Radon levels in Idaho: Moderate
The model predicts a population-weighted basement average of 2.6 pCi/L across Idaho's 44 counties - about 1.4× the US average of 1.8 pCi/L. Above-ground floors average 1.7 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.
19 / 44
EPA Zone 1 counties (43%)
20 / 5
Zone 2 / Zone 3 counties
2
counties predicted ≥ 4 pCi/L
3.3%
of ZIP codes predicted ≥ 4 pCi/L
Idaho counties by predicted radon
Sorted highest to lowest predicted basement average. 44 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Teton County | 4.4 pCi/L | 2.9 | High | EPA Zone 2 | 4 |
| Madison County | 4.3 pCi/L | 2.3 | High | EPA Zone 2 | 4 |
| Jefferson County | 4.0 pCi/L | 2.2 | Moderate | EPA Zone 2 | 7 |
| Custer County | 3.7 pCi/L | 2.3 | Moderate | EPA Zone 1 | 5 |
| Kootenai County | 3.7 pCi/L | 2.5 | Moderate | EPA Zone 1 | 11 |
| Blaine County | 3.6 pCi/L | 3.4 | Moderate | EPA Zone 1 | 5 |
| Bear Lake County | 3.4 pCi/L | 2.3 | Moderate | EPA Zone 2 | 6 |
| Lemhi County | 3.2 pCi/L | 2.4 | Moderate | EPA Zone 1 | 7 |
| Camas County | 3.1 pCi/L | 2.1 | Moderate | EPA Zone 1 | 2 |
| Butte County | 3.1 pCi/L | 1.9 | Moderate | EPA Zone 1 | 3 |
| Bingham County | 3.0 pCi/L | 1.8 | Moderate | EPA Zone 2 | 6 |
| Shoshone County | 3.0 pCi/L | 2.0 | Moderate | EPA Zone 1 | 9 |
| Cassia County | 2.9 pCi/L | 1.7 | Moderate | EPA Zone 2 | 5 |
| Fremont County | 2.9 pCi/L | 2.0 | Moderate | EPA Zone 1 | 3 |
| Caribou County | 2.9 pCi/L | 2.2 | Moderate | EPA Zone 2 | 3 |
| Boise County | 2.9 pCi/L | 1.9 | Moderate | EPA Zone 1 | 6 |
| Elmore County | 2.8 pCi/L | 2.3 | Moderate | EPA Zone 1 | 5 |
| Bonneville County | 2.8 pCi/L | 1.7 | Moderate | EPA Zone 2 | 10 |
| Clark County | 2.8 pCi/L | 1.9 | Moderate | EPA Zone 1 | 2 |
| Oneida County | 2.7 pCi/L | 1.8 | Moderate | EPA Zone 2 | 2 |
| Franklin County | 2.7 pCi/L | 2.0 | Moderate | EPA Zone 2 | 6 |
| Bannock County | 2.6 pCi/L | 1.8 | Moderate | EPA Zone 2 | 7 |
| Power County | 2.6 pCi/L | 1.8 | Moderate | EPA Zone 2 | 4 |
| Benewah County | 2.6 pCi/L | 1.8 | Moderate | EPA Zone 1 | 5 |
| Adams County | 2.6 pCi/L | 1.6 | Moderate | EPA Zone 3 | 4 |
| Bonner County | 2.6 pCi/L | 1.7 | Moderate | EPA Zone 1 | 13 |
| Boundary County | 2.5 pCi/L | 2.0 | Moderate | EPA Zone 1 | 3 |
| Lincoln County | 2.5 pCi/L | 1.3 | Moderate | EPA Zone 2 | 3 |
| Jerome County | 2.4 pCi/L | 1.4 | Moderate | EPA Zone 2 | 3 |
| Twin Falls County | 2.4 pCi/L | 1.5 | Moderate | EPA Zone 2 | 8 |
| Minidoka County | 2.4 pCi/L | 1.5 | Moderate | EPA Zone 2 | 3 |
| Latah County | 2.4 pCi/L | 1.6 | Moderate | EPA Zone 1 | 9 |
| Gooding County | 2.4 pCi/L | 1.3 | Moderate | EPA Zone 1 | 3 |
| Valley County | 2.4 pCi/L | 1.6 | Moderate | EPA Zone 1 | 3 |
| Gem County | 2.4 pCi/L | 1.6 | Moderate | EPA Zone 3 | 3 |
| Owyhee County | 2.3 pCi/L | 1.4 | Moderate | EPA Zone 2 | 7 |
| Ada County | 2.3 pCi/L | 1.6 | Moderate | EPA Zone 2 | 14 |
| Lewis County | 2.3 pCi/L | 1.3 | Moderate | EPA Zone 3 | 2 |
| Payette County | 2.1 pCi/L | 1.3 | Moderate | EPA Zone 2 | 3 |
| Idaho County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 1 | 12 |
| Washington County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 3 | 3 |
| Nez Perce County | 2.0 pCi/L | 1.2 | Moderate | EPA Zone 3 | 8 |
| Canyon County | 1.9 pCi/L | 1.3 | Low | EPA Zone 2 | 9 |
| Clearwater County | 1.8 pCi/L | 1.3 | Low | EPA Zone 1 | 5 |
Idaho radon questions
- Is radon high in Idaho?
- Idaho's population-weighted predicted basement average is 2.6 pCi/L, about 1.4× the US average of 1.8. 2 of its 44 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 40 are in the 2-4 "consider fixing" range and 2 are below 2. 3.3% of Idaho ZIP codes are predicted at 4 or higher.
- Which Idaho county has the highest radon?
- Teton County has the highest predicted basement average in Idaho at 4.4 pCi/L (EPA Zone 2). The lowest is Clearwater County at 1.8 pCi/L. These are modeled area averages; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Idaho?
- 19 of Idaho's 44 counties (43%) are EPA Zone 1 (highest potential), 20 are Zone 2 and 5 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 Idaho?
- Yes - with some urgency. Idaho's predicted average is in the moderate range, and 94.7% of its ZIP codes are predicted at 2 pCi/L or higher. A short-term charcoal kit or a continuous digital monitor will tell you your actual level within days.
Idaho radon program
Many states offer free or discounted test kits and keep lists of certified mitigators. Find the Idaho radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.