Mackinac County, MI: EPA's radon zone, explained

EPA places Mackinac County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally, Mackinac County ranks higher in radon potential than 8% of rated counties (the 8th percentile).

Mackinac County by the numbers

Mackinac County, Michigan is home to about 11,144 people across 1,021.879 square miles. That works out to roughly 11 people per square mile. By population, Mackinac County is the 788th largest of every county sharing its EPA zone — the 24th percentile by population within that zone. Geologically, Mackinac County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Mackinac County's predicted average sits below the national indoor average of about 1.3 pCi/L, well under EPA's 4 pCi/L action level. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like Mackinac County testing above the action level often enough that skipping a test isn't the safe assumption.

Next steps for a home in Mackinac County

For a Mackinac County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Michigan's state radon program

For Mackinac County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Mackinac County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

Where Mackinac County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Mackinac County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.