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

EPA places Fayette County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally that's the 47th percentile for radon potential — Fayette County outranks 47% of every county EPA has rated.

Fayette County by the numbers

Fayette County, Illinois is home to about 21,157 people across 716.451 square miles. Averaged across its land area, Fayette County runs about 30 people per square mile. By population, Fayette County is the 605th largest of every county sharing its EPA zone — the 41st percentile by population within that zone. EPA's geology-based Region 5 groups Fayette County with 523 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Fayette County

Fayette County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). Fayette County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

If Fayette County tests above the action level

For a Fayette 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 Fayette County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Fayette 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 Fayette County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Fayette County carries, the zone explainer covers what it does and doesn't tell you about any one house.