Is Charles Mix County, SD a radon risk area?

EPA places Charles Mix County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Charles Mix County sits at the 75th percentile nationally for radon potential — above 75 of every 100 rated counties.

Charles Mix County by the numbers

About 9,343 people live in Charles Mix County, South Dakota, spread over 1,097.141 square miles. Averaged across its land area, Charles Mix County runs about 9 people per square mile. Rank 785 by population within its EPA zone puts Charles Mix County at the 26th percentile among zone peers. EPA's geology-based Region 8 groups Charles Mix County with 290 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Charles Mix County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. Being in Zone 1 raises the odds Charles Mix County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

Next steps for a home in Charles Mix County

Nothing about Charles Mix 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 Dakota's state radon program

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

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Charles Mix County's numbers. Whatever zone Charles Mix County carries, the zone explainer covers what it does and doesn't tell you about any one house.