Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
Locations and reports
Radon Levels in Rockingham County, New Hampshire
EPA puts Rockingham County in Zone 2, its middle radon zone, and high results are common there: 48.1% of the 638 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
48.1%
5.4 pts above NH
- Rockingham
- 48.1%
- NH
- 42.7%
638 tests, 2021
Median result
3.7pCi/L
Below action level
- Rockingham
- 3.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2021
Tests reported
638
Most tested in NH
- 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
3 of 10
Top quarter
- Rockingham
- 48.1%
- Carroll
- 54.0%
By share, of 10 with 30+ tests
Read a result for Rockingham County
Starts at Rockingham County's median, 3.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.7 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. Rockingham County's median reported result, 2021.
The data
Rockingham County, At a glance
Rockingham County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Rockingham County is a
USGS geologic potential: Moderate across 75% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Rockingham County, 2021
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2018 | 37.7% |
| 2019 | 37.3% |
| 2020 | 41.7% |
| 2021 | 48.1% |
2021: 48.1%. Across these years the share ran from 37.3% to 48.1%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 638 tests reported to CDC for Rockingham 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).
Rockingham County, Compared
Rockingham County radon figures, compared
Calculated by Radon411In Rockingham County, about 5 in 10 reported tests in 2021 (307 of 638) were at or above EPA's action level. Against the national pool of 24.4%, the gap is 23.7 points higher. Across 10 New Hampshire counties pooled together, 42.7% of tests reached that level, so Rockingham County runs 5.4 points above its state.
Of 3 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 31.6% (Merrimack County) to 47.9% (Strafford County). By share, Rockingham County is 3rd of 10 New Hampshire counties with 30 or more tests for the same period.
Year by year, 2018 opened at 37.7% and 2021 closed at 48.1% (up 10.4 points), with 2021 the high at 48.1%. Half the tests came in under 3.7 pCi/L and half over it; the single highest reached 91.8 pCi/L. Below the action level, 183 tests (28.7%) came in under 2 pCi/L, against 32.3% statewide, and 148 tests (23.2%) 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 48.1% share point the same way here. USGS geology rates 75% of the county's land moderate radon potential. CDC also counts 203 tests taken after mitigation in Rockingham County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2019, with 797 tests reported; the quietest, 2021, had 638.
Rockingham CountyNew Hampshire, pooled
| Year | Tests | Rockingham County, at or above 4 pCi/L | New Hampshire, pooled |
|---|---|---|---|
| 2018 | 690 | 37.7% | 34.6% |
| 2019 | 797 | 37.3% | 40.6% |
| 2020 | 674 | 41.7% | 40.2% |
| 2021 | 638 | 48.1% | 42.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Rockingham County, Geology
The ground under Rockingham County
PredictedMost of the ground under Rockingham County is one class on USGS's geologic map: 75.0% of its land is moderate radon potential, with 23.0% high. The map puts 67.7% of Rockingham County in the area it calls Coastal Lowlands/Eastern New England Upland and 21.1% 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 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Coastal Lowlands/Eastern New England Upland | Late Precambrian metamorphic rocks. | Moderate | 10 | 67.7% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite and Devonian-Carboniferous two-mica granite. | High | 13 | 21.1% |
| Coastal Lowlands | Early Ordovician intrusive rocks ranging from gabbro to granodiorite. | Moderate | 10 | 3.8% |
| Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley | Phyllite, calcareous and aluminous schist, quartzite, slate, granofels, metavolcanic rocks. | Moderate | 10 | 2.0% |
| Eastern New England Upland | Devonian-Carboniferous two-mica granite. | High | 13 | 1.3% |
| Coastal Lowlands | Precambrian-Carboniferous schist, phyllite, slate, gneiss, metavolcanic rocks, granite | Moderate | 10 | 1.2% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Rockingham County beside the ground around it
On high-potential ground Rockingham County is close to New Hampshire as a whole: 23.0% of its land against 18.8%. Of the 5 counties that border it, 3 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
Rockingham County, Local resources
Radon testing and mitigation in Rockingham 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
Rockingham County, Questions
Questions about radon in Rockingham County
Are radon levels high in Rockingham County?
In 2021, 48.1% of the radon tests reported to CDC for Rockingham County, New Hampshire were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.7 pCi/L. Of 10 New Hampshire counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 42.7%.
Which counties border Rockingham County?
Rockingham County borders 5 counties: Strafford County, NH, Essex County, MA, Hillsborough County, NH, York County, ME and Merrimack County, NH.
Products
Rockingham County, Products
Testing a home in Rockingham County
In Rockingham County, 48.1% of 638 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 Rockingham 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
RadonScan USB-powered radon monitor with a color screen
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
First reading: Within 5 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Rockingham County, Bordering counties
Counties bordering Rockingham County
Calculated by Radon411- Radon levels in Strafford County, NHEPA zone 2
47.9%at or above 4 pCi/L
Median 3.6 pCi/L · 213 tests · 0.2 points below Rockingham County
- Radon levels in Hillsborough County, NHEPA zone 2
41.5%at or above 4 pCi/L
Median 3.2 pCi/L · 610 tests · 6.6 points below Rockingham County
- Radon levels in Merrimack County, NHEPA zone 2
31.6%at or above 4 pCi/L
Median 2.2 pCi/L · 187 tests · 16.5 points below Rockingham County
- Radon levels in Essex County, MAEPA zone 1
No CDC figure for 2021; its page reads it against its own neighbours.
- Radon levels in York County, MEEPA zone 1
No CDC figure for 2021; its page reads it against its own neighbours.
Rockingham County, Cities and towns
Cities and towns in Rockingham County
The Census Bureau estimates 324,077 residents in Rockingham County for July 1, 2025, 9,444 more than in 2020 (+3.0%). That works out to 466 people per square mile of land. Portsmouth, its one incorporated place, has 23,028 residents, 7.1% of the total. CDC's 638 reported tests for 2021 work out to 2.0 per 1,000 residents (2025 estimate), close to New Hampshire's 1.6.
Portsmouth is the one incorporated place here; CDC publishes no figure by town, so it reads Rockingham County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Portsmouth | 23,028 | +4.7% | 7.1% |
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).
Rockingham County, Homes
Homes in Rockingham County
Of Rockingham County's 136,681 homes, 65% are detached houses, against 63% across New Hampshire; 15% are in buildings of five or more homes. Half of its homes were built before 1982, close to New Hampshire's 1978: 23% date from before 1960 and 22% from 2000 or later. Owners live in 79% of the occupied homes (New Hampshire: 73%), so for most households a test and a fix are their own to order.
| Homes | Rockingham County | New Hampshire |
|---|---|---|
| Housing units | 136,681 | 644,253 |
| Detached houses | 65% | 63% |
| In buildings of 5 or more | 15% | 15% |
| Mobile homes | 5% | 5% |
| Built before 1960 | 23% | 29% |
| Built since 2000 | 22% | 18% |
| Middle year built | 1982 | 1978 |
| Owner-occupied | 79% | 73% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.