Johnson County, KY: EPA's radon zone, explained

EPA's own radon map rates Johnson County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. That puts Johnson County in the 47th percentile nationally for radon potential — higher than 47% of the counties EPA has rated.

Johnson County by the numbers

Johnson County, Kentucky is home to about 22,098 people across 261.966 square miles. Population density there runs about 84 people per square mile. By population, Johnson County is the 593rd largest of every county sharing its EPA zone — the 43rd percentile by population within that zone. Geologically, Johnson County is grouped into EPA Region 4 alongside 735 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Johnson County's Zone 2 prediction. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Johnson County — testing is the only way to know an individual home's actual level.

Next steps for a home in Johnson County

For a Johnson 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 Kentucky's state radon program

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

The methodology guide shows exactly which EPA and Census sources feed Johnson County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.