What EPA's radon map says about Modoc County

Modoc County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Rank it against the rest of the country and Modoc County lands in the 5th percentile for radon potential.

Modoc County by the numbers

About 8,491 people live in Modoc County, California, spread over 3,948.233 square miles. Averaged across its land area, Modoc County runs about 2 people per square mile. Among counties sharing Modoc County's EPA zone, it outranks 16% of them by population. Modoc 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 Modoc County

A Zone 3 county like Modoc County is predicted closer to the 0.4 pCi/L typical outdoors than to EPA's 4 pCi/L action level. Don't read Zone 3 as a pass for Modoc County — EPA's guidance to test every home makes no exception for counties predicted low.

Testing and mitigation in Modoc County

Mitigation cost doesn't depend on Modoc 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

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

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.