Is Dane County, WI a radon risk area?

Dane County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Dane County in the 99th percentile nationally for radon potential — higher than 99% of the counties EPA has rated.

How Dane County compares

About 588,347 people live in Dane County, Wisconsin, spread over 1,196.496 square miles. Averaged across its land area, Dane County runs about 492 people per square mile. Rank 30 by population within its EPA zone puts Dane County at the 97th percentile among zone peers. Dane County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Dane 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. Some Dane County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

If Dane County tests above the action level

Nothing about Dane 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 Wisconsin's state radon program

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

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