Piatt County, IL: EPA's radon zone, explained

EPA places Piatt 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. Piatt County sits at the 80th percentile nationally for radon potential — above 80 of every 100 rated counties.

How Piatt County compares

Piatt County, Illinois is home to about 16,628 people across 439.188 square miles. Averaged across its land area, Piatt County runs about 38 people per square mile. By population, Piatt County is the 625th largest of every county sharing its EPA zone — the 41st percentile by population within that zone. Piatt 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

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Piatt County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Some Piatt County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Piatt County

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

Where Piatt County's figures come from

Piatt 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.