Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
Locations and reports
Radon Levels in Sullivan County, New Hampshire
EPA puts Sullivan County in Zone 2, its middle radon zone, and 23.3% of its 60 reported radon tests (2021) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
23.3%
19.4 pts below NH
- Sullivan
- 23.3%
- NH
- 42.7%
60 tests, 2021
Median result
2.7pCi/L
Below action level
- Sullivan
- 2.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2021
Tests reported
60
9th of 10 by tests
- Sullivan
- 60
- Rockingham
- 638
Reported to CDC before any fix, 2021
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in NH
9 of 10
Lowest quarter
- Sullivan
- 23.3%
- Carroll
- 54.0%
By share, of 10 with 30+ tests
Read a result for Sullivan County
Starts at Sullivan County's median, 2.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.7 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Sullivan County's median reported result, 2021.
The data
Sullivan County, At a glance
Sullivan County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Sullivan County is a
USGS geologic potential: Moderate across 88% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Sullivan County, 2021
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2018 | 22.6% |
| 2019 | 36.1% |
| 2020 | 27.0% |
| 2021 | 23.3% |
2021: 23.3%. Across these years the share ran from 22.6% to 36.1%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 60 tests reported to CDC for Sullivan County over 2021, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2021. Measured data period: 2005 to 2021 (every CDC figure on file).
Sullivan County, Compared
Sullivan County radon figures, compared
Calculated by Radon411Sullivan County's 60 reported tests in 2021 had a middle value of 2.7 pCi/L and a maximum of 12.4 pCi/L, and 23.3% reached 4 pCi/L. New Hampshire as a whole (10 New Hampshire counties, pooled) comes to 42.7%: 19.4 points higher than here.
Among its state's counties it ranks 9th of 10 New Hampshire counties with 30 or more tests for the same period. Statewide for the same period, Carroll County reported the highest share (54.0%) and Cheshire County the lowest (19.4%).
Below the action level, 21 tests (35.0%) came in under 2 pCi/L, against 32.3% statewide, and 25 tests (41.7%) fell between 2 and 4, against 25.0% statewide. The busiest year on file was 2021, with 60 tests reported; the quietest, 2019, had 36.
EPA's 1993 zone map puts Sullivan County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 88% of the county's land moderate radon potential.
Next door, the shares run from 12.0% in Windham County, VT to 44.4% in Grafton County, with Cheshire County, Windsor County, VT and Windham County, VT below Sullivan County. Over 4 years of annual figures the share held within 2 points, from 22.6% in 2018 to 23.3% in 2021; its peak was 36.1% in 2019.
CDC also counts 13 tests taken after mitigation in Sullivan County for the same period: tests in homes where a fix was already in.
Sullivan CountyNew Hampshire, pooled
23.3% % of tests42.7% % of tests
| Year | Tests | Sullivan County, at or above 4 pCi/L | New Hampshire, pooled |
|---|---|---|---|
| 2018 | 53 | 22.6% | 34.6% |
| 2019 | 36 | 36.1% | 40.6% |
| 2020 | 37 | 27.0% | 40.2% |
| 2021 | 60 | 23.3% | 42.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Sullivan County, Geology
The ground under Sullivan County
PredictedMost of the ground under Sullivan County is one class on USGS's geologic map: 88.2% of its land is moderate radon potential, with 1.1% high and 10.7% low. The map puts 78.3% of Sullivan County in the area it calls Eastern New England Upland and 10.7% in Eastern New England Upland, with 4 smaller areas beside them. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 8, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Eastern New England Upland | Late Cambrian-Early Devonian limestone, conglomerate, phyllite, schist, slate. | Moderate | 10 | 78.3% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite. | Low | 8 | 10.7% |
| Eastern New England Upland | Middle to Late Ordovician intrusive rocks ranging from gabbro to syenite. | Moderate | 10 | 4.6% |
| Eastern New England Upland | Jurassic-Cretaceous rocks of the White Mountain and New England-Quebec igneous succession. | Moderate | 10 | 2.5% |
| Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley | Phyllite, calcareous and aluminous schist, quartzite, slate, granofels, metavolcanic rocks. | Moderate | 10 | 2.4% |
| Eastern New England Upland | Devonian-Carboniferous two-mica granite. | High | 13 | 1.1% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Sullivan County beside the ground around it
New Hampshire as a whole has more high-potential ground than Sullivan County: 18.8% of its land, against 1.1% here. Of the 6 counties that border it, 4 have more high-potential ground, Hillsborough County the most at 20.4%.
