What EPA's radon map says about Clarendon County

Clarendon County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Nationally, Clarendon County ranks higher in radon potential than 18% of rated counties (the 18th percentile).

How Clarendon County compares

About 31,030 people live in Clarendon County, South Carolina, spread over 607.208 square miles. Population density there runs about 51 people per square mile. Among counties sharing Clarendon County's EPA zone, it outranks 54% of them by population. Geologically, Clarendon County is grouped into EPA Region 4 alongside 735 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Clarendon County's Zone 3 prediction undercuts the roughly 1.3 pCi/L most US homes average, nowhere near EPA's 4 pCi/L threshold for recommending mitigation. A Zone 3 label describes Clarendon County's average, not any one basement or slab in it — testing is still the only way an individual homeowner actually finds out.

If Clarendon County tests above the action level

Mitigation cost doesn't depend on Clarendon 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

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

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Clarendon County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.