Grundy County, MO: EPA's radon zone, explained

Grundy County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Grundy County sits at the 40th percentile nationally for radon potential — above 40 of every 100 rated counties.

Where Grundy County sits nationally

Grundy County, Missouri is home to about 9,766 people across 435.293 square miles. Population density there runs about 22 people per square mile. By population, Grundy County is the 824th largest of every county sharing its EPA zone — the 20th percentile by population within that zone. Geologically, Grundy County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Grundy County's Zone 2 prediction lands in the gap between the two. A county-wide moderate average, like Grundy County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Next steps for a home in Grundy County

For a Grundy 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 Missouri's state radon program

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

Where Grundy County's figures come from

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