Radon zones in Colorado
Last updated
EPA’s Map of Radon Zones places 64 Colorado counties in its three radon potential zones: 53 in Zone 1 (highest), 11 in Zone 2 (moderate), and 0 in Zone 3 (low).
What this means for Colorado homes
Most Colorado counties fall in Zone 1. EPA predicts average indoor screening levels above 4 pCi/L across much of Colorado, so elevated radon is common. Testing is especially worthwhile here, and radon-resistant construction features make sense for new homes.
EPA’s guidance is the same everywhere: test your home, fix it if the level is 4 pCi/L or higher, and consider fixing between 2 and 4 pCi/L. The zone map is from 1993 and should not be used to decide whether a single home needs testing.
Colorado radon program
EPA lists the following state contact for Colorado: CO Department of Public Health & Environment (CDPHE), phone 800-846-3986. Website: cdphe.colorado.gov/hm/radon. State programs can tell you about local testing data, free or discounted test kits, disclosure rules for home sales, and credentialed radon professionals.
Colorado counties and their EPA radon zones
| County | EPA radon zone |
|---|---|
| Adams County | Zone 1 |
| Alamosa County | Zone 2 |
| Arapahoe County | Zone 1 |
| Archuleta County | Zone 2 |
| Baca County | Zone 1 |
| Bent County | Zone 1 |
| Boulder County | Zone 1 |
| Broomfield County | Zone 1 |
| Chaffee County | Zone 1 |
| Cheyenne County | Zone 1 |
| Clear Creek County | Zone 1 |
| Conejos County | Zone 2 |
| Costilla County | Zone 2 |
| Crowley County | Zone 1 |
| Custer County | Zone 1 |
| Delta County | Zone 1 |
| Denver County | Zone 1 |
| Dolores County | Zone 1 |
| Douglas County | Zone 1 |
| Eagle County | Zone 2 |
| El Paso County | Zone 1 |
| Elbert County | Zone 1 |
| Fremont County | Zone 1 |
| Garfield County | Zone 1 |
| Gilpin County | Zone 1 |
| Grand County | Zone 1 |
| Gunnison County | Zone 1 |
| Hinsdale County | Zone 2 |
| Huerfano County | Zone 1 |
| Jackson County | Zone 1 |
| Jefferson County | Zone 1 |
| Kiowa County | Zone 1 |
| Kit Carson County | Zone 1 |
| La Plata County | Zone 1 |
| Lake County | Zone 1 |
| Larimer County | Zone 1 |
| Las Animas County | Zone 1 |
| Lincoln County | Zone 1 |
| Logan County | Zone 1 |
| Mesa County | Zone 1 |
| Mineral County | Zone 2 |
| Moffat County | Zone 1 |
| Montezuma County | Zone 1 |
| Montrose County | Zone 1 |
| Morgan County | Zone 1 |
| Otero County | Zone 1 |
| Ouray County | Zone 1 |
| Park County | Zone 1 |
| Phillips County | Zone 1 |
| Pitkin County | Zone 1 |
| Prowers County | Zone 1 |
| Pueblo County | Zone 1 |
| Rio Blanco County | Zone 1 |
| Rio Grande County | Zone 2 |
| Routt County | Zone 2 |
| Saguache County | Zone 2 |
| San Juan County | Zone 2 |
| San Miguel County | Zone 1 |
| Sedgwick County | Zone 1 |
| Summit County | Zone 1 |
| Teller County | Zone 1 |
| Washington County | Zone 1 |
| Weld County | Zone 1 |
| Yuma County | Zone 1 |
County names follow the 2020 Census. Zones from the EPA Map of Radon Zones (text version). Rows marked “zone of” use the zone EPA gave the predecessor or surrounding county.
Next steps: read how to test your home, check a result with the level calculator, or look up a single address by ZIP code.