Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
Locations and reports
Radon Levels in Mendocino County, California
EPA puts Mendocino County in Zone 3, its lowest radon zone, and only 11 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
0.8%
Sonoma County
- Sonoma
- 0.8%
1 of 6 neighbours have 30+ tests, 2008 to 2017
Nearest county
0.8%
Sonoma County, 69 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
- Mendocino
- 0.0%
- California
- 42.7%
Share of land USGS rates moderate or high potential
Tests reported
11
Too few for a share
- Mendocino
- 11
- Needed
- 30
2008 to 2017, 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 Mendocino 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
Mendocino County, At a glance
Mendocino 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 Mendocino County, 2008 to 2017, laboratory
CDC holds 11 reported tests for Mendocino County over the 2008 to 2017 laboratory totals, with a median of 0.7 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Mendocino County beside the counties around it is how this page reads it.
What these figures count
Only 11 tests were reported to CDC for Mendocino 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).
Mendocino County, Compared
Mendocino County radon figures, compared
Calculated by Radon411CDC's largest figure for Mendocino County rests on 11 tests over the 2008 to 2017 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 9.1 points and no rank or comparison is drawn from it. Results reached as high as 2.3 pCi/L, with a middle value of 0.7 pCi/L.
Sonoma County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 0.8% of its tests at or above 4 pCi/L. Farther out, Napa County (86 miles away) at 10.5%, Yolo County (96 miles away) at 2.1% and Butte County (97 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 Mendocino 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.
Mendocino County, Geology
The ground under Mendocino County
PredictedUSGS's geologic map puts all of Mendocino 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.
Mendocino County beside the ground around it
Across California 0.1% of the land is rated high; none of Mendocino County's is. Of the 6 counties that border it, 1 has more moderate-potential ground, Tehama County the most at 0.2%.
The map rates the ground, not the air in any home.
Local help
Mendocino County, Local resources
Radon testing and mitigation in Mendocino 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
Mendocino County, Questions
Questions about radon in Mendocino County
Are radon levels high in Mendocino County?
Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Mendocino County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.7 pCi/L. Sonoma County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 0.8% of its tests at or above 4 pCi/L.
Which counties border Mendocino County?
Mendocino County borders 6 counties: Lake County, Glenn County, Sonoma County, Tehama County, Trinity County and Humboldt County.
Products
Mendocino County, Products
Testing a home in Mendocino County
No CDC figure names Mendocino County; the nearest county with one, Sonoma County (69 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 Mendocino County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Monitor
RM-63Pro rechargeable radon monitor with a touchscreen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Mendocino County, Bordering counties
Counties bordering Mendocino County
Calculated by Radon411- Radon levels in Humboldt CountyEPA zone 3
20.0%at or above 4 pCi/L
Median 1.3 pCi/L · 20 tests
- Radon levels in Lake CountyEPA zone 3
12.5%at or above 4 pCi/L
Median 0.9 pCi/L · 24 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 Glenn CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.8 pCi/L · 2 tests
- Radon levels in Tehama CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.2 pCi/L · 6 tests
- Radon levels in Trinity CountyEPA zone 3
No CDC figure for 2008 to 2017; its page reads it against its own neighbours.
Mendocino County, Cities and towns
Cities and towns in Mendocino County
About 88,122 people live in Mendocino County by the Census Bureau's estimate for July 1, 2025, 3,226 fewer than in 2020 (−3.5%). That works out to 25 people per square mile of land. No town dominates: Ukiah, the largest, has 16,068 residents, 18.2% of the total. Together its 4 incorporated places hold 32.0% of those residents; the other 68.0% live outside any of them. Reported testing is thin here: 11 tests over 2008 to 2017, or 0.1 for every 1,000 residents (2025 estimate), where California as a whole comes to 0.2.
From Ukiah to Point Arena, CDC publishes no figure by town: each reads Mendocino County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Ukiah | 16,068 | −2.9% | 18.2% |
| Fort Bragg | 6,946 | −0.4% | 7.9% |
| Willits | 4,760 | −4.4% | 5.4% |
| Point Arena | 453 | −1.9% | 0.5% |
4 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).
Mendocino County, Homes
Homes in Mendocino County
Of Mendocino County's 41,495 homes, 73% are detached houses, against 57% across California; 10% are mobile homes. Half of its homes were built before 1977, close to California's 1976: 26% date from before 1960 and 13% from 2000 or later. 61% 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 | Mendocino County | California |
|---|---|---|
| Housing units | 41,495 | 14,532,683 |
| Detached houses | 73% | 57% |
| In buildings of 5 or more | 8% | 24% |
| Mobile homes | 10% | 4% |
| Built before 1960 | 26% | 27% |
| Built since 2000 | 13% | 18% |
| Middle year built | 1977 | 1976 |
| Owner-occupied | 61% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.