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Radon Levels in Del Norte County, California

EPA puts Del Norte County in Zone 3, its lowest radon zone, and only 1 radon test from it is on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Highest bordering

    10.0%

    Josephine County

    Josephine
    10.0%

    1 of 4 neighbours have 30+ tests, 2008 to 2017

  • Nearest county

    11.4%

    Butte County, 187 miles

    Butte
    11.4%
    California
    10.3%

    Share at 4+ pCi/L, 35 tests, 2008 to 2017

  • Ground above low

    None

    42.7 pts below California

    Del Norte
    0.0%
    California
    42.7%

    Share of land USGS rates moderate or high potential

  • Tests reported

    1

    Too few for a share

    Del Norte
    1
    Needed
    30

    2008 to 2017, laboratory

  • EPA radon zone

    Zone 3

    Lower potential

    1. 1
    2. 2
    3. Zone 3

    1 highest, 3 lowest

    EPA predicts under 2 pCi/L indoors

Read a result for Del Norte County

Starts at EPA's action level

4.0pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 4.0 pCi/L

At or above 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.

Interpret this readingWhat a fix costs

The data

Del Norte County, At a glance

Del Norte County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Del Norte County as a whole is an average indoor of less than 2 pCi/L (less than 75 Bq/m³). A low zone clears no address in it: homes above EPA's turn up in all three zones.

USGS geologic potential: Low across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Del Norte County, 2008 to 2017, laboratory

CDC holds 1 reported test for Del Norte County over the 2008 to 2017 laboratory totals, a result of 0.1 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Del Norte County beside the counties around it is how this page reads it.

What these figures count

Only 1 test was reported to CDC for Del Norte County over 2008 to 2017 (laboratory totals), and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.

Measured: CDC tracking data. Measured data period: 2008 to 2017.

How to read these figures

Del Norte County, Compared

Del Norte County radon figures, compared

Calculated by Radon411

CDC's largest figure for Del Norte County rests on 1 test over the 2008 to 2017 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 100.0 points and no rank or comparison is drawn from it. Results reached as high as 0.1 pCi/L, with a middle value of 0.1 pCi/L.

Josephine County, OR, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 10.0% of its tests at or above 4 pCi/L. Farther out, Butte County (187 miles away) at 11.4%, Sonoma County (228 miles away) at 0.8% and Nevada County (236 miles away) at 25.0% have figures too. Pooled across 56 California counties, 10.3% of reported tests reached that level; across every county in the country with a figure, 35.7%.

Statewide for the same period, El Dorado County reported the highest share (30.3%) and Sonoma County the lowest (0.8%). EPA's 1993 map puts Del Norte County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 100% of the county's land low radon potential.

California, the United States and the counties around Del Norte County, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedian
California, pooled56 counties, pooled9,41510.3%Not pooled
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled
El Dorado Countyhighest in the state27430.3%1.6 pCi/L
Sonoma Countylowest in the state1310.8%0.5 pCi/L
Siskiyou County, CAborders it825.0%1.1 pCi/L
Humboldt County, CAborders it2020.0%1.3 pCi/L
Curry County, ORborders it616.7%0.9 pCi/L
Josephine County, ORborders it3010.0%0.7 pCi/L
The nearest California counties to Del Norte County with 30 or more tests, 2008 to 2017, laboratory
CountyDistanceTestsAt or above 4 pCi/LMedian
Butte County187 mi3511.4%0.8 pCi/L
Sonoma County228 mi1310.8%0.5 pCi/L
Nevada County236 mi26025.0%2.0 pCi/L
Yolo County236 mi482.1%0.9 pCi/L
Napa County238 mi5710.5%0.9 pCi/L
Placer County250 mi2837.4%1.1 pCi/L
Marin County261 mi956.3%0.8 pCi/L
Solano County261 mi3815.8%0.9 pCi/L

Pooled shares: Radon411's sum of CDC's county counts for one period.

Del Norte County, Geology

The ground under Del Norte County

Predicted

USGS's geologic map puts all of Del Norte County's mapped land in one class: low radon potential. The map puts 81.9% of Del Norte County in the area it calls Klamath Mountains and 17.9% in Northern Coast Ranges. USGS gives both a radon index of 6, in the low band (5 to 8).

USGS's geologic areas under Del Norte County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Klamath MountainsMetasedimentary and ultramafic metavolcanic rocks, and basalt.Low681.9%
Northern Coast RangesMetamorphosed marine sedimentary rocks and ultramafic rocks.Low617.9%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Del Norte County beside the ground around it

Across California 0.1% of the land is rated high; none of Del Norte County's is. Of the 4 counties that border it, 1 has more moderate-potential ground, Siskiyou County the most at 5.6%.

Share of land by USGS radon potential: Del Norte County, the 4 counties bordering it and California
AreaEPA zoneLow potentialModerate potentialHigh potential
Del Norte CountyZone 399.8%NoneNone
Josephine County, ORZone 3100%NoneNone
Curry County, ORZone 399.7%NoneNone
Humboldt CountyZone 399.3%NoneNone
Siskiyou CountyZone 394.4%5.6%None
California58 counties, pooled by land areaVaries57.2%42.6%0.1%

The map rates the ground, not the air in any home.

Local help

Del Norte County, Local resources

Radon testing and mitigation in Del Norte County

What California's program says
Phone
1-800-745-7236
Email
Radonprogram@cdph.ca.gov
Licensing of radon professionals
The Radon Program certifies all radon service providers operating in California.

What it means

Del Norte County, Questions

Questions about radon in Del Norte County

Are radon levels high in Del Norte County?

Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Del Norte County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.1 pCi/L. Josephine County, OR, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 10.0% of its tests at or above 4 pCi/L.

Which counties border Del Norte County?

Del Norte County borders 4 counties: Josephine County, OR, Curry County, OR, Humboldt County, CA and Siskiyou County, CA.

Products

Del Norte County, Products

Testing a home in Del Norte County

No CDC figure names Del Norte County; the nearest county with one, Butte County (187 miles away), reported 11.4% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Del Norte County.

Test kits and monitors3

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Best radon monitors for Del Norte County homes, compared

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Del Norte County, Bordering counties

Counties bordering Del Norte County

Calculated by Radon411

Del Norte County, Cities and towns

Cities and towns in Del Norte County

About 26,410 people live in Del Norte County by the Census Bureau's estimate for July 1, 2025, 1,209 fewer than in 2020 (−4.4%). That works out to 26 people per square mile of land. Crescent City, its one incorporated place, has 6,002 residents, 22.7% of the total. Reported testing is thin here: 1 test over 2008 to 2017, or under 0.1 for every 1,000 residents (2025 estimate), where California as a whole comes to 0.2.

Crescent City is the one incorporated place here; CDC publishes no figure by town, so it reads Del Norte County's.

Crescent City, Del Norte County: residents on July 1, 2025
PlaceResidentsSince 2020Share of residents
Crescent City6,002−8.2%22.7%

One incorporated place, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Del Norte County, Homes

Homes in Del Norte County

Of Del Norte County's 11,156 homes, 62% are detached houses, against 57% across California; 22% are mobile homes. Half of its homes were built before 1982, close to California's 1976: 22% date from before 1960 and 18% from 2000 or later. 71% of occupied homes are lived in by their owner (California: 56%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Del Norte County, California, 2019 to 2023
HomesDel Norte CountyCalifornia
Housing units11,15614,532,683
Detached houses62%57%
In buildings of 5 or more7%24%
Mobile homes22%4%
Built before 196022%27%
Built since 200018%18%
Middle year built19821976
Owner-occupied71%56%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.