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

EPA places Madison County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Madison County in the 59th percentile nationally for radon potential — higher than 59% of the counties EPA has rated.

How Madison County compares

Madison County, Kentucky is home to about 99,582 people across 437.94 square miles. Averaged across its land area, Madison County runs about 227 people per square mile. By population, Madison County is the 203rd largest of every county sharing its EPA zone — the 80th percentile by population within that zone. Madison County falls in EPA Radon Region 4, one of 736 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Madison County's Zone 2 prediction lands in the gap between the two. A county-wide moderate average, like Madison County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Next steps for a home in Madison County

For a Madison 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 Madison County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Madison 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 Madison 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. Whatever zone Madison County carries, the zone explainer covers what it does and doesn't tell you about any one house.