Maine Radon Levels
12Zone 1 (High)
4Zone 2 (Moderate)
0Zone 3 (Low)
75% of counties in Maine 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 |
|---|---|---|
| Androscoggin County | Zone 1 | Highest Potential |
| Aroostook County | Zone 1 | Highest Potential |
| Cumberland County | Zone 1 | Highest Potential |
| Franklin County | Zone 1 | Highest Potential |
| Hancock County | Zone 1 | Highest Potential |
| Kennebec County | Zone 1 | Highest Potential |
| Knox County | Zone 2 | Moderate Potential |
| Lincoln County | Zone 1 | Highest Potential |
| Oxford County | Zone 1 | Highest Potential |
| Penobscot County | Zone 1 | Highest Potential |
| Piscataquis County | Zone 1 | Highest Potential |
| Sagadahoc County | Zone 2 | Moderate Potential |
| Somerset County | Zone 1 | Highest Potential |
| Waldo County | Zone 2 | Moderate Potential |
| Washington County | Zone 2 | Moderate Potential |
| York County | Zone 1 | Highest Potential |