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 Hillsborough County, New Hampshire
EPA puts Hillsborough County in Zone 2, its middle radon zone, and high results are common there: 41.5% of the 610 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
41.5%
1.2 pts below NH
- Hillsborough
- 41.5%
- NH
- 42.7%
610 tests, 2021
Median result
3.2pCi/L
Below action level
- Hillsborough
- 3.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2021
Tests reported
610
2nd of 10 by tests
- Hillsborough
- 610
- 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
6 of 10
Middle half
- Hillsborough
- 41.5%
- Carroll
- 54.0%
By share, of 10 with 30+ tests
Read a result for Hillsborough County
Starts at Hillsborough County's median, 3.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.2 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. Hillsborough County's median reported result, 2021.
The data
Hillsborough County, At a glance
Hillsborough County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Hillsborough County is a
USGS geologic potential: Moderate across 62% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Hillsborough County, 2021
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2018 | 32.1% |
| 2019 | 40.0% |
| 2020 | 44.3% |
| 2021 | 41.5% |
2021: 41.5%. Across these years the share ran from 32.1% to 44.3%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 610 tests reported to CDC for Hillsborough 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).
Hillsborough County, Compared
Hillsborough County radon figures, compared
Calculated by Radon411In Hillsborough County, about 4 in 10 reported tests in 2021 (253 of 610) were at or above EPA's action level. Against the national pool of 24.4%, the gap is 17.1 points higher. Across 10 New Hampshire counties pooled together, 42.7% of tests reached that level, so Hillsborough County runs 1.2 points below its state.
Of 4 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 19.4% (Cheshire County) to 48.1% (Rockingham County). By share, Hillsborough County is 6th of 10 New Hampshire counties with 30 or more tests for the same period.
Year by year, 2018 opened at 32.1% and 2021 closed at 41.5% (up 9.4 points), with 2020 the high at 44.3%. Half the tests came in under 3.2 pCi/L and half over it; the single highest reached 63.9 pCi/L. Below the action level, 198 tests (32.5%) came in under 2 pCi/L, against 32.3% statewide, and 159 tests (26.1%) 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 41.5% share point the same way here. USGS geology rates 62% of the county's land moderate radon potential. CDC also counts 102 tests taken after mitigation in Hillsborough County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2018, with 675 tests reported; the quietest, 2020, had 562.
Hillsborough CountyNew Hampshire, pooled
| Year | Tests | Hillsborough County, at or above 4 pCi/L | New Hampshire, pooled |
|---|---|---|---|
| 2018 | 675 | 32.1% | 34.6% |
| 2019 | 655 | 40.0% | 40.6% |
| 2020 | 562 | 44.3% | 40.2% |
| 2021 | 610 | 41.5% | 42.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Hillsborough County, Geology
The ground under Hillsborough County
PredictedUSGS's geologic map splits Hillsborough County: 61.7% of its land is moderate radon potential and 20.4% high and 17.8% low. The map puts 21.2% of Hillsborough County in the area it calls Eastern New England Upland and 18.2% in Eastern New England Upland, with 8 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 |
|---|---|---|---|---|
| Eastern New England Upland | Late Cambrian-Early Devonian limestone, conglomerate, phyllite, schist, slate. | Moderate | 10 | 21.2% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite and Devonian-Carboniferous two-mica granite. | High | 13 | 18.2% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite. | Low | 8 | 17.8% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite. | Moderate | 10 | 15.7% |
| Coastal Lowlands/Eastern New England Upland | Late Precambrian metamorphic rocks. | Moderate | 10 | 13.8% |
| Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley | Phyllite, calcareous and aluminous schist, quartzite, slate, granofels, metavolcanic rocks. | Moderate | 10 | 5.2% |
4 smaller areas are not listed. Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Hillsborough County beside the ground around it
On high-potential ground Hillsborough County is close to New Hampshire as a whole: 20.4% of its land against 18.8%. Of the 7 counties that border it, 4 have more high-potential ground, Essex County, MA the most at 86.7%.
