Richland County, ND: EPA's radon zone, explained
Richland County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Rank it against the rest of the country and Richland County lands in the 80th percentile for radon potential.
Richland County by the numbers
Richland County, North Dakota is home to about 16,658 people across 1,435.674 square miles. That works out to roughly 12 people per square mile. By population, Richland County is the 623rd largest of every county sharing its EPA zone — the 42nd percentile by population within that zone. EPA's geology-based Region 8 groups Richland County with 290 other counties nationally sharing its underlying rock and soil profile.
What this actually means for a house in Richland County
Richland 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. That doesn't mean every Richland 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.
Next steps for a home in Richland County
For a Richland 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 North Dakota's state radon program
For Richland County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Richland County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.
Where Richland County's figures come from
Richland County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.