Stanislaus County, CA radon potential

EPA places Stanislaus County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 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 Stanislaus County lands in the 31st percentile for radon potential.

Stanislaus County by the numbers

Stanislaus County, California is home to about 556,972 people across 1,496.15 square miles. That works out to roughly 372 people per square mile. Within its own EPA zone, Stanislaus County is bigger by population than 95% of the counties that share it. EPA's geology-based Region 9 groups Stanislaus County with 94 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Stanislaus County's Zone 3 prediction is the low end of the scale. A Zone 3 label describes Stanislaus County's average, not any one basement or slab in it — testing is still the only way an individual homeowner actually finds out.

If Stanislaus County tests above the action level

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

The methodology guide shows exactly which EPA and Census sources feed Stanislaus County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.