Slope County, ND radon potential

EPA places Slope 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. Nationally, Slope County ranks higher in radon potential than 66% of rated counties (the 66th percentile).

Where Slope County sits nationally

Slope County, North Dakota is home to about 660 people across 1,215.264 square miles. Population density there runs about 1 people per square mile. Within its own EPA zone, Slope County is bigger by population than 0% of the counties that share it. EPA's geology-based Region 8 groups Slope County with 290 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Slope County

Slope 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 Slope 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 Slope County tests above the action level

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find North Dakota's state radon program

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

Where Slope County's figures come from

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