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 Haven County, Connecticut
EPA puts New Haven County in Zone 1, its highest radon zone, and 37.9% of its 1,007 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
37.9%
2.8 pts above CT
- New Haven
- 37.9%
- CT
- 35.1%
1,007 tests, 2019
Median result
2.2pCi/L
Below action level
- New Haven
- 2.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2019
Tests reported
1,007
2nd of 8 by tests
- New Haven
- 1,007
- 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
3 of 8
Middle half
- New Haven
- 37.9%
- New London
- 48.5%
By share, of 8 with 30+ tests
Read a result for New Haven County
Starts at New Haven 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. New Haven County's median reported result, 2019.
The data
New Haven County, At a glance
New Haven County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of New Haven County in
USGS geologic potential: High across 55% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for New Haven County, 2019
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 52.9% |
| 2015 | 63.0% |
| 2016 | 49.7% |
| 2017 | 47.3% |
| 2018 | 31.3% |
| 2019 | 37.9% |
2019: 37.9%. Across these years the share ran from 31.3% to 63.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 1,007 tests reported to CDC for New Haven 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 Haven County, Compared
New Haven County radon figures, compared
Calculated by Radon411In New Haven County, about 4 in 10 reported tests in 2019 (382 of 1,007) were at or above EPA's action level. Against the national pool of 29.0%, the gap is 8.9 points higher. Across 8 Connecticut counties pooled together, 35.1% of tests reached that level, so New Haven County runs 2.8 points above its state.
Of 4 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 31.5% (Hartford County) to 34.5% (Middlesex County). By share, New Haven County is 3rd of 8 Connecticut counties with 30 or more tests for the same period.
Year by year, 2014 opened at 52.9% and 2019 closed at 37.9% (down 15.0 points), with 2015 the high at 63.0%. Half the tests came in under 2.2 pCi/L and half over it; the single highest reached 89.3 pCi/L. Below the action level, 460 tests (45.7%) came in under 2 pCi/L, against 47.9% statewide, and 165 tests (16.4%) fell between 2 and 4, against 17.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 37.9% share point the same way here. USGS geology rates 55% of the county's land high radon potential.
The busiest year on file was 2015, with 1,011 tests reported; the quietest, 2018, had 658.
New Haven CountyConnecticut, pooled
| Year | Tests | New Haven County, at or above 4 pCi/L | Connecticut, pooled |
|---|---|---|---|
| 2014 | 854 | 52.9% | 53.1% |
| 2015 | 1,011 | 63.0% | 63.4% |
| 2016 | 817 | 49.7% | 45.1% |
| 2017 | 672 | 47.3% | 38.3% |
| 2018 | 658 | 31.3% | 31.0% |
| 2019 | 1,007 | 37.9% | 35.1% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
New Haven County, Geology
The ground under New Haven County
PredictedUSGS's geologic map splits New Haven County: 54.8% of its land is high radon potential and 6.5% moderate and 38.2% low. The map puts 38.2% of New Haven County in the area it calls Newark Terrane (Mesozoic Basins) and 38.2% in Connecticut Valley Synclinorium, with 3 smaller areas beside them. USGS gives the first a radon index of 8, in the low band (5 to 8), and the second 12, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Newark Terrane (Mesozoic Basins) | Sedimentary and igneous rocks including dolerite, arkose, basalt. | Low | 8 | 38.2% |
| Connecticut Valley Synclinorium | Schist, gneiss and phyllite. | High | 12 | 38.2% |
| Bronson Hill Anticlinorium | Granite gneiss, schist, amphibolite. | High | 12 | 10.3% |
| Taconic Allochthons | Cambrian schist. | Moderate | 11 | 6.5% |
| Avalonian Terrane | Proterozoic rocks/Lake Char Fault/Hope Valley Alaskite | High | 12 | 6.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
New Haven County beside the ground around it
New Haven County has more high-potential ground than Connecticut as a whole: 54.8% of its land against 44.1%. Of the 4 counties that border it, 2 have more high-potential ground, Fairfield County the most at 79.5%.
The map rates the ground, not the air in any home.
Local help
New Haven County, Local resources
Radon testing and mitigation in New Haven County
Listed radon businesses with an address in New Haven 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: Meriden, Milford, Naugatuck, Ansonia, Derby
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 Haven County, Questions
Questions about radon in New Haven County
Are radon levels high in New Haven County?
In 2019, 37.9% of the radon tests reported to CDC for New Haven County, Connecticut were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.2 pCi/L. Of 8 Connecticut counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 35.1%.
Which counties border New Haven County?
New Haven County borders 4 counties: Middlesex County, Fairfield County, Hartford County and Litchfield County.
Products
New Haven County, Products
Testing a home in New Haven County
In New Haven County, 37.9% of 1,007 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 Haven 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
Monitor
Corentium Home battery digital radon detector
- C-NRPP 2024/25: Approved
- Battery
- Screen
Method: Alpha spectrometry
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
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
New Haven County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like New Haven County
Explore
New Haven County, Bordering counties
Counties bordering New Haven County
Calculated by Radon411- Radon levels in Middlesex CountyEPA zone 1
34.5%at or above 4 pCi/L
Median 2.0 pCi/L · 571 tests · 3.4 points below New Haven County
- Radon levels in Litchfield CountyEPA zone 2
33.8%at or above 4 pCi/L
Median 2.0 pCi/L · 346 tests · 4.1 points below New Haven County
- Radon levels in Fairfield CountyEPA zone 1
33.4%at or above 4 pCi/L
Median 2.1 pCi/L · 2,784 tests · 4.5 points below New Haven County
- Radon levels in Hartford CountyEPA zone 3
31.5%at or above 4 pCi/L
Median 1.4 pCi/L · 606 tests · 6.4 points below New Haven County
New Haven County, Cities and towns
Cities and towns in New Haven County
New Haven is its largest town, with 138,774 residents.
From New Haven to Woodmont, CDC publishes no figure by town: each reads New Haven County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| New Haven | 138,774 | +7.3% | Not published |
| Waterbury | 115,771 | +1.7% | Not published |
| Meriden | 60,810 | +0.3% | Not published |
| West Haven | 55,351 | −0.3% | Not published |
| Milford | 51,215 | +1.6% | Not published |
| Naugatuck | 32,230 | +2.3% | Not published |
| Ansonia | 19,216 | +1.7% | Not published |
| Derby | 12,925 | +5.0% | Not published |
| Woodmont | 2,391 | +53.9% | Not published |
9 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).