EPA Radon County Map for SC
The purpose of this map is to assist National, State, and local organizations to target their resources and to implement radon-resistant building codes. This map is not intended to be used to determine if a home in a given zone should be tested for radon. Homes with elevated levels of radon have been found in all three zones. All homes should be tested regardless of geographic location.
Note: As you can see from the above map, Greenville County is the "only" county in South Carolina that has been designated a "Zone 1 county" (averages 4 picocuries or above) However, we have installed radon mitigation systems in homes in ALL other upstate counties (which are Zone 2) and some in Aiken and Richland counties which had "double digit readings". We did 3 systems on one street in West Columbia that each had readings over 20 pCi/l).
This is why the EPA maps are sometimes "misleading". Our experience is that you cannot make "assumptions" about any house! The only SAFE and prudent approach is to get your house tested!