Is Madison County, IN a radon risk area?

EPA's own radon map rates Madison County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Madison County sits at the 95th percentile nationally for radon potential — above 95 of every 100 rated counties.

Madison County by the numbers

About 134,222 people live in Madison County, Indiana, spread over 451.921 square miles. Averaged across its land area, Madison County runs about 297 people per square mile. Rank 149 by population within its EPA zone puts Madison County at the 86th percentile among zone peers. Madison 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

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Madison County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Madison 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.

Testing and mitigation in Madison County

Nothing about Madison 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 Indiana's state radon program

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

Madison County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Madison County carries, the zone explainer covers what it does and doesn't tell you about any one house.