Charleston County, SC radon potential

EPA's own radon map rates Charleston County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Charleston County sits at the 31st percentile nationally for radon potential — above 31 of every 100 rated counties.

Where Charleston County sits nationally

Charleston County, South Carolina is home to about 431,001 people across 918.147 square miles. Population density there runs about 469 people per square mile. Within its own EPA zone, Charleston County is bigger by population than 94% of the counties that share it. Geologically, Charleston 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

At Zone 3, Charleston County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. A Zone 3 rating means Charleston County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

Testing and mitigation in Charleston 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 South Carolina's state radon program

For Charleston County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Charleston 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 Charleston County's figures come from

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