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Radon Levels in Santa Barbara County, California

EPA puts Santa Barbara County in Zone 1, its highest radon zone, and 17.6% of its 421 reported radon tests (2008 to 2017, laboratory totals) were at or above 4 pCi/L. 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

  • Share at 4+ pCi/L

    17.6%

    7.3 pts above CA

    Santa Barbara
    17.6%
    California
    10.3%

    421 tests, 2008 to 2017

  • Median result

    1.2pCi/L

    Below action level

    Santa Barbara
    1.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    421

    7th of 33 by tests

    Santa Barbara
    421
    Los Angeles
    2,363

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in California

    8 of 33

    Top quarter

    Santa Barbara
    17.6%
    El Dorado
    30.3%

    By share, of 33 with 30+ tests

Read a result for Santa Barbara County

Starts at Santa Barbara County's median, 1.2 pCi/L

1.2pCi/L

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

EPA’s reading of 1.2 pCi/L

Below 2 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 below 2 pCi/L, the level at which EPA says a fix should be considered. Santa Barbara County's median reported result, 2008 to 2017.

Interpret this reading

The data

Santa Barbara County, At a glance

Santa Barbara County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Santa Barbara County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: Moderate across 93% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Santa Barbara County, 2008 to 2017, laboratory

Reported results by concentration band, Santa Barbara County, 2008 to 2017, laboratory
Under 2 pCi/L: 66%2 to 4 pCi/L: 17%4 pCi/L and above: 17%

Of 421 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Santa Barbara County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L27765.8%
2 to 4 pCi/L7016.6%
4 pCi/L and above7417.6%
What these figures count

These are the 421 tests reported to CDC for Santa Barbara County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Santa Barbara County, Compared

Santa Barbara County radon figures, compared

Calculated by Radon411

Santa Barbara County's 421 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.2 pCi/L and a maximum of 86.3 pCi/L, and 17.6% reached 4 pCi/L. California as a whole (56 California counties, pooled) comes to 10.3%: 7.3 points lower than here.

Among its state's counties it ranks 8th of 33 California counties with 30 or more tests for the same period. Statewide for the same period, El Dorado County reported the highest share (30.3%) and Sonoma County the lowest (0.8%).

Below the action level, 277 tests (65.8%) came in under 2 pCi/L, against 76.8% statewide, and 70 tests (16.6%) fell between 2 and 4, against 12.9% statewide. CDC's ten-year totals for Santa Barbara County went from 345 tests (2005 to 2014) to 421 (2008 to 2017), the share going from 11.9% to 17.6%.

EPA's 1993 zone map puts Santa Barbara County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 93% of the county's land moderate radon potential.

Next door, the shares run from 11.6% in Kern County to 12.5% in San Luis Obispo County, with San Luis Obispo County, Ventura County and Kern County below Santa Barbara County.

Santa Barbara County against California, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Santa Barbara County
Santa Barbara County42117.6%1.2 pCi/LThis county
California, pooled56 counties, pooled9,41510.3%Not pooled−7.3 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+18.1 points
El Dorado Countyhighest in the state27430.3%1.6 pCi/L+12.7 points
Sonoma Countylowest in the state1310.8%0.5 pCi/L−16.8 points
San Luis Obispo County, CAborders it8012.5%1.0 pCi/L−5.1 points
Ventura County, CAborders it33511.9%1.0 pCi/L−5.7 points
Kern County, CAborders it12111.6%1.8 pCi/L−6.0 points
Where Santa Barbara County's reported results fell, 2008 to 2017, laboratory, beside California and the United States
ResultSanta Barbara County testsSanta Barbara County shareCalifornia shareU.S. shareAgainst California
Under 2 pCi/L27765.8%76.8%39.6%−11.0 points
2 to 4 pCi/L7016.6%12.9%24.7%+3.7 points
4 pCi/L and above7417.6%10.3%35.7%+7.3 points
Santa Barbara County ranked among the 33 California counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Nevada County3 of 3326025.0%2.0 pCi/L
Tulare County4 of 338023.8%1.7 pCi/L
Tuolumne County5 of 337423.0%1.4 pCi/L
Santa Cruz County6 of 3310521.9%1.2 pCi/L
Calaveras County7 of 333417.6%1.7 pCi/L
Santa Barbara County8 of 3342117.6%1.2 pCi/L
Solano County9 of 333815.8%0.9 pCi/L
Monterey County10 of 338714.9%0.8 pCi/L
San Joaquin County11 of 337414.9%1.4 pCi/L
Madera County12 of 333414.7%1.4 pCi/L
San Luis Obispo County13 of 338012.5%1.0 pCi/L
Santa Barbara County ten-year laboratory totals, against California's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestCalifornia, pooledChange from the row before
2008 to 201742117.6%1.2 pCi/L86.3 pCi/L10.3%+0.1 points
2007 to 201639917.5%1.2 pCi/L86.3 pCi/L10.6%+2.1 points
2006 to 201536915.4%1.1 pCi/L86.3 pCi/L10.6%+3.5 points
2005 to 201434511.9%1.0 pCi/L86.3 pCi/L10.0%First on file

