What EPA's radon map says about Johnson County

Johnson County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Johnson County sits at the 71st percentile nationally for radon potential — above 71 of every 100 rated counties.

How Johnson County compares

About 5,219 people live in Johnson County, Nebraska, spread over 376.086 square miles. That works out to roughly 14 people per square mile. Among counties sharing Johnson County's EPA zone, it outranks 14% of them by population. Geologically, Johnson County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Zone vs. an actual test

Johnson 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 Johnson 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 Johnson County tests above the action level

Mitigation cost doesn't depend on Johnson 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 Nebraska's state radon program

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