Fresno County, CA radon potential

EPA places Fresno 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 Fresno County lands in the 65th percentile for radon potential.

Fresno County by the numbers

Fresno County, California is home to about 1,024,125 people across 5,958.582 square miles. Averaged across its land area, Fresno County runs about 172 people per square mile. Within its own EPA zone, Fresno County is bigger by population than 99% of the counties that share it. Geologically, Fresno County is grouped into EPA Region 9 alongside 94 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

EPA's Zone 2 rating for Fresno County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. Fresno County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Testing and mitigation in Fresno 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 Fresno County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Fresno County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

Where Fresno County's figures come from

Fresno County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Fresno County carries, the zone explainer covers what it does and doesn't tell you about any one house.