Carroll County, IA: EPA's radon zone, explained

EPA's own radon map rates Carroll County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally, Carroll County ranks higher in radon potential than 82% of rated counties (the 82nd percentile).

Where Carroll County sits nationally

Carroll County, Iowa is home to about 20,407 people across 569.453 square miles. That works out to roughly 36 people per square mile. By population, Carroll County is the 570th largest of every county sharing its EPA zone — the 47th percentile by population within that zone. EPA's geology-based Region 7 groups Carroll County with 411 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Carroll County

Carroll County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. 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 Carroll County specifically.

Testing and mitigation in Carroll County

For a Carroll 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 Iowa's state radon program

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

Where Carroll County's figures come from

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