Riverside County, CA radon potential

Riverside 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. Riverside County sits at the 66th percentile nationally for radon potential — above 66 of every 100 rated counties.

Riverside County by the numbers

Riverside County, California is home to about 2,529,933 people across 7,209.021 square miles. That works out to roughly 351 people per square mile. Within its own EPA zone, Riverside County is bigger by population than 100% of the counties that share it. EPA's geology-based Region 9 groups Riverside County with 94 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Riverside 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. A county-wide moderate average, like Riverside County's, can still hide a specific house well above or below it — testing is what actually answers the question.

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

Where Riverside 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 Riverside County carries, the zone explainer covers what it does and doesn't tell you about any one house.