Smith County, MS: EPA's radon zone, explained

Smith County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. That puts Smith County in the 10th percentile nationally for radon potential — higher than 10% of the counties EPA has rated.

Smith County by the numbers

Smith County, Mississippi is home to about 14,051 people across 636.268 square miles. That works out to roughly 22 people per square mile. By population, Smith County is the 730th largest of every county sharing its EPA zone — the 29th percentile by population within that zone. EPA's geology-based Region 4 groups Smith County with 735 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Smith County

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Smith County's Zone 3 prediction is the low end of the scale. Even at Zone 3, Smith County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

Next steps for a home in Smith County

For a Smith 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 Mississippi's state radon program

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

Where Smith County's figures come from

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