Radon Risk in Illinois

Illinois has a statewide average radon level of 5.01 pCi/L, above the EPA's action level of 4 pCi/L. That puts Illinois among the higher-risk states in the country for indoor radon. If you live here, testing your home is genuinely important.

Looking at the zone breakdown: 56 of Illinois's 102 counties are EPA Zone 1 (high risk), 43 are Zone 2 (moderate), and 3 are Zone 3 (low). That means 55% of the state falls into the highest risk category, counties where the EPA predicts average indoor levels above 4 pCi/L. Use the county list below to find your area and see the most specific data available.

Within Illinois, the spread is notable. Stark County has the highest measured average in the state at 11.9 pCi/L. Pope County sits at the other end with 1.7 pCi/L. 68 counties have a measured average above 4 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 Illinois 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.