Union County, SC radon potential

Union County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Nationally that's the 16th percentile for radon potential — Union County outranks 16% of every county EPA has rated.

Where Union County sits nationally

Union County, South Carolina is home to about 26,678 people across 513.604 square miles. That works out to roughly 52 people per square mile. Within its own EPA zone, Union County is bigger by population than 50% of the counties that share it. EPA's geology-based Region 4 groups Union County with 735 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Union County

At Zone 3, Union 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 Union 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.

Next steps for a home in Union 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 Union County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Union 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 Union County's figures come from

Union 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.