Is radon high in Arizona?

Arizona's population-weighted predicted basement average is 1.7 pCi/L, close to the US average of 1.8. 0 of its 15 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 6 are in the 2-4 "consider fixing" range and 9 are below 2. 0% of Arizona ZIP codes are predicted at 4 or higher.

Which Arizona county has the highest radon?

Coconino County has the highest predicted basement average in Arizona at 2.3 pCi/L (EPA Zone 2). The lowest is Yuma County at 1.5 pCi/L. These are modeled area averages; individual homes in any county can test far higher.

How many EPA Zone 1 counties are in Arizona?

0 of Arizona's 15 counties (0%) are EPA Zone 1 (highest potential), 15 are Zone 2 and 0 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.

Should I test for radon in Arizona?

Yes. Even though Arizona's predicted average is below 2 pCi/L, the EPA recommends every home be tested - radon varies house to house, and 26.9% of Arizona ZIP codes are still predicted at 2 pCi/L or higher.

Radon levels in Arizona: Low

The model predicts a population-weighted basement average of 1.7 pCi/L across Arizona's 15 counties - close to the US average of 1.8 pCi/L. Above-ground floors average 1.0 pCi/L.

Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.

0 / 15

EPA Zone 1 counties (0%)

15 / 0

Zone 2 / Zone 3 counties

counties predicted ≥ 4 pCi/L

of ZIP codes predicted ≥ 4 pCi/L

Arizona counties by predicted radon

Sorted highest to lowest predicted basement average. 15 counties.

County	Predicted basement	Upstairs	Grade	EPA zone	ZIPs
Coconino County	2.3 pCi/L	1.8	Moderate	EPA Zone 2	17
Navajo County	2.3 pCi/L	1.4	Moderate	EPA Zone 2	17
Gila County	2.3 pCi/L	1.5	Moderate	EPA Zone 2	8
Graham County	2.2 pCi/L	1.3	Moderate	EPA Zone 2	6
Apache County	2.1 pCi/L	1.2	Moderate	EPA Zone 2	14
Yavapai County	2.1 pCi/L	1.4	Moderate	EPA Zone 2	25
Greenlee County	2.0 pCi/L	1.2	Low	EPA Zone 2	4
Santa Cruz County	2.0 pCi/L	1.1	Low	EPA Zone 2	7
Cochise County	1.9 pCi/L	1.0	Low	EPA Zone 2	16
Pinal County	1.7 pCi/L	0.9	Low	EPA Zone 2	25
Pima County	1.7 pCi/L	0.8	Low	EPA Zone 2	40
Mohave County	1.7 pCi/L	0.9	Low	EPA Zone 2	18
Maricopa County	1.7 pCi/L	0.9	Low	EPA Zone 2	129
La Paz County	1.7 pCi/L	0.8	Low	EPA Zone 2	5
Yuma County	1.5 pCi/L	0.8	Low	EPA Zone 2	7

Arizona radon questions

Is radon high in Arizona?: Arizona's population-weighted predicted basement average is 1.7 pCi/L, close to the US average of 1.8. 0 of its 15 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 6 are in the 2-4 "consider fixing" range and 9 are below 2. 0% of Arizona ZIP codes are predicted at 4 or higher.
Which Arizona county has the highest radon?: Coconino County has the highest predicted basement average in Arizona at 2.3 pCi/L (EPA Zone 2). The lowest is Yuma County at 1.5 pCi/L. These are modeled area averages; individual homes in any county can test far higher.
How many EPA Zone 1 counties are in Arizona?: 0 of Arizona's 15 counties (0%) are EPA Zone 1 (highest potential), 15 are Zone 2 and 0 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
Should I test for radon in Arizona?: Yes. Even though Arizona's predicted average is below 2 pCi/L, the EPA recommends every home be tested - radon varies house to house, and 26.9% of Arizona ZIP codes are still predicted at 2 pCi/L or higher.

Arizona radon program

Many states offer free or discounted test kits and keep lists of certified mitigators. Find the Arizona radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.