What EPA's radon map says about Hillsdale County

Hillsdale 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 Hillsdale County in the 89th percentile nationally for radon potential — higher than 89% of the counties EPA has rated.

Where Hillsdale County sits nationally

About 45,590 people live in Hillsdale County, Michigan, spread over 598.167 square miles. That works out to roughly 76 people per square mile. Among counties sharing Hillsdale County's EPA zone, it outranks 68% of them by population. EPA's geology-based Region 5 groups Hillsdale County with 523 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Hillsdale 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 Hillsdale County specifically.

If Hillsdale County tests above the action level

Mitigation cost doesn't depend on Hillsdale 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 Michigan's state radon program

Hillsdale County's test kit answers today; a Airthings radon monitor keeps answering for Hillsdale County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Hillsdale County's numbers. Whatever zone Hillsdale County carries, the zone explainer covers what it does and doesn't tell you about any one house.