Is Rock County, MN a radon risk area?

EPA places Rock 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. Rock County sits at the 75th percentile nationally for radon potential — above 75 of every 100 rated counties.

Rock County by the numbers

About 9,525 people live in Rock County, Minnesota, spread over 482.459 square miles. Averaged across its land area, Rock County runs about 20 people per square mile. Rank 778 by population within its EPA zone puts Rock County at the 27th percentile among zone peers. Geologically, Rock County is grouped into EPA Region 5 alongside 523 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 Rock County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Rock County specifically.

If Rock County tests above the action level

Nothing about Rock 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 Minnesota's state radon program

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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.