What EPA's radon map says about Sussex County

Sussex County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. That puts Sussex County in the 30th percentile nationally for radon potential — higher than 30% of the counties EPA has rated.

How Sussex County compares

About 271,134 people live in Sussex County, Delaware, spread over 936.146 square miles. That works out to roughly 290 people per square mile. Among counties sharing Sussex County's EPA zone, it outranks 91% of them by population. Geologically, Sussex County is grouped into EPA Region 3 alongside 244 other counties that share its rock and soil setting.

Zone vs. an actual test

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Sussex County's Zone 3 prediction is the low end of the scale. A Zone 3 rating means Sussex County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

Next steps for a home in Sussex County

Mitigation cost doesn't depend on Sussex County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Delaware's state radon program

Sussex County's test kit answers today; a Airthings radon monitor keeps answering for Sussex County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Sussex County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.