Short-term kit
Radon Short Term Test Kit short-term charcoal radon test kit, lab fee included
- Lab fee included
Method: Charcoal
In home: 2 to 7 days
Locations and reports
Radon Levels in Solano County, California
EPA puts Solano County in Zone 3, its lowest radon zone, and 15.8% of its 38 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
Share at 4+ pCi/L
15.8%
5.5 pts above CA
- Solano
- 15.8%
- California
- 10.3%
38 tests, 2008 to 2017
Median result
0.9pCi/L
Below action level
- Solano
- 0.9 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
38
29th of 33 by tests
- Solano
- 38
- 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
9 of 33
Middle half
- Solano
- 15.8%
- El Dorado
- 30.3%
By share, of 33 with 30+ tests
Read a result for Solano County
Starts at Solano 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. Solano County's median reported result, 2008 to 2017.
The data
Solano County, At a glance
Solano County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 94% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Solano County, 2008 to 2017, laboratory
Under 2 pCi/L: 76%2 to 4 pCi/L: 8%4 pCi/L and above: 16%
Of 38 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 29 | 76.3% |
| 2 to 4 pCi/L | 3 | 7.9% |
| 4 pCi/L and above | 6 | 15.8% |
What these figures count
These are the 38 tests reported to CDC for Solano 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).
Solano County, Compared
Solano County radon figures, compared
Calculated by Radon411Solano County's 38 reported tests over the 2008 to 2017 laboratory totals had a middle value of 0.9 pCi/L and a maximum of 6.7 pCi/L, and 15.8% reached 4 pCi/L. California as a whole (56 California counties, pooled) comes to 10.3%: 5.5 points lower than here.
Among its state's counties it ranks 9th 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, 29 tests (76.3%) came in under 2 pCi/L, against 76.8% statewide, and 3 tests (7.9%) fell between 2 and 4, against 12.9% statewide. CDC's ten-year totals for Solano County went from 48 tests (2005 to 2014) to 38 (2008 to 2017), the share going from 0.0% to 15.8%.
EPA's 1993 zone map puts Solano County in Zone 3, a predicted county average under 2 pCi/L. USGS geology rates 94% of the county's land low radon potential.
Next door, the shares run from 0.8% in Sonoma County to 10.5% in Napa County, with Napa County, Contra Costa County and Sacramento County below Solano County.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Solano County, Geology
The ground under Solano County
PredictedUSGS's geologic map puts all of Solano County's mapped land in one class: low radon potential. The map puts 54.6% of Solano County in the area it calls Great Valley and 39.6% 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 | 54.6% |
| Northern Coast Ranges | Metamorphosed marine sedimentary rocks and ultramafic rocks. | Low | 6 | 39.6% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Solano County beside the ground around it
Across California 0.1% of the land is rated high; none of Solano County's is. Of the 5 counties that border it, 2 have more moderate-potential ground, Contra Costa County the most at 74.1%.
The map rates the ground, not the air in any home.
Local help
Solano County, Local resources
Radon testing and mitigation in Solano 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
Solano County, Questions
Questions about radon in Solano County
Are radon levels high in Solano County?
Over the 2008 to 2017 laboratory totals, 15.8% of the radon tests reported to CDC for Solano 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, 8 reported a higher share; pooled, the state comes to 10.3%.
Which counties border Solano County?
Solano County borders 5 counties: Yolo County, Contra Costa County, Napa County, Sacramento County and Sonoma County.
Products
Solano County, Products
Testing a home in Solano County
In Solano County, 15.8% of 38 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 Solano 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
MonitorINKBIRD
INK-RD3 battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Solano County, Bordering counties
Counties bordering Solano 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 · 5.3 points below Solano County
- Radon levels in Contra Costa CountyEPA zone 2
8.8%at or above 4 pCi/L
Median 0.9 pCi/L · 285 tests · 7.0 points below Solano County
- Radon levels in Sacramento CountyEPA zone 3
7.7%at or above 4 pCi/L
Median 0.9 pCi/L · 194 tests · 8.1 points below Solano County
- Radon levels in Yolo CountyEPA zone 3
2.1%at or above 4 pCi/L
Median 0.9 pCi/L · 48 tests · 13.7 points below Solano County
- Radon levels in Sonoma CountyEPA zone 3
0.8%at or above 4 pCi/L
Median 0.5 pCi/L · 131 tests · 15.0 points below Solano County
Solano County, Cities and towns
Cities and towns in Solano County
The Census Bureau estimates 455,376 residents in Solano County for July 1, 2025, 2,481 more than in 2020 (+0.5%). That works out to 554 people per square mile of land. Its largest town, Vallejo, has 123,287 residents, 27.1% of the total. Together its 7 incorporated places hold 96.0% of those residents; the other 4.0% live outside any of them. Reported testing is thin here: 38 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 Vallejo to Rio Vista, CDC publishes no figure by town: each reads Solano County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Vallejo | 123,287 | −2.1% | 27.1% |
| Fairfield | 122,489 | +2.2% | 26.9% |
| Vacaville | 103,850 | +1.7% | 22.8% |
| Suisun City | 29,454 | −0.1% | 6.5% |
| Benicia | 26,401 | −2.6% | 5.8% |
| Dixon | 21,116 | +8.5% | 4.6% |
| Rio Vista | 10,523 | +5.1% | 2.3% |
7 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).
Solano County, Homes
Homes in Solano County
Of Solano County's 163,455 homes, 71% are detached houses, against 57% across California; 14% 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 19% from 2000 or later. 63% 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 | Solano County | California |
|---|---|---|
| Housing units | 163,455 | 14,532,683 |
| Detached houses | 71% | 57% |
| In buildings of 5 or more | 14% | 24% |
| Mobile homes | 3% | 4% |
| Built before 1960 | 17% | 27% |
| Built since 2000 | 19% | 18% |
| Middle year built | 1982 | 1976 |
| Owner-occupied | 63% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.