Walla Walla County, WA radon potential

Walla Walla County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Walla Walla County sits at the 56th percentile nationally for radon potential — above 56 of every 100 rated counties.

Where Walla Walla County sits nationally

Walla Walla County, Washington is home to about 62,068 people across 1,270.033 square miles. That works out to roughly 49 people per square mile. Within its own EPA zone, Walla Walla County is bigger by population than 71% of the counties that share it. Geologically, Walla Walla County is grouped into EPA Region 10 alongside 141 other counties that share its rock and soil setting.

Zone vs. an actual test

Walla Walla County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Walla Walla County — testing is the only way to know an individual home's actual level.

Next steps for a home in Walla Walla County

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 Washington's state radon program

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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Walla Walla County carries, the zone explainer covers what it does and doesn't tell you about any one house.