Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Windham County, Connecticut
EPA puts Windham County in Zone 2, its middle radon zone, and 39.4% of its 160 reported radon tests (2019) 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
39.4%
4.3 pts above CT
- Windham
- 39.4%
- CT
- 35.1%
160 tests, 2019
Median result
2.1pCi/L
Below action level
- Windham
- 2.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2019
Tests reported
160
8th of 8 by tests
- Windham
- 160
- Fairfield
- 2,784
Reported to CDC before any fix, 2019
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 CT
2 of 8
Top quarter
- Windham
- 39.4%
- New London
- 48.5%
By share, of 8 with 30+ tests
Read a result for Windham County
Starts at Windham County's median, 2.1 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.1 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. Windham County's median reported result, 2019.
The data
Windham County, At a glance
Windham County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Windham County is a
USGS geologic potential: Moderate across 81% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Windham County, 2019
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 75.0% |
| 2015 | 78.9% |
| 2016 | 71.3% |
| 2017 | 81.9% |
| 2018 | 67.2% |
| 2019 | 39.4% |
2019: 39.4%. Across these years the share ran from 39.4% to 81.9%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 160 tests reported to CDC for Windham County over 2019, 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: 2019. Measured data period: 2005 to 2019 (every CDC figure on file).
Windham County, Compared
Windham County radon figures, compared
Calculated by Radon411In Windham County, about 4 in 10 reported tests in 2019 (63 of 160) were at or above EPA's action level. Against the national pool of 29.0%, the gap is 10.4 points higher. Across 8 Connecticut counties pooled together, 35.1% of tests reached that level, so Windham County runs 4.3 points above its state.
Of 2 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 29.4% (Tolland County) to 48.5% (New London County). By share, Windham County is 2nd of 8 Connecticut counties with 30 or more tests for the same period.
Year by year, 2014 opened at 75.0% and 2019 closed at 39.4% (down 35.6 points), with 2017 the high at 81.9%. Half the tests came in under 2.1 pCi/L and half over it; the single highest reached 38.0 pCi/L. Below the action level, 79 tests (49.4%) came in under 2 pCi/L, against 47.9% statewide, and 18 tests (11.3%) fell between 2 and 4, against 17.0% statewide.
Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 39.4% share point the same way here. USGS geology rates 81% of the county's land moderate radon potential.
The busiest year on file was 2016, with 171 tests reported; the quietest, 2018, had 58.
Windham CountyConnecticut, pooled
| Year | Tests | Windham County, at or above 4 pCi/L | Connecticut, pooled |
|---|---|---|---|
| 2014 | 76 | 75.0% | 53.1% |
| 2015 | 133 | 78.9% | 63.4% |
| 2016 | 171 | 71.3% | 45.1% |
| 2017 | 105 | 81.9% | 38.3% |
| 2018 | 58 | 67.2% | 31.0% |
| 2019 | 160 | 39.4% | 35.1% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Windham County, Geology
The ground under Windham County
PredictedMost of the ground under Windham County is one class on USGS's geologic map: 81.2% of its land is moderate radon potential, with 18.8% high. The map puts 75.2% of Windham County in the area it calls Merrimack Synclinorium and 17.4% in Avalonian Terrane, with 3 smaller areas beside them. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 12, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Merrimack Synclinorium | Schist, gneiss, gabbro. | Moderate | 11 | 75.2% |
| Avalonian Terrane | Proterozoic rocks/Lake Char Fault/Hope Valley Alaskite | High | 12 | 17.4% |
| Esmond-Dedham Subterrane | Esmond granite, including fine-grained granite, granite, granodiorite, augen granite gneiss, granite gneiss, schist, amphibolite, and quartzite. | Moderate | 11 | 6.0% |
| Avalonian Terrane | Mafic gneiss and granite. | High | 12 | 0.8% |
| Scituate Igneous Suite | Fine grained granite, alkali-feldspar granite, and granite. | High | 15 | 0.6% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Windham County beside the ground around it
Connecticut as a whole has more high-potential ground than Windham County: 44.1% of its land, against 18.8% here. Of the 5 counties that border it, 4 have more high-potential ground, Worcester County, MA the most at 85.4%.
The map rates the ground, not the air in any home.
Local help
Windham County, Local resources
Radon testing and mitigation in Windham County
- Radon ProgramRadon Program, run by Department of Public Health, does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Connecticut.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
A part of the partnership includes providing LHDs free short-term radon in air test kits for distribution to community residents.
- Compare kits
- Professionals in Connecticut71 professionals are listed in Connecticut.
What Connecticut's program says
- Phone
- (860) 509-7300
- DPH.RadonReports@ct.gov
- Licensing of radon professionals
The State of Connecticut does not license or otherwise certify radon professionals, however, the Radon Program maintains lists of nationally certified professionals in accordance with the requirements of CGS § 19a-14b (5)(b).
What it means
Windham County, Questions
Questions about radon in Windham County
Are radon levels high in Windham County?
In 2019, 39.4% of the radon tests reported to CDC for Windham County, Connecticut were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.1 pCi/L. Of 8 Connecticut counties with 30 or more tests for the same period, 1 reported a higher share; pooled, the state comes to 35.1%.
Which counties border Windham County?
Windham County borders 5 counties: Tolland County, CT, Kent County, RI, Providence County, RI, New London County, CT and Worcester County, MA.
Products
Windham County, Products
Testing a home in Windham County
In Windham County, 39.4% of 160 tests reported to CDC in 2019 reached 4 pCi/L, against 35.1% pooled across Connecticut. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Windham 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
Hello Radon C battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Windham County, Bordering counties
Counties bordering Windham County
Calculated by Radon411- Radon levels in New London County, CTEPA zone 1
48.5%at or above 4 pCi/L
Median 3.5 pCi/L · 396 tests · 9.1 points above Windham County
- Radon levels in Tolland County, CTEPA zone 2
29.4%at or above 4 pCi/L
Median 1.8 pCi/L · 221 tests · 10.0 points below Windham County
- Radon levels in Kent County, RIEPA zone 1
No CDC figure for 2019; its page reads it against its own neighbours.
- Radon levels in Providence County, RIEPA zone 2
No CDC figure for 2019; its page reads it against its own neighbours.
- Radon levels in Worcester County, MAEPA zone 1
No CDC figure for 2019; its page reads it against its own neighbours.
Windham County, Cities and towns
Cities and towns in Windham County
Danielson is its largest town, with 4,265 residents.
Danielson is the one incorporated place here; CDC publishes no figure by town, so it reads Windham County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Danielson | 4,265 | +2.5% | Not published |
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).