What EPA's radon map says about Sumter County

Sumter County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Rank it against the rest of the country and Sumter County lands in the 26th percentile for radon potential.

How Sumter County compares

About 104,776 people live in Sumter County, South Carolina, spread over 665.078 square miles. Population density there runs about 158 people per square mile. Among counties sharing Sumter County's EPA zone, it outranks 80% of them by population. Geologically, Sumter County is grouped into EPA Region 4 alongside 735 other counties that share its rock and soil setting.

What this actually means for a house in Sumter County

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Sumter County's Zone 3 prediction is the low end of the scale. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like Sumter County testing above the action level often enough that skipping a test isn't the safe assumption.

Testing and mitigation in Sumter County

Mitigation cost doesn't depend on Sumter 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 South Carolina's state radon program

Sumter County's test kit answers today; a Airthings radon monitor keeps answering for Sumter County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

Sumter 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.