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 Merrimack County, New Hampshire
EPA puts Merrimack County in Zone 2, its middle radon zone, and 31.6% of its 187 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
31.6%
11.1 pts below NH
- Merrimack
- 31.6%
- NH
- 42.7%
187 tests, 2021
Median result
2.2pCi/L
Below action level
- Merrimack
- 2.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2021
Tests reported
187
4th of 10 by tests
- Merrimack
- 187
- 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
8 of 10
Middle half
- Merrimack
- 31.6%
- Carroll
- 54.0%
By share, of 10 with 30+ tests
Read a result for Merrimack County
Starts at Merrimack County's median, 2.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.2 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. Merrimack County's median reported result, 2021.
The data
Merrimack County, At a glance
Merrimack County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Merrimack County is a
USGS geologic potential: Moderate across 52% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Merrimack County, 2021
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2018 | 40.9% |
| 2019 | 47.7% |
| 2020 | 32.9% |
| 2021 | 31.6% |
2021: 31.6%. Across these years the share ran from 31.6% to 47.7%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 187 tests reported to CDC for Merrimack 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).
Merrimack County, Compared
Merrimack County radon figures, compared
Calculated by Radon411In Merrimack County, about 3 in 10 reported tests in 2021 (59 of 187) were at or above EPA's action level. Against the national pool of 24.4%, the gap is 7.2 points higher. Across 10 New Hampshire counties pooled together, 42.7% of tests reached that level, so Merrimack County runs 11.1 points below its state.
Of 6 neighbours with a figure, 5 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 23.3% (Sullivan County) to 48.1% (Rockingham County). By share, Merrimack County is 8th of 10 New Hampshire counties with 30 or more tests for the same period.
Year by year, 2018 opened at 40.9% and 2021 closed at 31.6% (down 9.3 points), with 2019 the high at 47.7%. Half the tests came in under 2.2 pCi/L and half over it; the single highest reached 65.9 pCi/L. Below the action level, 86 tests (46.0%) came in under 2 pCi/L, against 32.3% statewide, and 42 tests (22.5%) 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 31.6% share point the same way here. USGS geology rates 52% of the county's land moderate radon potential. CDC also counts 20 tests taken after mitigation in Merrimack County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2019, with 285 tests reported; the quietest, 2018, had 154.
Merrimack CountyNew Hampshire, pooled
31.6% % of tests42.7% % of tests
| Year | Tests | Merrimack County, at or above 4 pCi/L | New Hampshire, pooled |
|---|---|---|---|
| 2018 | 154 | 40.9% | 34.6% |
| 2019 | 285 | 47.7% | 40.6% |
| 2020 | 155 | 32.9% | 40.2% |
| 2021 | 187 | 31.6% | 42.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Merrimack County, Geology
The ground under Merrimack County
PredictedUSGS's geologic map splits Merrimack County: 51.8% of its land is moderate radon potential and 14.8% high and 33.4% low. The map puts 47.0% of Merrimack County in the area it calls Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley and 33.4% in Eastern New England Upland, with 5 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 |
|---|---|---|---|---|
| Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley | Phyllite, calcareous and aluminous schist, quartzite, slate, granofels, metavolcanic rocks. | Moderate | 10 | 47.0% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite. | Low | 8 | 33.4% |
| Eastern New England Upland | Devonian-Carboniferous two-mica granite. | High | 13 | 8.8% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite and Devonian-Carboniferous two-mica granite. | High | 13 | 5.5% |
| Eastern New England Upland | Late Cambrian-Early Devonian limestone, conglomerate, phyllite, schist, slate. | Moderate | 10 | 3.8% |
| Eastern New England Upland | Silurian-Devonian intrusive rocks ranging from gabbro to granite. | Moderate | 10 | 0.9% |
One smaller area is not listed. Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Merrimack County beside the ground around it
On high-potential ground Merrimack County is close to New Hampshire as a whole: 14.8% of its land against 18.8%. Of the 6 counties that border it, 4 have more high-potential ground, Strafford County the most at 25.5%.
The map rates the ground, not the air in any home.
Local help
Merrimack County, Local resources
Radon testing and mitigation in Merrimack 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
Merrimack County, Questions
Questions about radon in Merrimack County
Are radon levels high in Merrimack County?
In 2021, 31.6% of the radon tests reported to CDC for Merrimack County, New Hampshire were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.2 pCi/L. Of 10 New Hampshire counties with 30 or more tests for the same period, 7 reported a higher share; pooled, the state comes to 42.7%.
Which counties border Merrimack County?
Merrimack County borders 6 counties: Belknap County, Hillsborough County, Sullivan County, Strafford County, Rockingham County and Grafton County.
Products
Merrimack County, Products
Testing a home in Merrimack County
In Merrimack County, 31.6% of 187 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 Merrimack 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
EcoQube Flex battery digital radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Alarm
- Screen, app
Method: Ion chamber
First reading: Within 15 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Merrimack County, Bordering counties
Counties bordering Merrimack County
Calculated by Radon411- Radon levels in Rockingham CountyEPA zone 2
48.1%at or above 4 pCi/L
Median 3.7 pCi/L · 638 tests · 16.5 points above Merrimack County
- Radon levels in Strafford CountyEPA zone 2
47.9%at or above 4 pCi/L
Median 3.6 pCi/L · 213 tests · 16.3 points above Merrimack County
- Radon levels in Grafton CountyEPA zone 2
44.4%at or above 4 pCi/L
Median 3.0 pCi/L · 142 tests · 12.8 points above Merrimack County
- Radon levels in Hillsborough CountyEPA zone 2
41.5%at or above 4 pCi/L
Median 3.2 pCi/L · 610 tests · 9.9 points above Merrimack County
- Radon levels in Belknap CountyEPA zone 2
36.3%at or above 4 pCi/L
Median 2.6 pCi/L · 102 tests · 4.7 points above Merrimack County
- Radon levels in Sullivan CountyEPA zone 2
23.3%at or above 4 pCi/L
Median 2.7 pCi/L · 60 tests · 8.3 points below Merrimack County
Merrimack County, Cities and towns
Cities and towns in Merrimack County
The Census Bureau estimates 158,078 residents in Merrimack County for July 1, 2025, 4,017 more than in 2020 (+2.6%). That works out to 169 people per square mile of land. Its largest town, Concord, has 44,597 residents, 28.2% of the total. Together its 2 incorporated places hold 33.8% of those residents; the other 66.2% live outside any of them. CDC's 187 reported tests for 2021 work out to 1.2 per 1,000 residents (2025 estimate), close to New Hampshire's 1.6.
From Concord to Franklin, CDC publishes no figure by town: each reads Merrimack County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Concord | 44,597 | +1.2% | 28.2% |
| Franklin | 8,839 | +1.1% | 5.6% |
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).
Merrimack County, Homes
Homes in Merrimack County
Of Merrimack County's 66,080 homes, 63% are detached houses, against 63% across New Hampshire; 14% are in buildings of five or more homes. Half of its homes were built before 1977, close to New Hampshire's 1978: 33% date from before 1960 and 18% from 2000 or later. 73% 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 | Merrimack County | New Hampshire |
|---|---|---|
| Housing units | 66,080 | 644,253 |
| Detached houses | 63% | 63% |
| In buildings of 5 or more | 14% | 15% |
| Mobile homes | 7% | 5% |
| Built before 1960 | 33% | 29% |
| Built since 2000 | 18% | 18% |
| Middle year built | 1977 | 1978 |
| Owner-occupied | 73% | 73% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.