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

EPA's own radon map rates Bonner County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 91st percentile for radon potential — Bonner County outranks 91% of every county EPA has rated.

Bonner County by the numbers

Bonner County, Idaho is home to about 53,955 people across 1,733.229 square miles. Averaged across its land area, Bonner County runs about 31 people per square mile. By population, Bonner County is the 297th largest of every county sharing its EPA zone — the 72nd percentile by population within that zone. Geologically, Bonner County is grouped into EPA Region 10 alongside 141 other counties that share its rock and soil setting.

Zone vs. an actual test

Bonner 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 Bonner County specifically.

Next steps for a home in Bonner County

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

Bonner County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.