Is Iroquois County, IL a radon risk area?

EPA places Iroquois 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. Rank it against the rest of the country and Iroquois County lands in the 84th percentile for radon potential.

Iroquois County by the numbers

About 26,067 people live in Iroquois County, Illinois, spread over 1,117.408 square miles. That works out to roughly 23 people per square mile. Rank 504 by population within its EPA zone puts Iroquois County at the 53rd percentile among zone peers. Geologically, Iroquois County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Iroquois 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. Some Iroquois 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.

If Iroquois County tests above the action level

Nothing about Iroquois 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

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

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Iroquois County's numbers. Whatever zone Iroquois County carries, the zone explainer covers what it does and doesn't tell you about any one house.