What EPA's radon map says about Sullivan County

EPA places Sullivan 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. Nationally, Sullivan County ranks higher in radon potential than 36% of rated counties (the 36th percentile).

How Sullivan County compares

About 5,750 people live in Sullivan County, Missouri, spread over 647.982 square miles. Population density there runs about 9 people per square mile. Among counties sharing Sullivan County's EPA zone, it outranks 10% of them by population. Sullivan County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Sullivan County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). Sullivan County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Next steps for a home in Sullivan County

Mitigation cost doesn't depend on Sullivan 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 Missouri's state radon program

Sullivan County's test kit answers today; a Airthings radon monitor keeps answering for Sullivan 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.