Radon Risk in Delaware

Delaware's statewide average radon level is 2.2 pCi/L, which falls below the EPA's action level of 4 pCi/L. That's a reasonable baseline, but statewide averages can mask significant county-to-county variation. Some parts of Delaware run considerably higher than others.

Looking at the zone breakdown: none of Delaware's counties are in the high-risk Zone 1 category, 1 are Zone 2 (moderate), and 2 are Zone 3 (low). Use the county list below to find your area and see the most specific data available.

Within Delaware, the spread is notable. New Castle County has the highest measured average in the state at 2.5 pCi/L. Sussex County sits at the other end with 1.8 pCi/L. Remember: these are averages. Individual homes can test significantly higher or lower than their county average depending on construction, foundation type, and ventilation.

Tipper's recommendation for Delaware residents: if you haven't tested your home, start there. A short-term test kit costs around $15 and gives you a result in 48 hours. If your home tests at or above 4 pCi/L, a professional mitigation system (typically $800–$2,000 depending on your foundation and home size) will reliably bring levels down.