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Radon Levels in Grafton County, New Hampshire

EPA puts Grafton County in Zone 2, its middle radon zone, and high results are common there: 44.4% of the 142 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

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  • Share at 4+ pCi/L

    44.4%

    1.7 pts above NH

    Grafton
    44.4%
    NH
    42.7%

    142 tests, 2021

  • Median result

    3.0pCi/L

    Below action level

    Grafton
    3.0 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2021

  • Tests reported

    142

    6th of 10 by tests

    Grafton
    142
    Rockingham
    638

    Reported to CDC before any fix, 2021

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in NH

    5 of 10

    Middle half

    Grafton
    44.4%
    Carroll
    54.0%

    By share, of 10 with 30+ tests

Read a result for Grafton County

Starts at Grafton County's median, 3.0 pCi/L

3.0pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 3.0 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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. Grafton County's median reported result, 2021.

Interpret this readingWhat a fix costs

The data

Grafton County, At a glance

Grafton County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Grafton County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 79% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Grafton County, 2021

Share of reported tests at or above 4 pCi/L, by year, Grafton County
Share of reported tests at or above 4 pCi/L, by year, Grafton County
YearShare of reported tests at or above 4 pCi/L
201829.9%
201939.1%
202032.0%
202144.4%

2021: 44.4%. Across these years the share ran from 29.9% to 44.4%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 142 tests reported to CDC for Grafton 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).

How to read these figures

Grafton County, Compared

Grafton County radon figures, compared

Calculated by Radon411

In Grafton County, about 4 in 10 reported tests in 2021 (63 of 142) were at or above EPA's action level. Against the national pool of 24.4%, the gap is 20.0 points higher. Across 10 New Hampshire counties pooled together, 42.7% of tests reached that level, so Grafton County runs 1.7 points above its state.

Of 8 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 6 a smaller one; the spread is 18.3% (Windsor County, VT) to 54.0% (Carroll County). By share, Grafton County is 5th of 10 New Hampshire counties with 30 or more tests for the same period.

Year by year, 2018 opened at 29.9% and 2021 closed at 44.4% (up 14.5 points), with 2021 the high at 44.4%. Half the tests came in under 3.0 pCi/L and half over it; the single highest reached 53.9 pCi/L. Below the action level, 48 tests (33.8%) came in under 2 pCi/L, against 32.3% statewide, and 31 tests (21.8%) 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 44.4% share point the same way here. USGS geology rates 79% of the county's land moderate radon potential. CDC also counts 40 tests taken after mitigation in Grafton County for the same period: tests in homes where a fix was already in.

The busiest year on file was 2019, with 284 tests reported; the quietest, 2021, had 142.

Share of reported tests at or above 4 pCi/L by year, Grafton County against New Hampshire2018 to 2021, years with 30 or more tests: Grafton County 29.9% to 44.4%, the state's pooled share 42.7% in 2021.
Grafton CountyNew Hampshire, pooled
Share of reported tests at or above 4 pCi/L by year, Grafton County against New Hampshire: data table
YearTestsGrafton County, at or above 4 pCi/LNew Hampshire, pooled
201820129.9%34.6%
201928439.1%40.6%
202022232.0%40.2%
202114244.4%42.7%
Grafton County against New Hampshire, the United States and nearby counties, 2021
AreaTestsAt or above 4 pCi/LMedianDifference from Grafton County
Grafton County14244.4%3.0 pCi/LThis county
New Hampshire, pooled10 counties, pooled2,26042.7%Not pooled−1.7 points
United States, pooled807 counties, pooled344,60424.4%Not pooled−20.0 points
Rockingham Countyhighest in the state63848.1%3.7 pCi/L+3.7 points
Cheshire Countylowest in the state10319.4%2.1 pCi/L−25.0 points
Carroll County, NHborders it16154.0%4.3 pCi/L+9.6 points
Coos County, NHborders it4452.3%4.3 pCi/L+7.9 points
Belknap County, NHborders it10236.3%2.6 pCi/L−8.1 points
Essex County, VTborders it1833.3%2.5 pCi/L−11.1 points
Merrimack County, NHborders it18731.6%2.2 pCi/L−12.8 points
Orange County, VTborders it7529.3%2.1 pCi/L−15.1 points
Caledonia County, VTborders it9526.3%1.8 pCi/L−18.1 points
Sullivan County, NHborders it6023.3%2.7 pCi/L−21.1 points
Windsor County, VTborders it17518.3%1.6 pCi/L−26.1 points
Where Grafton County's reported results fell, 2021, beside New Hampshire and the United States
ResultGrafton County testsGrafton County shareNew Hampshire shareU.S. shareAgainst New Hampshire
Under 2 pCi/L4833.8%32.3%54.4%+1.5 points
2 to 4 pCi/L3121.8%25.0%21.2%−3.2 points
4 pCi/L and above6344.4%42.7%24.4%+1.7 points
Grafton County ranked among the 10 New Hampshire counties with 30 or more tests, by share at or above 4 pCi/L, 2021
CountyRankTestsAt or above 4 pCi/LMedian
Carroll County1 of 1016154.0%4.3 pCi/L
Coos County2 of 104452.3%4.3 pCi/L
Rockingham County3 of 1063848.1%3.7 pCi/L
Strafford County4 of 1021347.9%3.6 pCi/L
Grafton County5 of 1014244.4%3.0 pCi/L
Hillsborough County6 of 1061041.5%3.2 pCi/L
Belknap County7 of 1010236.3%2.6 pCi/L
Merrimack County8 of 1018731.6%2.2 pCi/L
Sullivan County9 of 106023.3%2.7 pCi/L
Cheshire County10 of 1010319.4%2.1 pCi/L
Grafton County radon tests by year, against New Hampshire's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNew Hampshire, pooledChange from the row before
202114244.4%3.0 pCi/L53.9 pCi/L42.7%+12.4 points
202022232.0%2.3 pCi/L170.5 pCi/L40.2%−7.1 points
201928439.1%2.6 pCi/L97.1 pCi/L40.6%+9.2 points
201820129.9%2.4 pCi/L78.4 pCi/L34.6%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Grafton County, Geology

