Is Fairfield County, SC a radon risk area?

EPA's own radon map rates Fairfield County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Fairfield County sits at the 14th percentile nationally for radon potential — above 14 of every 100 rated counties.

Where Fairfield County sits nationally

About 20,369 people live in Fairfield County, South Carolina, spread over 686.306 square miles. That works out to roughly 30 people per square mile. Rank 608 by population within its EPA zone puts Fairfield County at the 41st percentile among zone peers. EPA's geology-based Region 4 groups Fairfield County with 735 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Fairfield 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 rating means Fairfield 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.

If Fairfield County tests above the action level

Nothing about Fairfield 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

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

More on how this number was built

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