Radon levels in Colorado: Moderate
The model predicts a population-weighted basement average of 2.6 pCi/L across Colorado's 64 counties - about 1.4× the US average of 1.8 pCi/L. Above-ground floors average 2.0 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.
53 / 64
EPA Zone 1 counties (83%)
11 / 0
Zone 2 / Zone 3 counties
3
counties predicted ≥ 4 pCi/L
1.8%
of ZIP codes predicted ≥ 4 pCi/L
Colorado counties by predicted radon
Sorted highest to lowest predicted basement average. 64 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Pueblo County | 4.2 pCi/L | 2.5 | High | EPA Zone 1 | 12 |
| Chaffee County | 4.1 pCi/L | 3.3 | High | EPA Zone 1 | 3 |
| Teller County | 4.0 pCi/L | 2.9 | High | EPA Zone 1 | 4 |
| Gunnison County | 3.9 pCi/L | 2.9 | Moderate | EPA Zone 1 | 10 |
| Jackson County | 3.7 pCi/L | 2.4 | Moderate | EPA Zone 1 | 1 |
| Montrose County | 3.7 pCi/L | 2.8 | Moderate | EPA Zone 1 | 7 |
| Phillips County | 3.7 pCi/L | 2.4 | Moderate | EPA Zone 1 | 3 |
| Fremont County | 3.6 pCi/L | 2.4 | Moderate | EPA Zone 1 | 5 |
| Summit County | 3.5 pCi/L | 2.6 | Moderate | EPA Zone 1 | 4 |
| Washington County | 3.5 pCi/L | 2.2 | Moderate | EPA Zone 1 | 6 |
| Delta County | 3.5 pCi/L | 2.5 | Moderate | EPA Zone 1 | 6 |
| Las Animas County | 3.5 pCi/L | 2.4 | Moderate | EPA Zone 1 | 7 |
| Morgan County | 3.5 pCi/L | 2.1 | Moderate | EPA Zone 1 | 7 |
| Bent County | 3.4 pCi/L | 2.1 | Moderate | EPA Zone 1 | 4 |
| Park County | 3.4 pCi/L | 2.7 | Moderate | EPA Zone 1 | 6 |
| Otero County | 3.4 pCi/L | 2.0 | Moderate | EPA Zone 1 | 3 |
| Yuma County | 3.4 pCi/L | 2.0 | Moderate | EPA Zone 1 | 7 |
| Kiowa County | 3.3 pCi/L | 2.0 | Moderate | EPA Zone 1 | 4 |
| Ouray County | 3.3 pCi/L | 2.7 | Moderate | EPA Zone 1 | 2 |
| Crowley County | 3.3 pCi/L | 1.9 | Moderate | EPA Zone 1 | 3 |
| Lake County | 3.3 pCi/L | 2.7 | Moderate | EPA Zone 1 | 2 |
| Kit Carson County | 3.3 pCi/L | 2.0 | Moderate | EPA Zone 1 | 6 |
| Gilpin County | 3.3 pCi/L | 2.3 | Moderate | EPA Zone 1 | 2 |
| Logan County | 3.3 pCi/L | 2.1 | Moderate | EPA Zone 1 | 8 |
| Huerfano County | 3.3 pCi/L | 2.1 | Moderate | EPA Zone 1 | 4 |
| Hinsdale County | 3.2 pCi/L | 2.7 | Moderate | EPA Zone 2 | 1 |
| Baca County | 3.2 pCi/L | 2.0 | Moderate | EPA Zone 1 | 6 |
| Cheyenne County | 3.2 pCi/L | 1.9 | Moderate | EPA Zone 1 | 3 |
| Mineral County | 3.1 pCi/L | 2.4 | Moderate | EPA Zone 2 | 1 |
| Custer County | 3.1 pCi/L | 2.6 | Moderate | EPA Zone 1 | 2 |
| Dolores County | 3.1 pCi/L | 2.2 | Moderate | EPA Zone 1 | 4 |
| Larimer County | 3.1 pCi/L | 2.2 | Moderate | EPA Zone 1 | 17 |
| San Juan County | 3.1 pCi/L | 2.6 | Moderate | EPA Zone 2 | 1 |
| Grand County | 3.1 pCi/L | 2.4 | Moderate | EPA Zone 1 | 8 |
| Montezuma County | 3.1 pCi/L | 2.1 | Moderate | EPA Zone 1 | 6 |
| Lincoln County | 3.1 pCi/L | 1.9 | Moderate | EPA Zone 1 | 6 |
