Kootenai County, ID: EPA's radon zone, explained

EPA's own radon map rates Kootenai County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 97th percentile for radon potential — Kootenai County outranks 97% of every county EPA has rated.

How Kootenai County compares

Kootenai County, Idaho is home to about 188,323 people across 1,237.793 square miles. Population density there runs about 152 people per square mile. By population, Kootenai County is the 103rd largest of every county sharing its EPA zone — the 90th percentile by population within that zone. Kootenai County falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Kootenai 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. 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 Kootenai County specifically.

Testing and mitigation in Kootenai County

For a Kootenai 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 Idaho's state radon program

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

The methodology guide shows exactly which EPA and Census sources feed Kootenai County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.