Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Lake County, California
EPA puts Lake County in Zone 3, its lowest radon zone, and only 24 radon tests from it are 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
Highest bordering
10.5%
Napa County
- Napa
- 10.5%
- Sonoma
- 0.8%
3 of 6 neighbours have 30+ tests, 2008 to 2017
Nearest county
0.8%
Sonoma County, 40 miles
- Sonoma
- 0.8%
- California
- 10.3%
Share at 4+ pCi/L, 131 tests, 2008 to 2017
Ground above low
None
42.7 pts below California
- Lake
- 0.0%
- California
- 42.7%
Share of land USGS rates moderate or high potential
Tests reported
26
Too few for a share
- Lake
- 26
- Needed
- 30
2007 to 2016, laboratory
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Read a result for Lake County
Starts at EPA's action level
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
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 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.
The data
Lake County, At a glance
Lake County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
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 Lake County, 2008 to 2017, laboratory
CDC holds 24 reported tests for Lake County over the 2008 to 2017 laboratory totals, with a median of 0.9 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Lake County beside the counties around it is how this page reads it.
What these figures count
Only 24 tests were reported to CDC for Lake 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. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Lake County, Compared
Lake County radon figures, compared
Calculated by Radon411CDC's largest figure for Lake County rests on 26 tests over the 2007 to 2016 laboratory totals, 3 of them at or above 4 pCi/L, so each test moves its share by 3.8 points and no rank or comparison is drawn from it. Results reached as high as 13.1 pCi/L, with a middle value of 1.0 pCi/L.
Of the counties bordering it, 3 have a figure over the 2008 to 2017 laboratory totals: Napa County reported the largest share at or above 4 pCi/L, 10.5%, and Sonoma County the smallest, 0.8%, with Yolo County at 2.1% between. Farther out, Marin County (71 miles away) at 6.3%, Solano County (72 miles away) at 15.8% and Butte County (73 miles away) at 11.4% 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 Lake 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.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Lake County, Geology
The ground under Lake County
PredictedUSGS's geologic map puts all of Lake County's mapped land in one class: low radon potential. All of it lies in the area the map calls Northern Coast Ranges, to which USGS gives a radon index of 6, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Northern Coast Ranges | Metamorphosed marine sedimentary rocks and ultramafic rocks. | Low | 6 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Lake County beside the ground around it
Across California 0.1% of the land is rated high; none of Lake County's is. None of the 6 counties that border it has any moderate-potential ground either.
The map rates the ground, not the air in any home.
Local help
Lake County, Local resources
Radon testing and mitigation in Lake County
- California Indoor Radon ProgramCalifornia Indoor Radon Program, run by California Department of Public Health, licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in California.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Discounted test kits can be purchased through our partner laboratory, Alpha Energy, for $14.95.
- Compare kits
- Professionals in California4 professionals are listed in California.
What California's program says
- Phone
- 1-800-745-7236
- Radonprogram@cdph.ca.gov
- Licensing of radon professionals
The Radon Program certifies all radon service providers operating in California.
What it means
Lake County, Questions
Questions about radon in Lake County
Are radon levels high in Lake County?
Over the 2008 to 2017 laboratory totals, 12.5% of the radon tests reported to CDC for Lake County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of the counties bordering it, 3 have a figure over the 2008 to 2017 laboratory totals: Napa County reported the largest share at or above 4 pCi/L, 10.5%, and Sonoma County the smallest, 0.8%, with Yolo County at 2.1% between.
Which counties border Lake County?
Lake County borders 6 counties: Colusa County, Glenn County, Mendocino County, Sonoma County, Napa County and Yolo County.
Products
Lake County, Products
Testing a home in Lake County
No CDC figure names Lake County; the nearest county with one, Sonoma County (40 miles away), reported 0.8% 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 Lake County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Monitor
Hello Radon C battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Lake County, Bordering counties
Counties bordering Lake County
Calculated by Radon411- Radon levels in Napa CountyEPA zone 3
10.5%at or above 4 pCi/L
Median 0.9 pCi/L · 57 tests
- Radon levels in Yolo CountyEPA zone 3
2.1%at or above 4 pCi/L
Median 0.9 pCi/L · 48 tests
- Radon levels in Sonoma CountyEPA zone 3
0.8%at or above 4 pCi/L
Median 0.5 pCi/L · 131 tests
- Radon levels in Colusa CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.2 pCi/L · 1 test
- Radon levels in Glenn CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.8 pCi/L · 2 tests
- Radon levels in Mendocino CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.7 pCi/L · 11 tests
Lake County, Cities and towns
Cities and towns in Lake County
About 67,772 people live in Lake County by the Census Bureau's estimate for July 1, 2025, 436 fewer than in 2020 (−0.6%). That works out to 54 people per square mile of land. Its largest town, Clearlake, has 16,893 residents, 24.9% of the total. Together its 2 incorporated places hold 32.4% of those residents; the other 67.6% live outside any of them. Testing is reported here more often than across the state: CDC's 26 reported tests for 2007 to 2016 come to 0.4 for every 1,000 residents (2025 estimate), against 0.3 for California.
From Clearlake to Lakeport, CDC publishes no figure by town: each reads Lake County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Clearlake | 16,893 | +1.2% | 24.9% |
| Lakeport | 5,059 | +0.6% | 7.5% |
2 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).
Lake County, Homes
Homes in Lake County
Of Lake County's 34,271 homes, 70% are detached houses, against 57% across California; 20% are mobile homes. Half of its homes were built before 1980, close to California's 1976: 17% date from before 1960 and 20% 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 | Lake County | California |
|---|---|---|
| Housing units | 34,271 | 14,532,683 |
| Detached houses | 70% | 57% |
| In buildings of 5 or more | 5% | 24% |
| Mobile homes | 20% | 4% |
| Built before 1960 | 17% | 27% |
| Built since 2000 | 20% | 18% |
| Middle year built | 1980 | 1976 |
| Owner-occupied | 71% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.