Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in New London County, Connecticut
EPA puts New London County in Zone 1, its highest radon zone, and high results are common there: 48.5% of the 396 radon tests reported to CDC (2019) 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
48.5%
13.4 pts above CT
- New London
- 48.5%
- CT
- 35.1%
396 tests, 2019
Median result
3.5pCi/L
Below action level
- New London
- 3.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2019
Tests reported
396
5th of 8 by tests
- New London
- 396
- Fairfield
- 2,784
Reported to CDC before any fix, 2019
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in CT
1 of 8
Top quarter
- New London
- 48.5%
- New London
- 48.5%
By share, of 8 with 30+ tests
Read a result for New London County
Starts at New London County's median, 3.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.5 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. New London County's median reported result, 2019.
The data
New London County, At a glance
New London County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of New London County in
USGS geologic potential: High across 58% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for New London County, 2019
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 78.3% |
| 2015 | 87.6% |
| 2016 | 54.6% |
| 2017 | 58.3% |
| 2018 | 60.5% |
| 2019 | 48.5% |
2019: 48.5%. Across these years the share ran from 48.5% to 87.6%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 396 tests reported to CDC for New London 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).
New London County, Compared
New London County radon figures, compared
Calculated by Radon411In New London County, about 5 in 10 reported tests in 2019 (192 of 396) were at or above EPA's action level. Against the national pool of 29.0%, the gap is 19.5 points higher. Across 8 Connecticut counties pooled together, 35.1% of tests reached that level, so New London County runs 13.4 points above its state.
Of 4 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 29.4% (Tolland County) to 39.4% (Windham County). By share, New London County is 1st of 8 Connecticut counties with 30 or more tests for the same period.
Year by year, 2014 opened at 78.3% and 2019 closed at 48.5% (down 29.8 points), with 2015 the high at 87.6%. Half the tests came in under 3.5 pCi/L and half over it; the single highest reached 207.0 pCi/L. Below the action level, 150 tests (37.9%) came in under 2 pCi/L, against 47.9% statewide, and 54 tests (13.6%) fell between 2 and 4, against 17.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 48.5% share point the same way here. USGS geology rates 58% of the county's land high radon potential.
The busiest year on file was 2019, with 396 tests reported; the quietest, 2014, had 184.
New London CountyConnecticut, pooled
48.5% % of tests35.1% % of tests
| Year | Tests | New London County, at or above 4 pCi/L | Connecticut, pooled |
|---|---|---|---|
| 2014 | 184 | 78.3% | 53.1% |
| 2015 | 330 | 87.6% | 63.4% |
| 2016 | 368 | 54.6% | 45.1% |
| 2017 | 343 | 58.3% | 38.3% |
| 2018 | 200 | 60.5% | 31.0% |
| 2019 | 396 | 48.5% | 35.1% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
New London County, Geology
The ground under New London County
PredictedUSGS's geologic map splits New London County: 58.4% of its land is high radon potential and 39.9% moderate. The map puts 57.9% of New London County in the area it calls Avalonian Terrane and 39.6% in Merrimack Synclinorium. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 11, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Avalonian Terrane | Proterozoic rocks/Lake Char Fault/Hope Valley Alaskite | High | 12 | 57.9% |
| Merrimack Synclinorium | Schist, gneiss, gabbro. | Moderate | 11 | 39.6% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
New London County beside the ground around it
New London County has more high-potential ground than Connecticut as a whole: 58.4% of its land against 44.1%. Of the 6 counties that border it, 2 have more high-potential ground, Kent County, RI the most at 75.5%.
The map rates the ground, not the air in any home.
Local help
New London County, Local resources
Radon testing and mitigation in New London County
Listed radon businesses with an address in New London 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.
Listed radon professionals by town: Groton
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
New London County, Questions
Questions about radon in New London County
Are radon levels high in New London County?
In 2019, 48.5% of the radon tests reported to CDC for New London County, Connecticut were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.5 pCi/L. Of 8 Connecticut counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 35.1%.
Which counties border New London County?
New London County borders 6 counties: Windham County, CT, Washington County, RI, Middlesex County, CT, Kent County, RI, Tolland County, CT and Hartford County, CT.
Products
New London County, Products
Testing a home in New London County
In New London County, 48.5% of 396 tests reported to CDC in 2019 reached 4 pCi/L, against 35.1% pooled across Connecticut. In Zone 1 the year-round level in New London County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
MonitorAEGTEST
HOUND-3699 radon monitor with a 2.1-inch touchscreen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
First reading: Within 1 hour
Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
New London County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like New London County
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New London County, Bordering counties
Counties bordering New London County
Calculated by Radon411- Radon levels in Windham County, CTEPA zone 2
39.4%at or above 4 pCi/L
Median 2.1 pCi/L · 160 tests · 9.1 points below New London County
- Radon levels in Middlesex County, CTEPA zone 1
34.5%at or above 4 pCi/L
Median 2.0 pCi/L · 571 tests · 14.0 points below New London County
- Radon levels in Hartford County, CTEPA zone 3
31.5%at or above 4 pCi/L
Median 1.4 pCi/L · 606 tests · 17.0 points below New London County
- Radon levels in Tolland County, CTEPA zone 2
29.4%at or above 4 pCi/L
Median 1.8 pCi/L · 221 tests · 19.1 points below New London County
- Radon levels in Washington County, RIEPA zone 1
No CDC figure for 2019; its page reads it against its own neighbours.
- Radon levels in Kent County, RIEPA zone 1
No CDC figure for 2019; its page reads it against its own neighbours.
New London County, Cities and towns
Cities and towns in New London County
Norwich is its largest town, with 40,001 residents.
From Norwich to Groton Long Point, CDC publishes no figure by town: each reads New London County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Norwich | 40,001 | −0.1% | Not published |
| New London | 28,003 | +4.5% | Not published |
| Groton | 10,160 | +8.5% | Not published |
| Jewett City | 3,456 | +1.9% | Not published |
| Stonington | 1,017 | +2.5% | Not published |
| Groton Long Point | 522 | +0.6% | Not published |
6 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).