Radon in Delaware
About 1 in 6 homes tested in Delaware were at or above the EPA action level of 4 pCi/L.
- Below 2 pCi/L: 55%
- 2 to 4 pCi/L: 28%
- 4 pCi/L or more: 17%
The EPA puts 0 of Delaware's 3 counties in Zone 1, its highest radon category, 1 in Zone 2 and 2 in Zone 3.
Every county in Delaware
Sorted by the share of homes tested at or above 4 pCi/L. Select a county for local details and costs.
| County | Homes tested | At or above 4 | Median | EPA zone |
|---|---|---|---|---|
| New Castle County | 17% | 1.8 pCi/L | 2 | |
| Kent County | 17% | 1.6 pCi/L | 3 | |
| Sussex County | 10% | 1.0 pCi/L | 3 |
"–" means fewer than 20 tests or no lab data, too few for a reliable figure.
Sources
- EPA Map of Radon Zones (public domain).
- CDC Environmental Public Health Tracking Network, radon tests from labs, 2008–2017. Pre-mitigation tests only.
Last updated October 2026. How we calculate these numbers.