Peoria County, IL: EPA's radon zone, explained
EPA places Peoria 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. Peoria County sits at the 97th percentile nationally for radon potential — above 97 of every 100 rated counties.
How Peoria County compares
Peoria County, Illinois is home to about 179,630 people across 618.695 square miles. Population density there runs about 290 people per square mile. By population, Peoria County is the 106th largest of every county sharing its EPA zone — the 90th percentile by population within that zone. EPA's geology-based Region 5 groups Peoria County with 523 other counties nationally sharing its underlying rock and soil profile.
Zone vs. an actual test
Where the national indoor average runs about 1.3 pCi/L, Peoria County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Some Peoria 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.
Next steps for a home in Peoria County
For a Peoria 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 Peoria County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Peoria 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 Peoria County's figures come from
Peoria County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Peoria County carries, the zone explainer covers what it does and doesn't tell you about any one house.