Is Franklin County, IL a radon risk area?

EPA places Franklin 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. Franklin County sits at the 52nd percentile nationally for radon potential — above 52 of every 100 rated counties.

How Franklin County compares

About 37,033 people live in Franklin County, Illinois, spread over 408.935 square miles. Averaged across its land area, Franklin County runs about 91 people per square mile. Rank 424 by population within its EPA zone puts Franklin County at the 59th percentile among zone peers. Geologically, Franklin County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

What this actually means for a house in Franklin County

Franklin County's Zone 2 prediction clears the 1.3 pCi/L national indoor average without reaching EPA's own 4 pCi/L point for recommending a fix. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Franklin County — testing is the only way to know an individual home's actual level.

Testing and mitigation in Franklin County

Nothing about Franklin 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

Franklin County's test kit answers today; a Airthings radon monitor keeps answering for Franklin 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

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