Short-term kitKidde
442020 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 3 days
Locations and reports
Radon Levels in Yolo County, California
EPA puts Yolo County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 2.1% of 48 (2008 to 2017, laboratory totals) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
2.1%
8.2 pts below CA
- Yolo
- 2.1%
- California
- 10.3%
48 tests, 2008 to 2017
Median result
0.9pCi/L
Below action level
- Yolo
- 0.9 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
48
28th of 33 by tests
- Yolo
- 48
- Los Angeles
- 2,363
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in California
31 of 33
Lowest quarter
- Yolo
- 2.1%
- El Dorado
- 30.3%
By share, of 33 with 30+ tests
Read a result for Yolo County
Starts at Yolo County's median, 0.9 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.9 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Yolo County's median reported result, 2008 to 2017.
The data
Yolo County, At a glance
Yolo 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 Yolo County, 2008 to 2017, laboratory
Under 2 pCi/L: 83%2 to 4 pCi/L: 15%4 pCi/L and above: 2%
Of 48 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 40 | 83.3% |
| 2 to 4 pCi/L | 7 | 14.6% |
| 4 pCi/L and above | 1 | 2.1% |
What these figures count
These are the 48 tests reported to CDC for Yolo 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).
Yolo County, Compared
Yolo County radon figures, compared
Calculated by Radon411Only 1 of 48 radon tests reported for Yolo County over the 2008 to 2017 laboratory totals reached 4 pCi/L (2.1%). The median result, 0.9 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 6.3 pCi/L.
Across 56 California counties pooled together, 10.3% of tests reached that level, so Yolo County runs 8.2 points below its state. Against the national pool of 35.7%, the gap is 33.6 points lower. Its place in the state: 31st of 33 California counties with 30 or more tests for the same period.
Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 2.1% share point the same way here. Of 3 neighbours with a figure, all 3 reported a larger share at or above 4 pCi/L; the spread is 7.7% (Sacramento County) to 15.8% (Solano County).
Below the action level, 40 tests (83.3%) came in under 2 pCi/L, against 76.8% statewide, and 7 tests (14.6%) fell between 2 and 4, against 12.9% statewide. USGS geology rates 100% of the county's land low radon potential.
CDC's ten-year totals for Yolo County went from 46 tests (2005 to 2014) to 48 (2008 to 2017), the share going from 0.0% to 2.1%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Yolo County, Geology
The ground under Yolo County
PredictedUSGS's geologic map puts all of Yolo County's mapped land in one class: low radon potential. The map puts 66.6% of Yolo County in the area it calls Great Valley and 33.4% in Northern Coast Ranges. USGS gives the first a radon index of 8 and the second 6, both in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Great Valley | Quaternary alluvial gravel, sand, silt, clay. | Low | 8 | 66.6% |
| Northern Coast Ranges | Metamorphosed marine sedimentary rocks and ultramafic rocks. | Low | 6 | 33.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Yolo County beside the ground around it
Across California 0.1% of the land is rated high; none of Yolo County's is. Of the 6 counties that border it, 1 has more moderate-potential ground, Sacramento County the most at 20.3%.
The map rates the ground, not the air in any home.
Local help
Yolo County, Local resources
Radon testing and mitigation in Yolo 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
Yolo County, Questions
Questions about radon in Yolo County
Are radon levels high in Yolo County?
Over the 2008 to 2017 laboratory totals, 2.1% of the radon tests reported to CDC for Yolo County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of 33 California counties with 30 or more tests for the same period, 30 reported a higher share; pooled, the state comes to 10.3%.
Which counties border Yolo County?
Yolo County borders 6 counties: Solano County, Napa County, Sutter County, Sacramento County, Colusa County and Lake County.
Products
Yolo County, Products
Testing a home in Yolo County
In Yolo County, 2.1% of 48 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 10.3% pooled across California. 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 Yolo 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
View Radon Wi-Fi radon monitor with an e-paper display
- C-NRPP 2024/25: Approved
- Battery
- Wi-Fi, Bluetooth
- Screen, app
Method: Alpha spectrometry
Readings: Every 60 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Yolo County, Bordering counties
Counties bordering Yolo County
Calculated by Radon411- Radon levels in Sutter CountyEPA zone 3
42.9%at or above 4 pCi/L
Median 1.9 pCi/L · 7 tests · 40.8 points above Yolo County
- Radon levels in Solano CountyEPA zone 3
15.8%at or above 4 pCi/L
Median 0.9 pCi/L · 38 tests · 13.7 points above Yolo County
- Radon levels in Lake CountyEPA zone 3
12.5%at or above 4 pCi/L
Median 0.9 pCi/L · 24 tests · 10.4 points above Yolo County
- Radon levels in Napa CountyEPA zone 3
10.5%at or above 4 pCi/L
Median 0.9 pCi/L · 57 tests · 8.4 points above Yolo County
- Radon levels in Sacramento CountyEPA zone 3
7.7%at or above 4 pCi/L
Median 0.9 pCi/L · 194 tests · 5.6 points above Yolo County
- Radon levels in Colusa CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.2 pCi/L · 1 test · 2.1 points below Yolo County
Yolo County, Cities and towns
Cities and towns in Yolo County
The Census Bureau estimates 224,410 residents in Yolo County for July 1, 2025, 6,650 more than in 2020 (+3.1%). That works out to 221 people per square mile of land. Its largest town, Davis, has 66,110 residents, 29.5% of the total. Together its 4 incorporated places hold 86.0% of those residents; the other 14.0% live outside any of them. CDC's 48 reported tests for 2008 to 2017 work out to 0.2 per 1,000 residents (2025 estimate), close to California's 0.2.
From Davis to Winters, CDC publishes no figure by town: each reads Yolo County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Davis | 66,110 | −1.2% | 29.5% |
| Woodland | 62,513 | +2.5% | 27.9% |
| West Sacramento | 56,216 | +4.5% | 25.1% |
| Winters | 8,214 | +14.2% | 3.7% |
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).
Yolo County, Homes
Homes in Yolo County
Of Yolo County's 81,543 homes, 57% are detached houses, against 57% across California; 23% are in buildings of five or more homes. Half of its homes were built before 1982, close to California's 1976: 17% date from before 1960 and 27% from 2000 or later. 54% 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 | Yolo County | California |
|---|---|---|
| Housing units | 81,543 | 14,532,683 |
| Detached houses | 57% | 57% |
| In buildings of 5 or more | 23% | 24% |
| Mobile homes | 4% | 4% |
| Built before 1960 | 17% | 27% |
| Built since 2000 | 27% | 18% |
| Middle year built | 1982 | 1976 |
| Owner-occupied | 54% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.