What EPA's radon map says about Carroll County

Carroll 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 82nd percentile for radon potential — Carroll County outranks 82% of every county EPA has rated.

Where Carroll County sits nationally

About 20,747 people live in Carroll County, Indiana, spread over 372.225 square miles. Averaged across its land area, Carroll County runs about 56 people per square mile. Among counties sharing Carroll County's EPA zone, it outranks 47% of them by population. Geologically, Carroll 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

Carroll 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. Being in Zone 1 raises the odds Carroll 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.

If Carroll County tests above the action level

Mitigation cost doesn't depend on Carroll County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Indiana's state radon program

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

More on how this number was built

Carroll County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.