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

Clearwater County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Clearwater County in the 75th percentile nationally for radon potential — higher than 75% of the counties EPA has rated.

Clearwater County by the numbers

Clearwater County, Idaho is home to about 9,151 people across 2,457.314 square miles. Averaged across its land area, Clearwater County runs about 4 people per square mile. By population, Clearwater County is the 789th largest of every county sharing its EPA zone — the 26th percentile by population within that zone. EPA's geology-based Region 10 groups Clearwater County with 141 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Clearwater County

Clearwater County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. 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 Clearwater County specifically.

If Clearwater County tests above the action level

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

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