What EPA's radon map says about Butler County

Butler 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 78th percentile for radon potential — Butler County outranks 78% of every county EPA has rated.

Butler County by the numbers

About 14,156 people live in Butler County, Iowa, spread over 580.138 square miles. That works out to roughly 24 people per square mile. Among counties sharing Butler County's EPA zone, it outranks 36% of them by population. EPA's geology-based Region 7 groups Butler County with 411 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Butler County

Where the national indoor average runs about 1.3 pCi/L, Butler County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Being in Zone 1 raises the odds Butler 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 Butler County

Mitigation cost doesn't depend on Butler 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 Iowa's state radon program

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

The methodology guide shows exactly which EPA and Census sources feed Butler County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.