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

EPA's own radon map rates Story County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. That puts Story County in the 94th percentile nationally for radon potential — higher than 94% of the counties EPA has rated.

Story County by the numbers

Story County, Iowa is home to about 102,498 people across 572.545 square miles. Averaged across its land area, Story County runs about 179 people per square mile. By population, Story County is the 190th largest of every county sharing its EPA zone — the 82nd percentile by population within that zone. Story 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 Story County

Story 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 Story 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.

If Story County tests above the action level

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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.