Placer County, CA radon potential

Placer 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. Nationally that's the 64th percentile for radon potential — Placer County outranks 64% of every county EPA has rated.

Placer County by the numbers

Placer County, California is home to about 433,822 people across 1,407.401 square miles. That works out to roughly 308 people per square mile. Within its own EPA zone, Placer County is bigger by population than 94% of the counties that share it. Geologically, Placer County is grouped into EPA Region 9 alongside 94 other counties that share its rock and soil setting.

What this actually means for a house in Placer County

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Placer County's Zone 2 prediction lands in the gap between the two. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Placer County — testing is the only way to know an individual home's actual level.

Next steps for a home in Placer 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 California's state radon program

For Placer County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Placer 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 Placer 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.