Is Darlington County, SC a radon risk area?

EPA's own radon map rates Darlington County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Darlington County sits at the 24th percentile nationally for radon potential — above 24 of every 100 rated counties.

Where Darlington County sits nationally

About 62,425 people live in Darlington County, South Carolina, spread over 560.629 square miles. Averaged across its land area, Darlington County runs about 111 people per square mile. Rank 295 by population within its EPA zone puts Darlington County at the 71st percentile among zone peers. EPA's geology-based Region 4 groups Darlington County with 735 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Darlington County's predicted average sits below the national indoor average of about 1.3 pCi/L, well under EPA's 4 pCi/L action level. Don't read Zone 3 as a pass for Darlington County — EPA's guidance to test every home makes no exception for counties predicted low.

Testing and mitigation in Darlington County

Nothing about Darlington County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find South Carolina's state radon program

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

Darlington County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.