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

Santa Barbara County, Geology

The ground under Santa Barbara County

Predicted

Most of the ground under Santa Barbara County is one class on USGS's geologic map: 92.7% of its land is moderate radon potential, with 6.9% low. The map puts 79.9% of Santa Barbara County in the area it calls Southern Coast Ranges and 12.8% in Transverse Ranges, with one smaller area beside them. USGS gives both a radon index of 9, in the moderate band (9 to 11).

USGS's geologic areas under Santa Barbara County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Southern Coast RangesMetamorphosed marine sedimentary rocks, ultramafic rocks, Triasic metamorphic rocks, Mesozoic granitic rocks, and a series of fault-bounded linear basins in which Teriary marine and continental sedimentary rocks were deposited.Moderate979.9%
Transverse RangesPrecambrian metamorphic rocks and Mesozoic granitic rocks, and the western part is underlain by Cretaceous to Pliocene marine sedimentary rocks.Moderate912.8%
Channel IslandsTertiary marine sedimentary, volcanic, igneous, and metamorphic rocks.Low76.9%

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

Santa Barbara County beside the ground around it

Across California 0.1% of the land is rated high; none of Santa Barbara County's is. Of the 3 counties that border it, 2 have more moderate-potential ground, San Luis Obispo County the most at 99.7%.

Share of land by USGS radon potential: Santa Barbara County, the 3 counties bordering it and California
AreaEPA zoneLow potentialModerate potentialHigh potential
Santa Barbara CountyZone 16.9%92.7%None
San Luis Obispo CountyZone 2None99.7%None
Ventura CountyZone 12.0%97.8%None
Kern CountyZone 244.8%55.2%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

Santa Barbara County, Local resources

Radon testing and mitigation in Santa Barbara 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

Santa Barbara County, Questions

Questions about radon in Santa Barbara County

Are radon levels high in Santa Barbara County?

Over the 2008 to 2017 laboratory totals, 17.6% of the radon tests reported to CDC for Santa Barbara County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.2 pCi/L. Of 33 California counties with 30 or more tests for the same period, 7 reported a higher share; pooled, the state comes to 10.3%.

Which counties border Santa Barbara County?

Santa Barbara County borders 3 counties: San Luis Obispo County, Ventura County and Kern County.

Products

Santa Barbara County, Products

Testing a home in Santa Barbara County

In Santa Barbara County, 17.6% of 421 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 10.3% pooled across California. In Zone 1 the year-round level in Santa Barbara County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Santa Barbara County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Santa Barbara County

Explore

Santa Barbara County, Bordering counties

Counties bordering Santa Barbara County

Calculated by Radon411

Santa Barbara County, Cities and towns

Cities and towns in Santa Barbara County

About 442,065 people live in Santa Barbara County by the Census Bureau's estimate for July 1, 2025, 6,260 fewer than in 2020 (−1.4%). That works out to 162 people per square mile of land. Its largest town, Santa Maria, has 111,390 residents, 25.2% of the total. Together its 8 incorporated places hold 69.3% of those residents; the other 30.7% live outside any of them. Testing is reported here more often than across the state: CDC's 421 reported tests for 2008 to 2017 come to 1.0 for every 1,000 residents (2025 estimate), against 0.2 for California.

From Santa Maria to Buellton, CDC publishes no figure by town: each reads Santa Barbara County's.

The cities and towns in Santa Barbara County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Santa Maria111,390+1.5%25.2%
Santa Barbara86,422−2.6%19.5%
Lompoc43,315−2.4%9.8%
Goleta32,401−1.1%7.3%
Carpinteria12,734−3.9%2.9%
Guadalupe8,846+7.0%2.0%
Solvang5,944−2.7%1.3%
Buellton5,158−0.8%1.2%

8 incorporated places, 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).

Santa Barbara County, Homes

Homes in Santa Barbara County

Of Santa Barbara County's 159,766 homes, 57% are detached houses, against 57% across California; 22% are in buildings of five or more homes. Half of its homes were built before 1974, close to California's 1976: 23% date from before 1960 and 14% from 2000 or later. 53% 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 Santa Barbara County, California, 2019 to 2023
HomesSanta Barbara CountyCalifornia
Housing units159,76614,532,683
Detached houses57%57%
In buildings of 5 or more22%24%
Mobile homes5%4%
Built before 196023%27%
Built since 200014%18%
Middle year built19741976
Owner-occupied53%56%

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