What EPA's radon map says about Lyon County

Lyon County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Lyon County ranks higher in radon potential than 77% of rated counties (the 77th percentile).

Where Lyon County sits nationally

About 12,378 people live in Lyon County, Iowa, spread over 587.609 square miles. That works out to roughly 21 people per square mile. Among counties sharing Lyon County's EPA zone, it outranks 33% of them by population. Geologically, Lyon County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Zone vs. an actual test

Lyon County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. Some Lyon County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Next steps for a home in Lyon County

Mitigation cost doesn't depend on Lyon County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Iowa's state radon program

Lyon County's test kit answers today; a Airthings radon monitor keeps answering for Lyon County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.