Wisconsin Radon Levels
28Zone 1 (High)
44Zone 2 (Moderate)
0Zone 3 (Low)
39% of counties in Wisconsin are classified as EPA Zone 1 (highest radon potential), meaning predicted average indoor radon levels exceed 4 pCi/L — the EPA action level. The EPA recommends that all homes be tested for radon, regardless of zone classification.
| County | EPA Zone | Risk Level |
|---|---|---|
| Adams County | Zone 2 | Moderate Potential |
| Ashland County | Zone 2 | Moderate Potential |
| Barron County | Zone 2 | Moderate Potential |
| Bayfield County | Zone 2 | Moderate Potential |
| Brown County | Zone 2 | Moderate Potential |
| Buffalo County | Zone 1 | Highest Potential |
| Burnett County | Zone 2 | Moderate Potential |
| Calumet County | Zone 2 | Moderate Potential |
| Chippewa County | Zone 2 | Moderate Potential |
| Clark County | Zone 2 | Moderate Potential |
| Columbia County | Zone 2 | Moderate Potential |
| Crawford County | Zone 1 | Highest Potential |
| Dane County | Zone 1 | Highest Potential |
| Dodge County | Zone 1 | Highest Potential |
| Door County | Zone 1 | Highest Potential |
| Douglas County | Zone 2 | Moderate Potential |
| Dunn County | Zone 2 | Moderate Potential |
| Eau Claire County | Zone 2 | Moderate Potential |
| Florence County | Zone 2 | Moderate Potential |
| Fond du Lac County | Zone 1 | Highest Potential |
| Forest County | Zone 2 | Moderate Potential |
| Grant County | Zone 1 | Highest Potential |
| Green County | Zone 1 | Highest Potential |
| Green Lake County | Zone 1 | Highest Potential |
| Iowa County | Zone 1 | Highest Potential |
| Iron County | Zone 2 | Moderate Potential |
| Jackson County | Zone 2 | Moderate Potential |
| Jefferson County | Zone 1 | Highest Potential |
| Juneau County | Zone 2 | Moderate Potential |
| Kenosha County | Zone 2 | Moderate Potential |
| Kewaunee County | Zone 2 | Moderate Potential |
| La Crosse County | Zone 2 | Moderate Potential |
| Lafayette County | Zone 1 | Highest Potential |
| Langlade County | Zone 1 | Highest Potential |
| Lincoln County | Zone 2 | Moderate Potential |
| Manitowoc County | Zone 2 | Moderate Potential |
| Marathon County | Zone 1 | Highest Potential |
| Marinette County | Zone 2 | Moderate Potential |
| Marquette County | Zone 2 | Moderate Potential |
| Menominee County | Zone 1 | Highest Potential |
| Milwaukee County | Zone 2 | Moderate Potential |
| Monroe County | Zone 2 | Moderate Potential |
| Oconto County | Zone 2 | Moderate Potential |
| Oneida County | Zone 2 | Moderate Potential |
| Outagamie County | Zone 2 | Moderate Potential |
| Ozaukee County | Zone 2 | Moderate Potential |
| Pepin County | Zone 1 | Highest Potential |
| Pierce County | Zone 1 | Highest Potential |
| Polk County | Zone 2 | Moderate Potential |
| Portage County | Zone 1 | Highest Potential |
| Price County | Zone 2 | Moderate Potential |
| Racine County | Zone 2 | Moderate Potential |
| Richland County | Zone 1 | Highest Potential |
| Rock County | Zone 1 | Highest Potential |
| Rusk County | Zone 2 | Moderate Potential |
| St. Croix County | Zone 1 | Highest Potential |
| Sauk County | Zone 2 | Moderate Potential |
| Sawyer County | Zone 2 | Moderate Potential |
| Shawano County | Zone 1 | Highest Potential |
| Sheboygan County | Zone 2 | Moderate Potential |
| Taylor County | Zone 2 | Moderate Potential |
| Trempealeau County | Zone 2 | Moderate Potential |
| Vernon County | Zone 1 | Highest Potential |
| Vilas County | Zone 2 | Moderate Potential |
| Walworth County | Zone 1 | Highest Potential |
| Washburn County | Zone 2 | Moderate Potential |
| Washington County | Zone 1 | Highest Potential |
| Waukesha County | Zone 1 | Highest Potential |
| Waupaca County | Zone 1 | Highest Potential |
| Waushara County | Zone 2 | Moderate Potential |
| Winnebago County | Zone 2 | Moderate Potential |
| Wood County | Zone 1 | Highest Potential |