Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
Locations and reports
Radon Levels in Strafford County, New Hampshire
EPA puts Strafford County in Zone 2, its middle radon zone, and high results are common there: 47.9% of the 213 radon tests reported to CDC (2021) came back 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
47.9%
5.2 pts above NH
- Strafford
- 47.9%
- NH
- 42.7%
213 tests, 2021
Median result
3.6pCi/L
Below action level
- Strafford
- 3.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2021
Tests reported
213
3rd of 10 by tests
- Strafford
- 213
- 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
4 of 10
Middle half
- Strafford
- 47.9%
- Carroll
- 54.0%
By share, of 10 with 30+ tests
Read a result for Strafford County
Starts at Strafford County's median, 3.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.6 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. Strafford County's median reported result, 2021.
The data
Strafford County, At a glance
Strafford County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Strafford County is a
USGS geologic potential: Moderate across 74% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Strafford County, 2021
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2018 | 43.1% |
| 2019 | 53.4% |
| 2020 | 40.8% |
| 2021 | 47.9% |
2021: 47.9%. Across these years the share ran from 40.8% to 53.4%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 213 tests reported to CDC for Strafford 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).
Strafford County, Compared
Strafford County radon figures, compared
Calculated by Radon411In Strafford County, about 5 in 10 reported tests in 2021 (102 of 213) were at or above EPA's action level. Against the national pool of 24.4%, the gap is 23.5 points higher. Across 10 New Hampshire counties pooled together, 42.7% of tests reached that level, so Strafford County runs 5.2 points above its state.
Of 4 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 31.6% (Merrimack County) to 54.0% (Carroll County). By share, Strafford County is 4th of 10 New Hampshire counties with 30 or more tests for the same period.
Year by year, 2018 opened at 43.1% and 2021 closed at 47.9% (up 4.8 points), with 2019 the high at 53.4%. Half the tests came in under 3.6 pCi/L and half over it; the single highest reached 102.9 pCi/L. Below the action level, 65 tests (30.5%) came in under 2 pCi/L, against 32.3% statewide, and 46 tests (21.6%) fell between 2 and 4, against 25.0% statewide.
Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 47.9% share point the same way here. USGS geology rates 74% of the county's land moderate radon potential. CDC also counts 80 tests taken after mitigation in Strafford County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2021, with 213 tests reported; the quietest, 2019, had 146.
Strafford CountyNew Hampshire, pooled
| Year | Tests | Strafford County, at or above 4 pCi/L | New Hampshire, pooled |
|---|---|---|---|
| 2018 | 153 | 43.1% | 34.6% |
| 2019 | 146 | 53.4% | 40.6% |
| 2020 | 196 | 40.8% | 40.2% |
| 2021 | 213 | 47.9% | 42.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Strafford County, Geology
The ground under Strafford County
PredictedUSGS's geologic map splits Strafford County: 73.6% of its land is moderate radon potential and 25.5% high and 0.1% low. The map puts 43.0% of Strafford County in the area it calls Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley and 23.0% in Coastal Lowlands/Eastern New England Upland, with 4 smaller areas beside them. USGS gives both a radon index of 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley | Phyllite, calcareous and aluminous schist, quartzite, slate, granofels, metavolcanic rocks. | Moderate | 10 | 43.0% |
| Coastal Lowlands/Eastern New England Upland | Late Precambrian metamorphic rocks. | Moderate | 10 | 23.0% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite and Devonian-Carboniferous two-mica granite. | High | 13 | 17.2% |
| Coastal Lowlands | Early Ordovician intrusive rocks ranging from gabbro to granodiorite. | Moderate | 10 | 7.2% |
| Eastern New England Upland | Jurassic-Cretaceous rocks of the White Mountain and New England-Quebec igneous succession. | High | 13 | 5.8% |
| Eastern New England Upland | Devonian-Carboniferous two-mica granite. | High | 13 | 2.1% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Strafford County beside the ground around it
On high-potential ground Strafford County is close to New Hampshire as a whole: 25.5% of its land against 18.8%. Of the 5 counties that border it, 2 have more high-potential ground, York County, ME the most at 99.1%.
The map rates the ground, not the air in any home.
Local help
Strafford County, Local resources
Radon testing and mitigation in Strafford 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
Strafford County, Questions
Questions about radon in Strafford County
Are radon levels high in Strafford County?
In 2021, 47.9% of the radon tests reported to CDC for Strafford County, New Hampshire were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.6 pCi/L. Of 10 New Hampshire counties with 30 or more tests for the same period, 3 reported a higher share; pooled, the state comes to 42.7%.
Which counties border Strafford County?
Strafford County borders 5 counties: York County, ME, Rockingham County, NH, Belknap County, NH, Merrimack County, NH and Carroll County, NH.
Products
Strafford County, Products
Testing a home in Strafford County
In Strafford County, 47.9% of 213 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 Strafford County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Monitor
View Plus radon and air quality monitor
- C-NRPP 2024/25: Approved
- Battery
- Wi-Fi, Bluetooth
- Screen, app
Method: Alpha spectrometry
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Strafford County, Bordering counties
Counties bordering Strafford County
Calculated by Radon411- Radon levels in Carroll County, NHEPA zone 1
54.0%at or above 4 pCi/L
Median 4.3 pCi/L · 161 tests · 6.1 points above Strafford County
- Radon levels in Rockingham County, NHEPA zone 2
48.1%at or above 4 pCi/L
Median 3.7 pCi/L · 638 tests · 0.2 points above Strafford County
- Radon levels in Belknap County, NHEPA zone 2
36.3%at or above 4 pCi/L
Median 2.6 pCi/L · 102 tests · 11.6 points below Strafford County
- Radon levels in Merrimack County, NHEPA zone 2
31.6%at or above 4 pCi/L
Median 2.2 pCi/L · 187 tests · 16.3 points below Strafford County
- Radon levels in York County, MEEPA zone 1
No CDC figure for 2021; its page reads it against its own neighbours.
Strafford County, Cities and towns
Cities and towns in Strafford County
The Census Bureau estimates 135,043 residents in Strafford County for July 1, 2025, 3,959 more than in 2020 (+3.0%). That works out to 367 people per square mile of land. Its largest town, Dover, has 34,623 residents, 25.6% of the total. Together its 3 incorporated places hold 59.6% of those residents; the other 40.4% live outside any of them. CDC's 213 reported tests for 2021 work out to 1.6 per 1,000 residents (2025 estimate), close to New Hampshire's 1.6.
From Dover to Somersworth, CDC publishes no figure by town: each reads Strafford County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Dover | 34,623 | +5.6% | 25.6% |
| Rochester | 33,716 | +3.7% | 25.0% |
| Somersworth | 12,171 | +2.0% | 9.0% |
3 incorporated places, 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).
Strafford County, Homes
Homes in Strafford County
Of Strafford County's 56,162 homes, 56% are detached houses, against 63% across New Hampshire; 18% are in buildings of five or more homes. Half of its homes were built before 1978, close to New Hampshire's 1978: 32% date from before 1960 and 22% from 2000 or later. 67% 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 | Strafford County | New Hampshire |
|---|---|---|
| Housing units | 56,162 | 644,253 |
| Detached houses | 56% | 63% |
| In buildings of 5 or more | 18% | 15% |
| Mobile homes | 8% | 5% |
| Built before 1960 | 32% | 29% |
| Built since 2000 | 22% | 18% |
| Middle year built | 1978 | 1978 |
| Owner-occupied | 67% | 73% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.