Counties with the Highest Radon Potential in New Hampshire
The top 10 of 10 New Hampshire counties on GIS Map, ranked by EPA radon zone, where zone 1 carries the highest predicted indoor radon potential and zone 3 the lowest.
| # | County | EPA radon zone |
|---|---|---|
| 1 | Belknap County | 2 |
| 2 | Cheshire County | 2 |
| 3 | Coos County | 2 |
| 4 | Grafton County | 2 |
| 5 | Hillsborough County | 2 |
| 6 | Merrimack County | 2 |
| 7 | Rockingham County | 2 |
| 8 | Strafford County | 2 |
| 9 | Sullivan County | 2 |
| 10 | Carroll County | 1 |
Source: EPA Map of Radon Zones (September 2025). All counties with data are ranked. Estimates carry margins of error.
Citing this page: GIS Map, “Counties with the Highest Radon Potential in New Hampshire”, https://gismap.land/rankings/new-hampshire/highest-radon-counties. Figures from EPA Map of Radon Zones (September 2025).
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