New Hampshire Radon Levels
1Zone 1 (High)
9Zone 2 (Moderate)
0Zone 3 (Low)
10% of counties in New Hampshire 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 |
|---|---|---|
| Belknap County | Zone 2 | Moderate Potential |
| Carroll County | Zone 1 | Highest Potential |
| Cheshire County | Zone 2 | Moderate Potential |
| Coos County | Zone 2 | Moderate Potential |
| Grafton County | Zone 2 | Moderate Potential |
| Hillsborough County | Zone 2 | Moderate Potential |
| Merrimack County | Zone 2 | Moderate Potential |
| Rockingham County | Zone 2 | Moderate Potential |
| Strafford County | Zone 2 | Moderate Potential |
| Sullivan County | Zone 2 | Moderate Potential |