What EPA's radon map says about Glenn County

EPA places Glenn 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 Glenn County lands in the 17th percentile for radon potential.

How Glenn County compares

About 28,304 people live in Glenn County, California, spread over 1,313.94 square miles. Population density there runs about 22 people per square mile. Among counties sharing Glenn County's EPA zone, it outranks 51% of them by population. EPA's geology-based Region 9 groups Glenn County with 94 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Glenn County

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Glenn County's Zone 3 prediction is the low end of the scale. Even at Zone 3, Glenn County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

Next steps for a home in Glenn County

Mitigation cost doesn't depend on Glenn County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find California's state radon program

Glenn County's test kit answers today; a Airthings radon monitor keeps answering for Glenn County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

Glenn County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.