| Garfield County | 3.0 pCi/L | 2.3 | Moderate | EPA Zone 1 | 6 |
| La Plata County | 3.0 pCi/L | 2.4 | Moderate | EPA Zone 1 | 5 |
| Pitkin County | 3.0 pCi/L | 2.5 | Moderate | EPA Zone 1 | 4 |
| Rio Blanco County | 3.0 pCi/L | 2.2 | Moderate | EPA Zone 1 | 3 |
| Clear Creek County | 3.0 pCi/L | 2.6 | Moderate | EPA Zone 1 | 6 |
| Moffat County | 2.9 pCi/L | 2.5 | Moderate | EPA Zone 1 | 4 |
| San Miguel County | 2.9 pCi/L | 2.3 | Moderate | EPA Zone 1 | 5 |
| Routt County | 2.9 pCi/L | 2.5 | Moderate | EPA Zone 2 | 7 |
| Prowers County | 2.9 pCi/L | 1.9 | Moderate | EPA Zone 1 | 4 |
| Sedgwick County | 2.8 pCi/L | 1.7 | Moderate | EPA Zone 1 | 3 |
| Weld County | 2.7 pCi/L | 1.9 | Moderate | EPA Zone 1 | 29 |
| Mesa County | 2.7 pCi/L | 2.2 | Moderate | EPA Zone 1 | 16 |
| Archuleta County | 2.7 pCi/L | 2.3 | Moderate | EPA Zone 2 | 1 |
| Eagle County | 2.5 pCi/L | 2.2 | Moderate | EPA Zone 2 | 6 |
| Jefferson County | 2.5 pCi/L | 2.1 | Moderate | EPA Zone 1 | 22 |
| Elbert County | 2.5 pCi/L | 2.1 | Moderate | EPA Zone 1 | 7 |
| Denver County | 2.5 pCi/L | 1.9 | Moderate | EPA Zone 1 | 26 |
| Rio Grande County | 2.5 pCi/L | 2.2 | Moderate | EPA Zone 2 | 3 |
| Arapahoe County | 2.5 pCi/L | 1.9 | Moderate | EPA Zone 1 | 17 |
| Boulder County | 2.4 pCi/L | 1.9 | Moderate | EPA Zone 1 | 14 |
| Saguache County | 2.4 pCi/L | 1.9 | Moderate | EPA Zone 2 | 4 |
| Costilla County | 2.4 pCi/L | 1.7 | Moderate | EPA Zone 2 | 4 |
| Conejos County | 2.3 pCi/L | 1.7 | Moderate | EPA Zone 2 | 2 |
| El Paso County | 2.3 pCi/L | 1.9 | Moderate | EPA Zone 1 | 37 |
| Broomfield County | 2.3 pCi/L | 2.0 | Moderate | EPA Zone 1 | 2 |
| Alamosa County | 2.3 pCi/L | 1.8 | Moderate | EPA Zone 2 | 3 |
| Adams County | 2.2 pCi/L | 1.9 | Moderate | EPA Zone 1 | 19 |
| Douglas County | 1.8 pCi/L | 1.7 | Low | EPA Zone 1 | 13 |
Colorado radon questions
- Is radon high in Colorado?
- Colorado's population-weighted predicted basement average is 2.6 pCi/L, about 1.4× the US average of 1.8. 3 of its 64 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 60 are in the 2-4 "consider fixing" range and 1 are below 2. 1.8% of Colorado ZIP codes are predicted at 4 or higher.
- Which Colorado county has the highest radon?
- Pueblo County has the highest predicted basement average in Colorado at 4.2 pCi/L (EPA Zone 1). The lowest is Douglas 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 Colorado?
- 53 of Colorado's 64 counties (83%) are EPA Zone 1 (highest potential), 11 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 Colorado?
- Yes - with some urgency. Colorado's predicted average is in the moderate range, and 94.9% 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.
Colorado radon program
Many states offer free or discounted test kits and keep lists of certified mitigators. Find the Colorado radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.