Brule County, SD: EPA's radon zone, explained

EPA's own radon map rates Brule County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 71st percentile for radon potential — Brule County outranks 71% of every county EPA has rated.

How Brule County compares

Brule County, South Dakota is home to about 5,261 people across 817.222 square miles. That works out to roughly 6 people per square mile. By population, Brule County is the 915th largest of every county sharing its EPA zone — the 14th percentile by population within that zone. EPA's geology-based Region 8 groups Brule County with 290 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Brule County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Brule County specifically.

If Brule County tests above the action level

For a Brule 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 Brule County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Brule 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 Brule County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.