The map rates the ground, not the air in any home.
Local help
Hillsborough County, Local resources
Radon testing and mitigation in Hillsborough 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
Hillsborough County, Questions
Questions about radon in Hillsborough County
Are radon levels high in Hillsborough County?
In 2021, 41.5% of the radon tests reported to CDC for Hillsborough County, New Hampshire were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.2 pCi/L. Of 10 New Hampshire counties with 30 or more tests for the same period, 5 reported a higher share; pooled, the state comes to 42.7%.
Which counties border Hillsborough County?
Hillsborough County borders 7 counties: Merrimack County, NH, Cheshire County, NH, Rockingham County, NH, Sullivan County, NH, Middlesex County, MA, Worcester County, MA and Essex County, MA.
Products
Hillsborough County, Products
Testing a home in Hillsborough County
In Hillsborough County, 41.5% of 610 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 Hillsborough 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
Monitor
RadonScan-Plus USB-powered radon monitor with Wi-Fi
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Hillsborough County, Bordering counties
Counties bordering Hillsborough County
Calculated by Radon411- Radon levels in Rockingham County, NHEPA zone 2
48.1%at or above 4 pCi/L
Median 3.7 pCi/L · 638 tests · 6.6 points above Hillsborough County
- Radon levels in Merrimack County, NHEPA zone 2
31.6%at or above 4 pCi/L
Median 2.2 pCi/L · 187 tests · 9.9 points below Hillsborough County
- Radon levels in Sullivan County, NHEPA zone 2
23.3%at or above 4 pCi/L
Median 2.7 pCi/L · 60 tests · 18.2 points below Hillsborough County
- Radon levels in Cheshire County, NHEPA zone 2
19.4%at or above 4 pCi/L
Median 2.1 pCi/L · 103 tests · 22.1 points below Hillsborough County
- Radon levels in Middlesex County, MAEPA zone 1
No CDC figure for 2021; its page reads it against its own neighbours.
- Radon levels in Worcester County, MAEPA zone 1
No CDC figure for 2021; its page reads it against its own neighbours.
- Radon levels in Essex County, MAEPA zone 1
No CDC figure for 2021; its page reads it against its own neighbours.
Hillsborough County, Cities and towns
Cities and towns in Hillsborough County
The Census Bureau estimates 433,415 residents in Hillsborough County for July 1, 2025, 10,513 more than in 2020 (+2.5%). That works out to 494 people per square mile of land. Its largest town, Manchester, has 116,818 residents, 27.0% of the total. Together its 2 incorporated places hold 48.3% of those residents; the other 51.7% live outside any of them. CDC's 610 reported tests for 2021 work out to 1.4 per 1,000 residents (2025 estimate), close to New Hampshire's 1.6.
From Manchester to Nashua, CDC publishes no figure by town: each reads Hillsborough County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Manchester | 116,818 | +1.1% | 27.0% |
| Nashua | 92,435 | +1.4% | 21.3% |
Places in Hillsborough County with a city page: 1 of 1
2 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).
Hillsborough County, Homes
Homes in Hillsborough County
Of Hillsborough County's 176,753 homes, 57% are detached houses, against 63% across New Hampshire; 21% are in buildings of five or more homes. Half of its homes were built before 1977, close to New Hampshire's 1978: 29% date from before 1960 and 15% from 2000 or later. 68% 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 | Hillsborough County | New Hampshire |
|---|---|---|
| Housing units | 176,753 | 644,253 |
| Detached houses | 57% | 63% |
| In buildings of 5 or more | 21% | 15% |
| Mobile homes | 2% | 5% |
| Built before 1960 | 29% | 29% |
| Built since 2000 | 15% | 18% |
| Middle year built | 1977 | 1978 |
| Owner-occupied | 68% | 73% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.