Radon levels in New Hampshire: Moderate
The model predicts a population-weighted basement average of 2.1 pCi/L (model estimate) 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
Test New Hampshire - the EPA says "consider fixing" in this range
The predicted basement average here is 2.1 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.
Monitor link goes to the Airthings store - use code RADONGRADE-10OFF at checkout for 10% off any Airthings monitor.
Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.
Affiliate links: we may earn a commission from Airthings or Amazon at no extra cost to you.
What the data says about radon in New Hampshire
On the EPA's 1993 radon zone map, 1 of New Hampshire's 10 counties is EPA Zone 1 (10%), 9 are Zone 2 and 0 are Zone 3. Zone 2 (predicted screening average of 2-4 pCi/L) is the most common designation, with the 1 Zone 1 county marking where the EPA expected the highest potential. That classification has not been revised since 1993; it describes counties, not homes, and elevated readings turn up in Zone 3 counties every year.
New Hampshire models out at 2.1 pCi/L predicted basement average (moderate; 1.2× the US population-weighted average of 1.8). Of the 10 counties with predictions, 0 are predicted at or above 4 pCi/L, 6 in the 2-4 band and 4 below 2. The county range is narrow: from Sullivan County at 1.58 to Carroll County at 2.30 pCi/L, a spread of only 0.72.
At ZIP-code resolution, 0.4% of New Hampshire ZIPs are predicted at 4 pCi/L or higher in the basement and 49.3% at 2 or higher - below the national 4.2% at the action level but near the national 48.7% at 2 pCi/L. The 4+ ZIPs are where a first test is most urgent; the 2-4 ZIPs are where results most often surprise people.
New Hampshire counties by predicted radon
Sorted highest to lowest predicted basement average (model estimate). 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 |
Radon levels in New Hampshire cities
The 3 most-populous New Hampshire places among the 1,000 largest US cities (Census incorporated places and CDPs), by population. City figures are ZIP-land-weighted means of the model's ZIP predictions (model estimate).
| City | Population | Predicted basement | Upstairs | Grade | ZIPs ≥ 4 |
|---|---|---|---|---|---|
| Manchester | 115,474 | 2.0 pCi/L | 1.3 | Moderate | 0% |
| Nashua | 91,003 | 2.1 pCi/L | 1.3 | Moderate | 0% |
| Concord | 44,629 | 2.0 pCi/L | 1.3 | Moderate | 0% |
Highest-radon ZIP codes in New Hampshire
The 10 New Hampshire ZIP codes with the highest predicted basement average (model estimate), out of 229 modeled. A ZIP average is still an area figure - neighboring homes routinely test several pCi/L apart.
| ZIP | County | Predicted basement | Upstairs | Grade |
|---|---|---|---|---|
| 03034 | Rockingham County | 4.2 pCi/L | 2.1 | High |
| 03593 | Coos County | 3.6 pCi/L | 1.9 | Moderate |
| 03848 | Rockingham County | 3.5 pCi/L | 1.4 | Moderate |
| 03818 | Carroll County | 3.5 pCi/L | 1.6 | Moderate |
| 03581 | Coos County | 3.4 pCi/L | 1.4 | Moderate |
| 03046 | Merrimack County | 3.2 pCi/L | 1.9 | Moderate |
| 03077 | Rockingham County | 3.2 pCi/L | 1.4 | Moderate |
| 03076 | Hillsborough County | 3.2 pCi/L | 1.7 | Moderate |
| 03855 | Strafford County | 3.1 pCi/L | 1.5 | Moderate |
| 03884 | Strafford County | 3.0 pCi/L | 1.7 | Moderate |
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 area figures; 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
State programs keep lists of certified testers and mitigators and sometimes run kit programs. We link only pages we could verify, and New Hampshire's program page did not respond when we checked, so start from the EPA state radon contacts page. Then read how to test and what mitigation costs.