The map rates the ground, not the air in any home.
Local help
Sullivan County, Local resources
Radon testing and mitigation in Sullivan County
- New Hampshire Radon ProgramNew Hampshire Radon Program, run by New Hampshire Department of Health and Human Services, does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in New Hampshire.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The NH Radon Program provides free radon test kits to NH residents.
- Compare kits
- See the New Hampshire directoryNo professionals are listed in New Hampshire yet. The state program can point you to registered testers and mitigators.
What New Hampshire's program says
- Licensing of radon professionals
There is no requirement in New Hampshire for those professionals testing for radon to be certified but it is recommended to use a nationally certified radon measurement professional especially if a real estate transaction is involved.
What it means
Sullivan County, Questions
Questions about radon in Sullivan County
Are radon levels high in Sullivan County?
In 2021, 23.3% of the radon tests reported to CDC for Sullivan County, New Hampshire were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.7 pCi/L. Of 10 New Hampshire counties with 30 or more tests for the same period, 8 reported a higher share; pooled, the state comes to 42.7%.
Which counties border Sullivan County?
Sullivan County borders 6 counties: Windsor County, VT, Cheshire County, NH, Merrimack County, NH, Windham County, VT, Hillsborough County, NH and Grafton County, NH.
Products
Sullivan County, Products
Testing a home in Sullivan County
In Sullivan County, 23.3% of 60 tests reported to CDC in 2021 reached 4 pCi/L, against 42.7% pooled across New Hampshire. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Sullivan County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
MonitorAranet
Radon Plus battery digital radon monitor with an e-ink screen
- C-NRPP 2024/25: Approved
- Battery
- Bluetooth
- Alarm
- Screen, app
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Sullivan County, Bordering counties
Counties bordering Sullivan County
Calculated by Radon411- Radon levels in Grafton County, NHEPA zone 2
44.4%at or above 4 pCi/L
Median 3.0 pCi/L · 142 tests · 21.1 points above Sullivan County
- Radon levels in Hillsborough County, NHEPA zone 2
41.5%at or above 4 pCi/L
Median 3.2 pCi/L · 610 tests · 18.2 points above Sullivan County
- Radon levels in Merrimack County, NHEPA zone 2
31.6%at or above 4 pCi/L
Median 2.2 pCi/L · 187 tests · 8.3 points above Sullivan County
- Radon levels in Cheshire County, NHEPA zone 2
19.4%at or above 4 pCi/L
Median 2.1 pCi/L · 103 tests · 3.9 points below Sullivan County
- Radon levels in Windsor County, VTEPA zone 2
18.3%at or above 4 pCi/L
Median 1.6 pCi/L · 175 tests · 5.0 points below Sullivan County
- Radon levels in Windham County, VTEPA zone 2
12.0%at or above 4 pCi/L
Median 1.5 pCi/L · 117 tests · 11.3 points below Sullivan County
Sullivan County, Cities and towns
Cities and towns in Sullivan County
The Census Bureau estimates 43,961 residents in Sullivan County for July 1, 2025, 888 more than in 2020 (+2.1%). That works out to 82 people per square mile of land. Claremont, its one incorporated place, has 13,032 residents, 29.6% of the total. CDC's 60 reported tests for 2021 work out to 1.4 per 1,000 residents (2025 estimate), close to New Hampshire's 1.6.
Claremont is the one incorporated place here; CDC publishes no figure by town, so it reads Sullivan County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Claremont | 13,032 | +0.6% | 29.6% |
One incorporated place, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Sullivan County, Homes
Homes in Sullivan County
Of Sullivan County's 21,905 homes, 73% are detached houses, against 63% across New Hampshire; 10% are in buildings of five or more homes. Half of its homes were built before 1974, close to New Hampshire's 1978: 36% date from before 1960 and 12% from 2000 or later. 75% of occupied homes are lived in by their owner (New Hampshire: 73%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Sullivan County | New Hampshire |
|---|---|---|
| Housing units | 21,905 | 644,253 |
| Detached houses | 73% | 63% |
| In buildings of 5 or more | 10% | 15% |
| Mobile homes | 8% | 5% |
| Built before 1960 | 36% | 29% |
| Built since 2000 | 12% | 18% |
| Middle year built | 1974 | 1978 |
| Owner-occupied | 75% | 73% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.