Is Del Norte County, CA a radon risk area?

EPA's own radon map rates Del Norte County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Del Norte County sits at the 16th percentile nationally for radon potential — above 16 of every 100 rated counties.

Del Norte County by the numbers

About 27,009 people live in Del Norte County, California, spread over 1,006.202 square miles. Population density there runs about 27 people per square mile. Rank 518 by population within its EPA zone puts Del Norte County at the 50th percentile among zone peers. Del Norte 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 Del Norte County

At Zone 3, Del Norte County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. A Zone 3 rating means Del Norte County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

If Del Norte County tests above the action level

Nothing about Del Norte 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

Del Norte County's test kit answers today; a Airthings radon monitor keeps answering for Del Norte 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

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