Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
Locations and reports
Radon Levels in Colusa County, California
EPA puts Colusa County in Zone 3, its lowest radon zone, and only 1 radon test from it is 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
11.4%
Butte County
- Butte
- 11.4%
- Yolo
- 2.1%
2 of 5 neighbours have 30+ tests, 2008 to 2017
Nearest county
2.1%
Yolo County, 38 miles
- Yolo
- 2.1%
- California
- 10.3%
Share at 4+ pCi/L, 48 tests, 2008 to 2017
Ground above low
None
42.7 pts below California
- Colusa
- 0.0%
- California
- 42.7%
Share of land USGS rates moderate or high potential
Tests reported
1
Too few for a share
- Colusa
- 1
- 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 Colusa 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
Colusa County, At a glance
Colusa 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 Colusa County, 2008 to 2017, laboratory
CDC holds 1 reported test for Colusa County over the 2008 to 2017 laboratory totals, a result of 0.2 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Colusa County beside the counties around it is how this page reads it.
What these figures count
Only 1 test was reported to CDC for Colusa 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. Measured data period: 2008 to 2017.
Colusa County, Compared
Colusa County radon figures, compared
Calculated by Radon411CDC's largest figure for Colusa County rests on 1 test over the 2008 to 2017 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 100.0 points and no rank or comparison is drawn from it. Results reached as high as 0.2 pCi/L, with a middle value of 0.2 pCi/L.
Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Butte County reported the largest share at or above 4 pCi/L, 11.4%, and Yolo County the smallest, 2.1%. Farther out, Napa County (47 miles away) at 10.5%, Sonoma County (57 miles away) at 0.8% and Solano County (65 miles away) at 15.8% 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 Colusa 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.
Colusa County, Geology
The ground under Colusa County
PredictedUSGS's geologic map puts all of Colusa County's mapped land in one class: low radon potential. The map puts 54.2% of Colusa County in the area it calls Great Valley and 45.8% 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 | 54.2% |
| Northern Coast Ranges | Metamorphosed marine sedimentary rocks and ultramafic rocks. | Low | 6 | 45.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Colusa County beside the ground around it
Across California 0.1% of the land is rated high; none of Colusa County's is. Of the 5 counties that border it, 1 has more moderate-potential ground, Butte County the most at 54.1%.
The map rates the ground, not the air in any home.
Local help
Colusa County, Local resources
Radon testing and mitigation in Colusa 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
Colusa County, Questions
Questions about radon in Colusa County
Are radon levels high in Colusa County?
Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Colusa County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.2 pCi/L. Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Butte County reported the largest share at or above 4 pCi/L, 11.4%, and Yolo County the smallest, 2.1%.
Which counties border Colusa County?
Colusa County borders 5 counties: Sutter County, Lake County, Glenn County, Yolo County and Butte County.
Products
Colusa County, Products
Testing a home in Colusa County
No CDC figure names Colusa County; the nearest county with one, Yolo County (38 miles away), reported 2.1% 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 Colusa 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
RM-65 rechargeable radon detector with a color screen and alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Colusa County, Bordering counties
Counties bordering Colusa 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
- 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 Butte CountyEPA zone 3
11.4%at or above 4 pCi/L
Median 0.8 pCi/L · 35 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 Glenn CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.8 pCi/L · 2 tests
Colusa County, Cities and towns
Cities and towns in Colusa County
Colusa County's population has barely moved since 2020: 21,836 residents on July 1, 2025 against 21,858 then, by the Census Bureau's estimates. That works out to 19 people per square mile of land. Its largest town, Colusa, has 6,519 residents, 29.9% of the total. Together its 2 incorporated places hold 55.2% of those residents; the other 44.8% live outside any of them. Reported testing is thin here: 1 test over 2008 to 2017, or under 0.1 for every 1,000 residents (2025 estimate), where California as a whole comes to 0.2.
From Colusa to Williams, CDC publishes no figure by town: each reads Colusa County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Colusa | 6,519 | +1.7% | 29.9% |
| Williams | 5,529 | −0.3% | 25.3% |
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).
Colusa County, Homes
Homes in Colusa County
Colusa County is a place of houses on their own lots: 81% of its 8,157 homes are detached single-family houses, against 57% across California. Half of its homes were built before 1979, close to California's 1976: 30% date from before 1960 and 25% from 2000 or later. 62% 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 | Colusa County | California |
|---|---|---|
| Housing units | 8,157 | 14,532,683 |
| Detached houses | 81% | 57% |
| In buildings of 5 or more | 4% | 24% |
| Mobile homes | 6% | 4% |
| Built before 1960 | 30% | 27% |
| Built since 2000 | 25% | 18% |
| Middle year built | 1979 | 1976 |
| Owner-occupied | 62% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.