What EPA's radon map says about Lewis County

Lewis County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Lewis County in the 78th percentile nationally for radon potential — higher than 78% of the counties EPA has rated.

How Lewis County compares

About 13,418 people live in Lewis County, Tennessee, spread over 282.092 square miles. That works out to roughly 48 people per square mile. Among counties sharing Lewis County's EPA zone, it outranks 34% of them by population. EPA's geology-based Region 4 groups Lewis County with 735 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Where the national indoor average runs about 1.3 pCi/L, Lewis County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Being in Zone 1 raises the odds Lewis County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Lewis County tests above the action level

Mitigation cost doesn't depend on Lewis 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 Tennessee's state radon program

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

Lewis County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Lewis County carries, the zone explainer covers what it does and doesn't tell you about any one house.