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

Linn County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Linn County ranks higher in radon potential than 97% of rated counties (the 97th percentile).

Where Linn County sits nationally

Linn County, Iowa is home to about 231,762 people across 717.013 square miles. That works out to roughly 323 people per square mile. By population, Linn County is the 90th largest of every county sharing its EPA zone — the 92nd percentile by population within that zone. Linn County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Linn County

Linn 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 Linn County specifically.

Next steps for a home in Linn County

For a Linn 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 Linn County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Linn 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 Linn County's figures come from

Linn County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Linn County carries, the zone explainer covers what it does and doesn't tell you about any one house.