Locations and reports
Radon Levels in Carroll County, New Hampshire
What this means for you
- Your area: EPA rates Carroll County Zone 1, the highest of its three radon zones. That is a prediction for the whole county, and homes with elevated levels occur in all three zones.
- Local tests: Of 161 radon tests reported to CDC for Carroll County (2021), 54.0% were at or above 4 pCi/L, EPA's action level.
- Your home: The only way to know your home’s level is to test it.
pCi/L (picocuries per liter) is the unit radon is measured in. EPA recommends fixing a home at 4 pCi/L or above, its action level.
In 2021, 54.0% of the radon tests reported to CDC for Carroll County, New Hampshire came back at or above the EPA action level of 4 pCi/L, and the median result was 4.3 pCi/L. EPA's Map of Radon Zones places the county in Zone 1, highest predicted potential. Radon levels vary from home to home, so only a test measures the level in yours.
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county as a whole.
This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.
USGS geologic potential: Low across 46% of the county's land area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Carroll County, 2021
- Tests reported
- 161
- At or above 4 pCi/L
- 54.0%
- Median result
- 4.3 pCi/L
Of 161 pre-mitigation tests reported to CDC, not homes in this area. CDC publishes the share in each band, not a count per band, so the per-band counts in the table are calculated by Radon411 and rounded to add up to the published total.
| Result band | Tests Calculated by Radon411 | Share Measured |
|---|---|---|
| Under 2 pCi/L | 30 | 18.6% |
| 2 to 4 pCi/L | 44 | 27.3% |
| 4 pCi/L and above | 87 | 54.0% |
Distribution of tested buildings, not this house. People testing before a sale, or because they suspect a problem, are over-represented in any reported testing data.
Measured: CDC tracking data. Figure above: 2021. Measured data period: 2005 to 2021 (every CDC figure on file).
Carroll County, In figures
Carroll County in figures
What the published data says about Carroll County, in words. A zone and a share of tests describe an area, never the level in any one home.
Predicted
PredictedEPA places Carroll County in Zone 1, highest predicted potential, as it does 0 other counties of New Hampshire's 10.
Of the 6 bordering counties, EPA places Oxford County and York County in Zone 1 and Belknap County, Coos County, Grafton County and Strafford County in Zone 2.
Reported tests
MeasuredCDC has annual figures for Carroll County for 4 years, 2018 to 2021. In 2021, 54.0% of 161 reported tests were at or above 4 pCi/L.
Across those years the share ranged from 48.5% (2018) to 54.2% (2019). Few tests in a year can move it a long way.
New Hampshire's radon program is the New Hampshire Radon Program, run by New Hampshire Department of Health and Human Services; its contacts are under Local resources.
Carroll County, Reported testing
Reported testing over time
Measured| Year | Median reported result | Highest reported result | Share of tests at or above 4 pCi/L |
|---|---|---|---|
| 2018 | 3.9 pCi/L | 73.7 pCi/L | 48.5% |
| 2019 | 4.2 pCi/L | 214.9 pCi/L | 54.2% |
| 2020 | 4.1 pCi/L | 417.9 pCi/L | 52.3% |
| 2021 | 4.3 pCi/L | 345.3 pCi/L | 54.0% |
What these figures count
Every percentage here is a share of radon tests reported to CDC for Carroll County in 2021. It is not a share of homes in Carroll County, and it is not a random sample: it counts only the tests people chose to run and that were reported.
The shares and the median are calculated from pre-mitigation tests (161 for 2021). CDC also reports the number of buildings tested (178), a different count, so the two totals are not interchangeable.
Carroll County, Comparison
How Carroll County compares
MeasuredCarroll County's own published CDC figures beside those of the counties that border it, for the same period.
Share of reported tests at or above 4 pCi/L
Measured2021, highest first. Each county’s own published CDC figure.
- Carroll CountyThis page161 tests54.0%
- Coos CountyNH44 tests52.3%
- Strafford CountyNH213 tests47.9%
- Grafton CountyNH142 tests44.4%
- Belknap CountyNH102 tests36.3%
Median reported result
Measured2021, highest first. Each county’s own published CDC figure.
- Carroll CountyThis page161 tests4.3 pCi/L
- Coos CountyNH44 tests4.3 pCi/L
- Strafford CountyNH213 tests3.6 pCi/L
- Grafton CountyNH142 tests3.0 pCi/L
- Belknap CountyNH102 tests2.6 pCi/L
Each figure is that county’s own published CDC figure for 2021, counting radon tests reported to CDC, not homes. Carroll County is this page. Nothing is averaged or combined across counties. The test count beside each county is CDC’s published number of pre-mitigation tests behind its figures. Figures from few tests can swing widely from year to year. No published CDC figure for 2021: York County, ME; Oxford County, ME. Every New Hampshire county’s own figure is in the New Hampshire county table.
CDC publishes this figure only for counties here, so there is no state or national number to compare Carroll County, New Hampshire with.
Carroll County, Bordering counties
Counties bordering Carroll County
Calculated by Radon4116 counties share a boundary with Carroll County, computed from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county’s report can be worth reading alongside this one.
