Is Jefferson County, KS a radon risk area?

EPA's own radon map rates Jefferson County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Rank it against the rest of the country and Jefferson County lands in the 45th percentile for radon potential.

Where Jefferson County sits nationally

About 18,332 people live in Jefferson County, Kansas, spread over 532.626 square miles. Averaged across its land area, Jefferson County runs about 34 people per square mile. Rank 656 by population within its EPA zone puts Jefferson County at the 36th percentile among zone peers. Jefferson County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Jefferson County's Zone 2 prediction lands in the gap between the two. Jefferson County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

If Jefferson County tests above the action level

Nothing about Jefferson 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

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

Jefferson County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Jefferson County carries, the zone explainer covers what it does and doesn't tell you about any one house.