Radon levels in Connecticut: Low
The model predicts a population-weighted basement average of 1.5 pCi/L across Connecticut's 8 counties - about 16% below the US average of 1.8 pCi/L. Above-ground floors average 1.0 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
4 / 8
EPA Zone 1 counties (50%)
3 / 1
Zone 2 / Zone 3 counties
0
counties predicted ≥ 4 pCi/L
0%
of ZIP codes predicted ≥ 4 pCi/L
Connecticut counties by predicted radon
Sorted highest to lowest predicted basement average. 8 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Windham County | 2.0 pCi/L | 1.3 | Low | EPA Zone 2 | 23 |
| New London County | 1.8 pCi/L | 1.3 | Low | EPA Zone 1 | 27 |
| Tolland County | 1.8 pCi/L | 1.2 | Low | EPA Zone 2 | 15 |
| Litchfield County | 1.8 pCi/L | 1.2 | Low | EPA Zone 2 | 37 |
| Middlesex County | 1.6 pCi/L | 1.1 | Low | EPA Zone 1 | 20 |
| Fairfield County | 1.6 pCi/L | 1.2 | Low | EPA Zone 1 | 46 |
| New Haven County | 1.5 pCi/L | 1.0 | Low | EPA Zone 1 | 40 |
| Hartford County | 1.3 pCi/L | 0.7 | Low | EPA Zone 3 | 54 |
Connecticut radon questions
- Is radon high in Connecticut?
- Connecticut's population-weighted predicted basement average is 1.5 pCi/L, about 16% below the US average of 1.8. 0 of its 8 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 0 are in the 2-4 "consider fixing" range and 8 are below 2. 0% of Connecticut ZIP codes are predicted at 4 or higher.
- Which Connecticut county has the highest radon?
- Windham County has the highest predicted basement average in Connecticut at 2.0 pCi/L (EPA Zone 2). The lowest is Hartford County at 1.3 pCi/L. These are modeled area averages; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Connecticut?
- 4 of Connecticut's 8 counties (50%) are EPA Zone 1 (highest potential), 3 are Zone 2 and 1 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in Connecticut?
- Yes. Even though Connecticut's predicted average is below 2 pCi/L, the EPA recommends every home be tested - radon varies house to house, and 26% of Connecticut ZIP codes are still predicted at 2 pCi/L or higher.
Connecticut radon program
Many states offer free or discounted test kits and keep lists of certified mitigators. Find the Connecticut radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.