Is Delaware County, IN a radon risk area?

Delaware County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Delaware County ranks higher in radon potential than 94% of rated counties (the 94th percentile).

How Delaware County compares

About 112,951 people live in Delaware County, Indiana, spread over 392.109 square miles. Population density there runs about 288 people per square mile. Rank 177 by population within its EPA zone puts Delaware County at the 83rd percentile among zone peers. EPA's geology-based Region 5 groups Delaware County with 523 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Delaware County

Delaware 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 Delaware 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 Delaware County

Nothing about Delaware 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

Delaware County's test kit answers today; a Airthings radon monitor keeps answering for Delaware 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 Delaware County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.