San Bernardino County, CA radon potential

EPA places San Bernardino County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and San Bernardino County lands in the 66th percentile for radon potential.

Where San Bernardino County sits nationally

San Bernardino County, California is home to about 2,214,281 people across 20,068.42 square miles. Population density there runs about 110 people per square mile. Within its own EPA zone, San Bernardino County is bigger by population than 100% of the counties that share it. Geologically, San Bernardino County is grouped into EPA Region 9 alongside 94 other counties that share its rock and soil setting.

Zone vs. an actual test

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's San Bernardino County's Zone 2 prediction. Nothing about a Zone 2 label lowers the case for testing in San Bernardino County — EPA recommends it in every zone, moderate included.

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

Where San Bernardino County's figures come from

San Bernardino County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.