Is Thomas County, KS a radon risk area?

EPA places Thomas County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and Thomas County lands in the 74th percentile for radon potential.

Where Thomas County sits nationally

About 7,802 people live in Thomas County, Kansas, spread over 1,074.687 square miles. Population density there runs about 7 people per square mile. Rank 822 by population within its EPA zone puts Thomas County at the 23rd percentile among zone peers. Geologically, Thomas County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

What this actually means for a house in Thomas County

Thomas County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. That doesn't mean every Thomas 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.

If Thomas County tests above the action level

Nothing about Thomas 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 Kansas's state radon program

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

Thomas County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.