What EPA's radon map says about DeKalb County

EPA places DeKalb County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and DeKalb County lands in the 94th percentile for radon potential.

Where DeKalb County sits nationally

About 101,335 people live in DeKalb County, Illinois, spread over 631.337 square miles. Averaged across its land area, DeKalb County runs about 161 people per square mile. Among counties sharing DeKalb County's EPA zone, it outranks 82% of them by population. DeKalb County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Where the national indoor average runs about 1.3 pCi/L, DeKalb County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. That doesn't mean every DeKalb County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Testing and mitigation in DeKalb County

Mitigation cost doesn't depend on DeKalb 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 Illinois's state radon program

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

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.