De Witt County, IL: EPA's radon zone, explained

De Witt County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, De Witt County ranks higher in radon potential than 79% of rated counties (the 79th percentile).

How De Witt County compares

De Witt County, Illinois is home to about 15,319 people across 397.561 square miles. Averaged across its land area, De Witt County runs about 39 people per square mile. By population, De Witt County is the 652nd largest of every county sharing its EPA zone — the 39th percentile by population within that zone. De Witt County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in De Witt County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line De Witt County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. That doesn't mean every De Witt 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 De Witt County

For a De Witt County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Illinois's state radon program

For De Witt County, an ongoing number beats a one-time test - a Airthings radon monitor tracks De Witt County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where De Witt County's figures come from

De Witt County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.