What EPA's radon map says about Marion County

EPA's own radon map rates Marion County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Rank it against the rest of the country and Marion County lands in the 77th percentile for radon potential.

Where Marion County sits nationally

About 11,670 people live in Marion County, Kansas, spread over 944.299 square miles. Population density there runs about 12 people per square mile. Among counties sharing Marion County's EPA zone, it outranks 32% of them by population. Geologically, Marion County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Zone vs. an actual test

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Marion County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. That doesn't mean every Marion County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Testing and mitigation in Marion County

Mitigation cost doesn't depend on Marion 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 Kansas's state radon program

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