What EPA's radon map says about Fond du Lac County
EPA places Fond du Lac 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. Fond du Lac County sits at the 94th percentile nationally for radon potential — above 94 of every 100 rated counties.
Fond du Lac County by the numbers
About 104,269 people live in Fond du Lac County, Wisconsin, spread over 719.566 square miles. That works out to roughly 145 people per square mile. Among counties sharing Fond du Lac County's EPA zone, it outranks 83% of them by population. Fond du Lac County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.
What this actually means for a house in Fond du Lac County
Fond du Lac County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. 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 Fond du Lac County specifically.
If Fond du Lac County tests above the action level
Mitigation cost doesn't depend on Fond du Lac 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
Fond du Lac County's test kit answers today; a Airthings radon monitor keeps answering for Fond du Lac 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. Whatever zone Fond du Lac County carries, the zone explainer covers what it does and doesn't tell you about any one house.