Johnson County, TN radon potential

EPA places Johnson 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. Johnson County sits at the 45th percentile nationally for radon potential — above 45 of every 100 rated counties.

Where Johnson County sits nationally

Johnson County, Tennessee is home to about 18,506 people across 298.44 square miles. Averaged across its land area, Johnson County runs about 62 people per square mile. Within its own EPA zone, Johnson County is bigger by population than 37% of the counties that share it. Johnson 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 Johnson County

Johnson 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). A county-wide moderate average, like Johnson County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Testing and mitigation in Johnson County

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find Tennessee's state radon program

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

Where Johnson County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Johnson County's numbers. Whatever zone Johnson County carries, the zone explainer covers what it does and doesn't tell you about any one house.