Is Lassen County, CA a radon risk area?

EPA places Lassen 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. Nationally, Lassen County ranks higher in radon potential than 17% of rated counties (the 17th percentile).

How Lassen County compares

About 28,340 people live in Lassen County, California, spread over 4,541.369 square miles. Averaged across its land area, Lassen County runs about 6 people per square mile. Rank 504 by population within its EPA zone puts Lassen County at the 51st percentile among zone peers. Lassen County falls in EPA Radon Region 9, one of 95 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Lassen County

Lassen County's Zone 3 prediction undercuts the roughly 1.3 pCi/L most US homes average, nowhere near EPA's 4 pCi/L threshold for recommending mitigation. Don't read Zone 3 as a pass for Lassen County — EPA's guidance to test every home makes no exception for counties predicted low.

If Lassen County tests above the action level

Nothing about Lassen County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find California's state radon program

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

More on how this number was built

Lassen 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.