- Belknap CountyNHZone 2: Moderate predicted potential
- Grafton CountyNHZone 2: Moderate predicted potential
- Strafford CountyNHZone 2: Moderate predicted potential
- York CountyMEZone 1: Highest predicted potential
- Oxford CountyMEZone 1: Highest predicted potential
- Coos CountyNHZone 2: Moderate predicted potential
Carroll County, Local resources
Local resources in New Hampshire
Who to ask in New Hampshire: the state's radon program, test kits and professionals.
New Hampshire Radon Program
New Hampshire Department of Health and Human Services
New Hampshire’s radon program answers questions about testing, mitigation and the rules where you live.
- 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.
Test kits
The program says: The NH Radon Program provides free radon test kits to NH residents.
Radon professionals
No professionals are listed in New Hampshire yet. The state program can point you to registered testers and mitigators.
See the New Hampshire directoryCarroll County, Questions
Questions about radon in Carroll County
Common questions8 questions, answered from the figures above
Are radon levels high in Carroll County?
In 2021, 54.0% of the radon tests reported to CDC for Carroll County, New Hampshire were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.3 pCi/L. That is a share of reported tests, not of homes. EPA places Carroll County in Zone 1, highest predicted potential, a predicted average indoor screening level greater than 4 pCi/L. Homes with elevated levels occur in all three zones, so the figures describe the area, not your house. Testing is the only way to know the radon level in a specific building.
How do I get a radon test in Carroll County?
EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. No certified tester listed on Radon411 names Carroll County as a service area yet. The New Hampshire radon program is the place to ask about certified testers and any test kit offer it runs.
How to test a homeTest kits comparedFree and low-cost kits by stateNew Hampshire radon program
Who does radon mitigation in Carroll County?
Radon411 has no certified mitigators listed for New Hampshire yet. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional. Your state radon program is the place to check whether New Hampshire requires one.
How radon mitigation worksWhat mitigation costsNew Hampshire radon program
What EPA radon zone is Carroll County in?
EPA places Carroll County, New Hampshire in Zone 1, which EPA describes as highest predicted potential for the area. A zone is a prediction for the whole county and never determines whether a particular home should be tested. EPA recommends testing every home regardless of zone.
Should I test my home in Carroll County?
Yes. Testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. How to test a home.
When is the best time of year to test?
EPA says short-term tests stay in the home from 2 to 90 days and that all radon tests should run a minimum of 48 hours; long-term tests stay more than 90 days. EPA's guides do not name a best season: they say radon levels tend to vary from day to day and season to season, so a long-term test is more likely than a short-term test to tell you the year-round average.
What does it cost to test?
EPA's Citizen's Guide calls testing easy and inexpensive, and EPA's Home Buyer's and Seller's Guide says passive short-term and long-term devices are generally inexpensive, while active devices may cost more. No national average price is published for this, so Radon411 does not give one. What testing costs.
Which counties border Carroll County?
Carroll County borders 6 counties, derived from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county's report can be relevant.
What these figures mean if you own, buy, sell or rent
The reported-test figures on this page describe Carroll County, New Hampshire in 2021. They describe tests other people carried out in other buildings, and none of them measures yours.
- How to test a home
If you own your home
Test the lowest lived-in level; a short-term kit screens in days, a long-term kit reflects the year.
- Buying a house: radon guide
If you are buying
Ask for past results and any system's post-mitigation test, and test during the sale.
- Selling a house: radon guide
If you are selling
Testing before you list puts the timing in your hands; disclosure rules differ by state.
- Radon in rental homes
If you rent, or rent out a home
A tenant can test; a fix is the owner's to make, and duties differ by state.
How long a test has to run, under what conditions, and what EPA says a result means: the testing standard, in full.
Carroll County, Products
Testing and mitigation products
Whatever the figures for Carroll County show, only a test tells you about one home.
Testing
- Short-term test kitsPassive detectors exposed for a few days under closed-building conditions, then analyzed by a lab.
- Long-term test kitsDetectors exposed for more than 90 days, for a closer picture of the annual average.
- Continuous monitorsPowered devices that log radon on a repeating cycle, often used for transaction tests.
- Digital detectorsConsumer devices that display a running radon reading without a lab.
- Water radon testsKits for radon dissolved in well water, analyzed by a lab.
Mitigation
- Mitigation fansThe inline fan that keeps a soil depressurization system running, sized by the installer.
- System indicatorsU-tube manometers and fan alarms that show whether a mitigation system is still working.
- Sealing materialsCrack, joint and sump sealing used alongside a mitigation system, not instead of one.
Carroll County / Next steps
What to do next
Learn
Know what radon is
What radon is, how it gets indoors, and why a county zone is not a reading for your home.
Learn about radonTest
Test the building you live in
Short-term or long-term, where the device goes, and closed-house conditions.
How to testFix
Bring a high level down
How a mitigation system works, and the retest that confirms it.
How mitigation worksFind a pro
Hire a certified professional
Measurement and mitigation professionals by state, with their certifications.
Find a professional
Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.