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

Pennington County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Pennington County sits at the 60th percentile nationally for radon potential — above 60 of every 100 rated counties.

How Pennington County compares

Pennington County, South Dakota is home to about 115,979 people across 2,776.765 square miles. Population density there runs about 42 people per square mile. By population, Pennington County is the 176th largest of every county sharing its EPA zone — the 83rd percentile by population within that zone. EPA's geology-based Region 8 groups Pennington County with 290 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

EPA's Zone 2 rating for Pennington County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. Nothing about a Zone 2 label lowers the case for testing in Pennington County — EPA recommends it in every zone, moderate included.

If Pennington County tests above the action level

For a Pennington 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 Pennington County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Pennington 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 Pennington 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.