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 Fairfield County, Connecticut
EPA puts Fairfield County in Zone 1, its highest radon zone, and 33.4% of its 2,784 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
33.4%
1.7 pts below CT
- Fairfield
- 33.4%
- CT
- 35.1%
2,784 tests, 2019
Median result
2.1pCi/L
Below action level
- Fairfield
- 2.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2019
Tests reported
2,784
Most tested in CT
- 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
6 of 8
Middle half
- Fairfield
- 33.4%
- New London
- 48.5%
By share, of 8 with 30+ tests
Read a result for Fairfield County
Starts at Fairfield 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. Fairfield County's median reported result, 2019.
The data
Fairfield County, At a glance
Fairfield County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Fairfield County in
USGS geologic potential: High across 80% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Fairfield County, 2019
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 50.1% |
| 2015 | 58.5% |
| 2016 | 36.8% |
| 2017 | 27.5% |
| 2018 | 26.9% |
| 2019 | 33.4% |
2019: 33.4%. Across these years the share ran from 26.9% to 58.5%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 2,784 tests reported to CDC for Fairfield 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).
Fairfield County, Compared
Fairfield County radon figures, compared
Calculated by Radon411In Fairfield County, about 3 in 10 reported tests in 2019 (929 of 2,784) were at or above EPA's action level. Against the national pool of 29.0%, the gap is 4.4 points higher. Across 8 Connecticut counties pooled together, 35.1% of tests reached that level, so Fairfield County runs 1.7 points below its state.
Of 5 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 13.0% (Westchester County, NY) to 38.1% (Putnam County, NY). By share, Fairfield County is 6th of 8 Connecticut counties with 30 or more tests for the same period.
Year by year, 2014 opened at 50.1% and 2019 closed at 33.4% (down 16.7 points), with 2015 the high at 58.5%. Half the tests came in under 2.1 pCi/L and half over it; the single highest reached 79.0 pCi/L. Below the action level, 1,322 tests (47.5%) came in under 2 pCi/L, against 47.9% statewide, and 533 tests (19.1%) fell between 2 and 4, against 17.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 33.4% share point the same way here. USGS geology rates 80% of the county's land high radon potential.
The busiest year on file was 2015, with 3,082 tests reported; the quietest, 2018, had 2,225.
Fairfield CountyConnecticut, pooled
| Year | Tests | Fairfield County, at or above 4 pCi/L | Connecticut, pooled |
|---|---|---|---|
| 2014 | 2,403 | 50.1% | 53.1% |
| 2015 | 3,082 | 58.5% | 63.4% |
| 2016 | 2,540 | 36.8% | 45.1% |
| 2017 | 2,519 | 27.5% | 38.3% |
| 2018 | 2,225 | 26.9% | 31.0% |
| 2019 | 2,784 | 33.4% | 35.1% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Fairfield County, Geology
The ground under Fairfield County
PredictedMost of the ground under Fairfield County is one class on USGS's geologic map: 79.5% of its land is high radon potential, with 19.2% moderate. The map puts 79.5% of Fairfield County in the area it calls Connecticut Valley Synclinorium and 8.7% in Carbonate shelf, with 2 smaller areas beside them. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Connecticut Valley Synclinorium | Schist, gneiss and phyllite. | High | 12 | 79.5% |
| Carbonate shelf | Marble and schist. | Moderate | 9 | 8.7% |
| Proterozoic massifs | Gneiss, granitic gneiss, amphibolite, mica schist. | Moderate | 10 | 8.5% |
| Taconic Allochthons | Cambrian schist. | Moderate | 11 | 2.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Fairfield County beside the ground around it
Fairfield County has more high-potential ground than Connecticut as a whole: 79.5% of its land against 44.1%. Of the 5 counties that border it, 2 have more high-potential ground, Dutchess County, NY the most at 99.6%.
The map rates the ground, not the air in any home.
Local help
Fairfield County, Local resources
Radon testing and mitigation in Fairfield County
Listed radon businesses with an address in Fairfield 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: Bridgeport, Stamford, Norwalk, Danbury, Shelton, Newtown
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
Fairfield County, Questions
Questions about radon in Fairfield County
Are radon levels high in Fairfield County?
In 2019, 33.4% of the radon tests reported to CDC for Fairfield 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, 5 reported a higher share; pooled, the state comes to 35.1%.
Which counties border Fairfield County?
Fairfield County borders 5 counties: New Haven County, CT, Putnam County, NY, Westchester County, NY, Litchfield County, CT and Dutchess County, NY.
Products
Fairfield County, Products
Testing a home in Fairfield County
In Fairfield County, 33.4% of 2,784 tests reported to CDC in 2019 reached 4 pCi/L, against 35.1% pooled across Connecticut. In Zone 1 the year-round level in Fairfield 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
Fairfield County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Fairfield County
Explore
Fairfield County, Bordering counties
Counties bordering Fairfield County
Calculated by Radon411- Radon levels in Putnam County, NYEPA zone 1
38.1%at or above 4 pCi/L
Median 2.5 pCi/L · 42 tests · 4.7 points above Fairfield County
- Radon levels in New Haven County, CTEPA zone 1
37.9%at or above 4 pCi/L
Median 2.2 pCi/L · 1,007 tests · 4.5 points above Fairfield County
- Radon levels in Dutchess County, NYEPA zone 1
36.8%at or above 4 pCi/L
Median 2.3 pCi/L · 38 tests · 3.4 points above Fairfield County
- Radon levels in Litchfield County, CTEPA zone 2
33.8%at or above 4 pCi/L
Median 2.0 pCi/L · 346 tests · 0.4 points above Fairfield County
- Radon levels in Westchester County, NYEPA zone 3
13.0%at or above 4 pCi/L
Median 2.0 pCi/L · 46 tests · 20.4 points below Fairfield County
Fairfield County, Cities and towns
Cities and towns in Fairfield County
Bridgeport is its largest town, with 152,273 residents.
From Bridgeport to Newtown, CDC publishes no figure by town: each reads Fairfield County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Bridgeport | 152,273 | +3.1% | Not published |
| Stamford | 139,535 | +3.0% | Not published |
| Norwalk | 94,508 | +3.9% | Not published |
| Danbury | 89,033 | +3.4% | Not published |
| Shelton | 42,880 | +5.3% | Not published |
| Newtown | 1,980 | +4.0% | Not published |
Places in Fairfield County with a city page: 1 of 2
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).