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State overview
Radon in Idaho
Of Idaho's 44 counties and county equivalents, EPA places 19 in Zone 1, 20 in Zone 2, 5 in Zone 3. Zones are county-wide predictions; testing is the only way to know your home's level.
Radon in the news
Idaho stories
- Hidden danger: High radon levels in Idaho pose cancer risksKTVB · 2025-02-04
Headlines link to the original publishers via Google News. Updated 2026-10-27.
All 44 counties
| County | EPA zone |
|---|---|
| Ada County | Zone 2 |
| Adams County | Zone 3 |
| Bannock County | Zone 2 |
| Bear Lake County | Zone 2 |
| Benewah County | Zone 1 |
| Bingham County | Zone 2 |
| Blaine County | Zone 1 |
| Boise County | Zone 1 |
| Bonner County | Zone 1 |
| Bonneville County | Zone 2 |
| Boundary County | Zone 1 |
| Butte County | Zone 1 |
| Camas County | Zone 1 |
| Canyon County | Zone 2 |
| Caribou County | Zone 2 |
| Cassia County | Zone 2 |
| Clark County | Zone 1 |
| Clearwater County | Zone 1 |
| Custer County | Zone 1 |
| Elmore County | Zone 1 |
| Franklin County | Zone 2 |
| Fremont County | Zone 1 |
| Gem County | Zone 3 |
| Gooding County | Zone 1 |
| Idaho County | Zone 1 |
| Jefferson County | Zone 2 |
| Jerome County | Zone 2 |
| Kootenai County | Zone 1 |
| Latah County | Zone 1 |
| Lemhi County | Zone 1 |
| Lewis County | Zone 3 |
| Lincoln County | Zone 2 |
| Madison County | Zone 2 |
| Minidoka County | Zone 2 |
| Nez Perce County | Zone 3 |
| Oneida County | Zone 2 |
| Owyhee County | Zone 2 |
| Payette County | Zone 2 |
| Power County | Zone 2 |
| Shoshone County | Zone 1 |
| Teton County | Zone 2 |
| Twin Falls County | Zone 2 |
| Valley County | Zone 1 |
| Washington County | Zone 3 |
Source: EPA radon zones spreadsheet (EPA 402/A-16/001).