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

EPA places Madison County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Madison County sits at the 26th percentile nationally for radon potential — above 26 of every 100 rated counties.

How Madison County compares

Madison County, Mississippi is home to about 114,247 people across 714.212 square miles. That works out to roughly 160 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

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Madison County's Zone 3 prediction is the low end of the scale. Don't read Zone 3 as a pass for Madison County — EPA's guidance to test every home makes no exception for counties predicted low.

If Madison County tests above the action level

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 Mississippi'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. RADONZONE-10OFF at checkout knocks 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.