What EPA's radon map says about Door County

EPA's own radon map rates Door County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Door County sits at the 85th percentile nationally for radon potential — above 85 of every 100 rated counties.

Where Door County sits nationally

About 30,512 people live in Door County, Wisconsin, spread over 481.936 square miles. Averaged across its land area, Door County runs about 63 people per square mile. Among counties sharing Door County's EPA zone, it outranks 57% of them by population. EPA's geology-based Region 5 groups Door County with 523 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Door County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. 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 Door County specifically.

If Door County tests above the action level

Mitigation cost doesn't depend on Door 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 Wisconsin's state radon program

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

Door County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.