Radon levels in New Hampshire: Moderate
The model predicts a population-weighted basement average of 2.1 pCi/L across New Hampshire's 10 counties - about 1.2× the US average of 1.8 pCi/L. Above-ground floors average 1.3 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
1 / 10
EPA Zone 1 counties (10%)
9 / 0
Zone 2 / Zone 3 counties
0
counties predicted ≥ 4 pCi/L
0.4%
of ZIP codes predicted ≥ 4 pCi/L
New Hampshire counties by predicted radon
Sorted highest to lowest predicted basement average. 10 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Carroll County | 2.3 pCi/L | 1.3 | Moderate | EPA Zone 1 | 25 |
| Rockingham County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 2 | 36 |
| Strafford County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 2 | 16 |
| Coos County | 2.1 pCi/L | 1.1 | Moderate | EPA Zone 2 | 11 |
| Hillsborough County | 2.1 pCi/L | 1.4 | Moderate | EPA Zone 2 | 34 |
| Merrimack County | 2.1 pCi/L | 1.3 | Moderate | EPA Zone 2 | 24 |
| Grafton County | 1.9 pCi/L | 1.1 | Low | EPA Zone 2 | 33 |
| Cheshire County | 1.8 pCi/L | 1.1 | Low | EPA Zone 2 | 24 |
| Belknap County | 1.8 pCi/L | 1.2 | Low | EPA Zone 2 | 13 |
| Sullivan County | 1.6 pCi/L | 1.0 | Low | EPA Zone 2 | 13 |
New Hampshire radon questions
- Is radon high in New Hampshire?
- New Hampshire's population-weighted predicted basement average is 2.1 pCi/L, about 1.2× the US average of 1.8. 0 of its 10 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 6 are in the 2-4 "consider fixing" range and 4 are below 2. 0.4% of New Hampshire ZIP codes are predicted at 4 or higher.
- Which New Hampshire county has the highest radon?
- Carroll County has the highest predicted basement average in New Hampshire at 2.3 pCi/L (EPA Zone 1). The lowest is Sullivan County at 1.6 pCi/L. These are modeled area averages; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in New Hampshire?
- 1 of New Hampshire's 10 counties (10%) are EPA Zone 1 (highest potential), 9 are Zone 2 and 0 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in New Hampshire?
- Yes - with some urgency. New Hampshire's predicted average is in the moderate range, and 49.3% of its ZIP codes are predicted at 2 pCi/L or higher. A short-term charcoal kit or a continuous digital monitor will tell you your actual level within days.
New Hampshire radon program
Many states offer free or discounted test kits and keep lists of certified mitigators. Find the New Hampshire radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.