EPA: A Citizen’s Guide to Radon (checked November 2026)
- U.S. EPA: How much can a radon mitigation system cost? (updated September 16, 2026)
- Arizona Department of Health Services, Bureau of Radiation Control (checked November 2026)
- SOSRadon.org (CRCPD): State radon contacts (checked November 2026)