What EPA's radon map says about Madison County

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 43rd percentile nationally for radon potential — higher than 43% of the counties EPA has rated.

How Madison County compares

About 14,252 people live in Madison County, Virginia, spread over 320.638 square miles. That works out to roughly 44 people per square mile. Among counties sharing Madison County's EPA zone, it outranks 29% of them by population. Madison County falls in EPA Radon Region 3, one of 245 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

EPA's Zone 2 rating for Madison County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Madison County — testing is the only way to know an individual home's actual level.

If Madison County tests above the action level

Mitigation cost doesn't depend on Madison 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 Virginia's state radon program

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

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Madison County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.