Home › Washington
State overview
Radon in Washington
Of Washington's 39 counties and county equivalents, EPA places 7 in Zone 1, 14 in Zone 2, 18 in Zone 3. Zones are county-wide predictions; testing is the only way to know your home's level.
Radon in the news
Washington stories
- Washington State Department of Health Announces 2026 Northwest Radon Poster Contest WinnersWashington State Department of Health (.gov) · 2026-04-16
Headlines link to the original publishers via Google News. Updated 2026-10-27.
All 39 counties
| County | EPA zone |
|---|---|
| Adams County | Zone 2 |
| Asotin County | Zone 2 |
| Benton County | Zone 2 |
| Chelan County | Zone 3 |
| Clallam County | Zone 3 |
| Clark County | Zone 1 |
| Columbia County | Zone 2 |
| Cowlitz County | Zone 3 |
| Douglas County | Zone 2 |
| Ferry County | Zone 1 |
| Franklin County | Zone 2 |
| Garfield County | Zone 2 |
| Grant County | Zone 2 |
| Grays Harbor County | Zone 3 |
| Island County | Zone 3 |
| Jefferson County | Zone 3 |
| King County | Zone 3 |
| Kitsap County | Zone 3 |
| Kittitas County | Zone 2 |
| Klickitat County | Zone 2 |
| Lewis County | Zone 3 |
| Lincoln County | Zone 2 |
| Mason County | Zone 3 |
| Okanogan County | Zone 1 |
| Pacific County | Zone 3 |
| Pend Oreille County | Zone 1 |
| Pierce County | Zone 3 |
| San Juan County | Zone 3 |
| Skagit County | Zone 3 |
| Skamania County | Zone 1 |
| Snohomish County | Zone 3 |
| Spokane County | Zone 1 |
| Stevens County | Zone 1 |
| Thurston County | Zone 3 |
| Wahkiakum County | Zone 3 |
| Walla Walla County | Zone 2 |
| Whatcom County | Zone 3 |
| Whitman County | Zone 2 |
| Yakima County | Zone 2 |
Source: EPA radon zones spreadsheet (EPA 402/A-16/001).