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
Locations and reports
Radon Levels in Middlesex County, Connecticut
EPA puts Middlesex County in Zone 1, its highest radon zone, and 34.5% of its 571 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
34.5%
0.6 pts below CT
- Middlesex
- 34.5%
- CT
- 35.1%
571 tests, 2019
Median result
2.0pCi/L
Below action level
- Middlesex
- 2.0 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2019
Tests reported
571
4th of 8 by tests
- Middlesex
- 571
- 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
4 of 8
Middle half
- Middlesex
- 34.5%
- New London
- 48.5%
By share, of 8 with 30+ tests
Read a result for Middlesex County
Starts at Middlesex County's median, 2.0 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.0 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. Middlesex County's median reported result, 2019.
The data
Middlesex County, At a glance
Middlesex County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Middlesex County in
USGS geologic potential: High across 57% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Middlesex County, 2019
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 55.6% |
| 2015 | 65.6% |
| 2016 | 59.1% |
| 2017 | 53.3% |
| 2018 | 43.8% |
| 2019 | 34.5% |
2019: 34.5%. Across these years the share ran from 34.5% to 65.6%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 571 tests reported to CDC for Middlesex 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).
Middlesex County, Compared
Middlesex County radon figures, compared
Calculated by Radon411In Middlesex County, about 3 in 10 reported tests in 2019 (197 of 571) were at or above EPA's action level. Against the national pool of 29.0%, the gap is 5.5 points higher. Across 8 Connecticut counties pooled together, 35.1% of tests reached that level, so Middlesex County runs 0.6 points below its state.
Of 3 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 31.5% (Hartford County) to 48.5% (New London County). By share, Middlesex County is 4th of 8 Connecticut counties with 30 or more tests for the same period.
Year by year, 2014 opened at 55.6% and 2019 closed at 34.5% (down 21.1 points), with 2015 the high at 65.6%. Half the tests came in under 2.0 pCi/L and half over it; the single highest reached 84.7 pCi/L. Below the action level, 279 tests (48.9%) came in under 2 pCi/L, against 47.9% statewide, and 95 tests (16.6%) fell between 2 and 4, against 17.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 34.5% share point the same way here. USGS geology rates 57% of the county's land high radon potential.
The busiest year on file was 2019, with 571 tests reported; the quietest, 2017, had 321.
Middlesex CountyConnecticut, pooled
| Year | Tests | Middlesex County, at or above 4 pCi/L | Connecticut, pooled |
|---|---|---|---|
| 2014 | 331 | 55.6% | 53.1% |
| 2015 | 489 | 65.6% | 63.4% |
| 2016 | 374 | 59.1% | 45.1% |
| 2017 | 321 | 53.3% | 38.3% |
| 2018 | 370 | 43.8% | 31.0% |
| 2019 | 571 | 34.5% | 35.1% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Middlesex County, Geology
The ground under Middlesex County
PredictedUSGS's geologic map splits Middlesex County: 57.0% of its land is high radon potential and 24.5% moderate and 17.8% low. The map puts 44.0% of Middlesex County in the area it calls Bronson Hill Anticlinorium and 24.5% in Merrimack Synclinorium, 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 11, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Bronson Hill Anticlinorium | Granite gneiss, schist, amphibolite. | High | 12 | 44.0% |
| Merrimack Synclinorium | Schist, gneiss, gabbro. | Moderate | 11 | 24.5% |
| Newark Terrane (Mesozoic Basins) | Sedimentary and igneous rocks including dolerite, arkose, basalt. | Low | 8 | 17.8% |
| Avalonian Terrane | Proterozoic rocks/Lake Char Fault/Hope Valley Alaskite | High | 12 | 13.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Middlesex County beside the ground around it
Middlesex County has more high-potential ground than Connecticut as a whole: 57.0% of its land against 44.1%. Of the 3 counties that border it, 1 has more high-potential ground, New London County the most at 58.4%.
The map rates the ground, not the air in any home.
Local help
Middlesex County, Local resources
Radon testing and mitigation in Middlesex County
Listed radon businesses with an address in Middlesex 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: Middletown
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
Middlesex County, Questions
Questions about radon in Middlesex County
Are radon levels high in Middlesex County?
In 2019, 34.5% of the radon tests reported to CDC for Middlesex County, Connecticut were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.0 pCi/L. Of 8 Connecticut counties with 30 or more tests for the same period, 3 reported a higher share; pooled, the state comes to 35.1%.
Which counties border Middlesex County?
Middlesex County borders 3 counties: New Haven County, Hartford County and New London County.
Products
Middlesex County, Products
Testing a home in Middlesex County
In Middlesex County, 34.5% of 571 tests reported to CDC in 2019 reached 4 pCi/L, against 35.1% pooled across Connecticut. In Zone 1 the year-round level in Middlesex 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 2 battery digital radon monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Screen, app
Method: Alpha spectrometry
Readings: Every 60 minutes
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Middlesex County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Middlesex County
Explore
Middlesex County, Bordering counties
Counties bordering Middlesex County
Calculated by Radon411- Radon levels in New London CountyEPA zone 1
48.5%at or above 4 pCi/L
Median 3.5 pCi/L · 396 tests · 14.0 points above Middlesex County
- Radon levels in New Haven CountyEPA zone 1
37.9%at or above 4 pCi/L
Median 2.2 pCi/L · 1,007 tests · 3.4 points above Middlesex County
- Radon levels in Hartford CountyEPA zone 3
31.5%at or above 4 pCi/L
Median 1.4 pCi/L · 606 tests · 3.0 points below Middlesex County
Middlesex County, Cities and towns
Cities and towns in Middlesex County
Middletown is its largest town, with 48,439 residents.
From Middletown to Fenwick, CDC publishes no figure by town: each reads Middlesex County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Middletown | 48,439 | +3.2% | Not published |
| Fenwick | 44 | +2.3% | Not published |
2 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).