Is Sullivan County, TN a radon risk area?

Sullivan County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Sullivan County sits at the 96th percentile nationally for radon potential — above 96 of every 100 rated counties.

How Sullivan County compares

About 162,703 people live in Sullivan County, Tennessee, spread over 413.545 square miles. Population density there runs about 393 people per square mile. Rank 123 by population within its EPA zone puts Sullivan County at the 89th percentile among zone peers. Sullivan County falls in EPA Radon Region 4, one of 736 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Sullivan County

Sullivan County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Sullivan County specifically.

Testing and mitigation in Sullivan County

Nothing about Sullivan County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Tennessee'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. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

Sullivan County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.