Is Vermilion County, IL a radon risk area?

Vermilion County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally that's the 92nd percentile for radon potential — Vermilion County outranks 92% of every county EPA has rated.

Where Vermilion County sits nationally

About 71,106 people live in Vermilion County, Illinois, spread over 898.32 square miles. That works out to roughly 79 people per square mile. Rank 245 by population within its EPA zone puts Vermilion County at the 77th percentile among zone peers. Vermilion 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

Vermilion County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Vermilion County specifically.

Testing and mitigation in Vermilion County

Nothing about Vermilion County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Illinois's state radon program

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

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Vermilion County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.