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

Shelby County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally that's the 77th percentile for radon potential — Shelby County outranks 77% of every county EPA has rated.

Where Shelby County sits nationally

Shelby County, Iowa is home to about 11,821 people across 590.776 square miles. Averaged across its land area, Shelby County runs about 20 people per square mile. By population, Shelby County is the 724th largest of every county sharing its EPA zone — the 32nd percentile by population within that zone. Shelby County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Shelby 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. That doesn't mean every Shelby County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Testing and mitigation in Shelby County

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

Shelby County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.