Grainger County, TN: EPA's radon zone, explained

EPA places Grainger County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Grainger County in the 84th percentile nationally for radon potential — higher than 84% of the counties EPA has rated.

Where Grainger County sits nationally

Grainger County, Tennessee is home to about 25,073 people across 280.587 square miles. Population density there runs about 89 people per square mile. By population, Grainger County is the 516th largest of every county sharing its EPA zone — the 52nd percentile by population within that zone. EPA's geology-based Region 4 groups Grainger County with 735 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Grainger County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. Some Grainger County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Grainger County

For a Grainger 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 Tennessee's state radon program

For Grainger County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Grainger County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where Grainger County's figures come from

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