Bon Homme County, SD: EPA's radon zone, explained

EPA's own radon map rates Bon Homme County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Bon Homme County sits at the 73rd percentile nationally for radon potential — above 73 of every 100 rated counties.

How Bon Homme County compares

Bon Homme County, South Dakota is home to about 7,071 people across 563.549 square miles. Population density there runs about 13 people per square mile. By population, Bon Homme County is the 844th largest of every county sharing its EPA zone — the 21st percentile by population within that zone. EPA's geology-based Region 8 groups Bon Homme County with 290 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Bon Homme County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Bon Homme County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. That doesn't mean every Bon Homme County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

If Bon Homme County tests above the action level

For a Bon Homme County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find South Dakota's state radon program

For Bon Homme County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Bon Homme County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

Where Bon Homme County's figures come from

Bon Homme County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Bon Homme County carries, the zone explainer covers what it does and doesn't tell you about any one house.