Is Putnam County, IL a radon risk area?

EPA's own radon map rates Putnam County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally, Putnam County ranks higher in radon potential than 71% of rated counties (the 71st percentile).

Putnam County by the numbers

About 5,633 people live in Putnam County, Illinois, spread over 160.097 square miles. That works out to roughly 35 people per square mile. Rank 898 by population within its EPA zone puts Putnam County at the 16th percentile among zone peers. EPA's geology-based Region 5 groups Putnam County with 523 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Putnam County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Being in Zone 1 raises the odds Putnam County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

Next steps for a home in Putnam County

Nothing about Putnam 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

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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.