Ada County, ID radon potential

EPA's own radon map rates Ada County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Nationally, Ada County ranks higher in radon potential than 65% of rated counties (the 65th percentile).

How Ada County compares

Ada County, Idaho is home to about 535,799 people across 1,052.252 square miles. Population density there runs about 509 people per square mile. Within its own EPA zone, Ada County is bigger by population than 96% of the counties that share it. EPA's geology-based Region 10 groups Ada County with 141 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Ada County's Zone 2 prediction clears the 1.3 pCi/L national indoor average without reaching EPA's own 4 pCi/L point for recommending a fix. Ada County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Next steps for a home in Ada 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 Idaho's state radon program

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

Where Ada County's figures come from

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