The ground under Grafton County

Predicted

Most of the ground under Grafton County is one class on USGS's geologic map: 78.8% of its land is moderate radon potential, with 17.7% high and 3.5% low. The map puts 36.2% of Grafton County in the area it calls Eastern New England Upland and 18.4% in Parts of Central Lowlands, Eastern New England Upland and Merrimack Valley, with 11 smaller areas beside them. USGS gives both a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under Grafton County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Eastern New England UplandLate Cambrian-Early Devonian limestone, conglomerate, phyllite, schist, slate.Moderate1036.2%
Parts of Central Lowlands, Eastern New England Upland and Merrimack ValleyPhyllite, calcareous and aluminous schist, quartzite, slate, granofels, metavolcanic rocks.Moderate1018.4%
White MountainsJurassic-Cretaceous rocks of the White Mountain and New England-Quebec igneous succession.High1312.3%
Eastern New England UplandMiddle to Late Ordovician intrusive rocks ranging from gabbro to syenite.Moderate108.0%
Eastern New England Upland/White MountainsSilurian-Devonian intrusive rocks ranging from gabbro to granite.Moderate106.5%
Eastern New England UplandDevonian-Carboniferous two-mica granite.High134.1%

7 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.

Grafton County beside the ground around it

On high-potential ground Grafton County is close to New Hampshire as a whole: 17.7% of its land against 18.8%. Of the 9 counties that border it, 1 has more high-potential ground, Carroll County the most at 45.9%.

Share of land by USGS radon potential: Grafton County, the 9 counties bordering it and New Hampshire
AreaEPA zoneLow potentialModerate potentialHigh potential
Grafton CountyZone 23.5%78.8%17.7%
Carroll CountyZone 116.2%38.0%45.9%
Belknap CountyZone 217.7%71.8%10.5%
Orange County, VTZone 2None100%None
Caledonia County, VTZone 2None100%None
Merrimack CountyZone 233.4%51.8%14.8%
Windsor County, VTZone 2None100%None
Sullivan CountyZone 210.7%88.2%1.1%
Essex County, VTZone 2None100%None
Coos CountyZone 2None83.7%16.3%
New Hampshire10 counties, pooled by land areaVaries9.6%71.4%18.8%

The map rates the ground, not the air in any home.

Local help

Grafton County, Local resources

Radon testing and mitigation in Grafton County

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

Grafton County, Questions

Questions about radon in Grafton County

Are radon levels high in Grafton County?

In 2021, 44.4% of the radon tests reported to CDC for Grafton County, New Hampshire were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.0 pCi/L. Of 10 New Hampshire counties with 30 or more tests for the same period, 4 reported a higher share; pooled, the state comes to 42.7%.

Which counties border Grafton County?

Grafton County borders 9 counties: Carroll County, NH, Belknap County, NH, Orange County, VT, Caledonia County, VT, Merrimack County, NH, Windsor County, VT, Sullivan County, NH, Essex County, VT and Coos County, NH.

Products

Grafton County, Products

Testing a home in Grafton County

In Grafton County, 44.4% of 142 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 Grafton County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Grafton County homes, compared

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Grafton County, Bordering counties

Counties bordering Grafton County

Calculated by Radon411

Grafton County, Cities and towns

Cities and towns in Grafton County

The Census Bureau estimates 93,225 residents in Grafton County for July 1, 2025, 2,032 more than in 2020 (+2.2%). That works out to 55 people per square mile of land. Lebanon, its one incorporated place, has 15,481 residents, 16.6% of the total. CDC's 142 reported tests for 2021 work out to 1.5 per 1,000 residents (2025 estimate), close to New Hampshire's 1.6.

Lebanon is the one incorporated place here; CDC publishes no figure by town, so it reads Grafton County's.

Lebanon, Grafton County: residents on July 1, 2025
PlaceResidentsSince 2020Share of residents
Lebanon15,481+8.2%16.6%

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).

Grafton County, Homes

Homes in Grafton County

Of Grafton County's 51,478 homes, 61% are detached houses, against 63% across New Hampshire; 16% are in buildings of five or more homes. Half of its homes were built before 1980, close to New Hampshire's 1978: 29% date from before 1960 and 19% from 2000 or later. 71% 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 in Grafton County, New Hampshire, 2019 to 2023
HomesGrafton CountyNew Hampshire
Housing units51,478644,253
Detached houses61%63%
In buildings of 5 or more16%15%
Mobile homes7%5%
Built before 196029%29%
Built since 200019%18%
Middle year built19801978
Owner-occupied71%73%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.