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 Butte County, California
EPA puts Butte County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 11.4% of 35 (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
11.4%
1.1 pts above CA
- Butte
- 11.4%
- California
- 10.3%
35 tests, 2008 to 2017
Median result
0.8pCi/L
Below action level
- Butte
- 0.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
35
31st of 33 by tests
- Butte
- 35
- 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
16 of 33
Middle half
- Butte
- 11.4%
- El Dorado
- 30.3%
By share, of 33 with 30+ tests
Read a result for Butte County
Starts at Butte County's median, 0.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.8 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. Butte County's median reported result, 2008 to 2017.
The data
Butte County, At a glance
Butte County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Moderate across 54% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Butte County, 2008 to 2017, laboratory
Under 2 pCi/L: 74%2 to 4 pCi/L: 14%4 pCi/L and above: 12%
Of 35 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 26 | 74.3% |
| 2 to 4 pCi/L | 5 | 14.3% |
| 4 pCi/L and above | 4 | 11.4% |
What these figures count
These are the 35 tests reported to CDC for Butte 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).
Butte County, Compared
Butte County radon figures, compared
Calculated by Radon41111.4% of its 35 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 1.1 points above the 10.3% pooled from 56 California counties.
Ordered from highest share down, it comes 16th of 33 California counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Butte County sits 24.3 points below it.
Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 11.4% share point the same way here.
Half the tests came in under 0.8 pCi/L and half over it; the single highest reached 10.8 pCi/L. The rest split 74.3% under 2 pCi/L and 14.3% from 2 to 4 (California: 76.8% and 12.9%).
CDC's ten-year totals for Butte County went from 33 tests (2005 to 2014) to 35 (2008 to 2017), the share going from 12.1% to 11.4%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Butte County, Geology
The ground under Butte County
PredictedUSGS's geologic map splits Butte County: 54.1% of its land is moderate radon potential and 45.9% low. The map puts 54.1% of Butte County in the area it calls Sierra Nevada and 32.6% in Great Valley, with one smaller area beside them. USGS gives the first a radon index of 9, in the moderate band (9 to 11), and the second 8, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Sierra Nevada | Northern Sierra Nevada is underlain primarily by Paleozoic and Mesozoic metamorphic rocks. Granitic rocks predominate in the southern Sierrra Nevada , with lesser Mesozoic metamorphic rocks. | Moderate | 9 | 54.1% |
| Great Valley | Quaternary alluvial gravel, sand, silt, clay. | Low | 8 | 32.6% |
| Cascade Range | Upper Tertiary and Quaternary extrusive rocks, mainly basalt and lesser andesite and rhyolite. | Low | 8 | 13.2% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Butte County beside the ground around it
Across California 0.1% of the land is rated high; none of Butte County's is. Of the 6 counties that border it, 2 have more moderate-potential ground, Plumas County the most at 84.3%.
The map rates the ground, not the air in any home.
Local help
Butte County, Local resources
Radon testing and mitigation in Butte 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
Butte County, Questions
Questions about radon in Butte County
Are radon levels high in Butte County?
Over the 2008 to 2017 laboratory totals, 11.4% of the radon tests reported to CDC for Butte County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.8 pCi/L. Of 33 California counties with 30 or more tests for the same period, 15 reported a higher share; pooled, the state comes to 10.3%.
Which counties border Butte County?
Butte County borders 6 counties: Yuba County, Tehama County, Glenn County, Plumas County, Sutter County and Colusa County.
Products
Butte County, Products
Testing a home in Butte County
In Butte County, 11.4% of 35 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 Butte 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
EcoBlu plug-in digital radon monitor with a display
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Butte County, Bordering counties
Counties bordering Butte 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 · 31.5 points above Butte County
- Radon levels in Plumas CountyEPA zone 2
38.1%at or above 4 pCi/L
Median 2.1 pCi/L · 21 tests · 26.7 points above Butte County
- Radon levels in Yuba CountyEPA zone 2
0.0%at or above 4 pCi/L
Median 0.1 pCi/L · 7 tests · 11.4 points below Butte County
- Radon levels in Tehama CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.2 pCi/L · 6 tests · 11.4 points below Butte County
- Radon levels in Glenn CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.8 pCi/L · 2 tests · 11.4 points below Butte County
- Radon levels in Colusa CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.2 pCi/L · 1 test · 11.4 points below Butte County
Butte County, Cities and towns
Cities and towns in Butte County
Butte County's population has barely moved since 2020: 209,211 residents on July 1, 2025 against 210,204 then, by the Census Bureau's estimates. That works out to 128 people per square mile of land. Chico alone is home to 105,081 of them, 50.2% of the total. Together its 5 incorporated places hold 69.2% of those residents; the other 30.8% live outside any of them. CDC's 35 reported tests for 2008 to 2017 work out to 0.2 per 1,000 residents (2025 estimate), close to California's 0.2.
From Chico to Biggs, CDC publishes no figure by town: each reads Butte County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Chico | 105,081 | +1.0% | 50.2% |
| Oroville | 20,451 | +2.1% | 9.8% |
| Paradise | 10,023 | +96.9% | 4.8% |
| Gridley | 7,258 | −2.0% | 3.5% |
| Biggs | 1,927 | −2.5% | 0.9% |
5 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).
Butte County, Homes
Homes in Butte County
Of Butte County's 91,176 homes, 61% are detached houses, against 57% across California; 15% are in buildings of five or more homes. Half of its homes were built before 1980, close to California's 1976: 21% date from before 1960 and 21% from 2000 or later. 58% 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 | Butte County | California |
|---|---|---|
| Housing units | 91,176 | 14,532,683 |
| Detached houses | 61% | 57% |
| In buildings of 5 or more | 15% | 24% |
| Mobile homes | 11% | 4% |
| Built before 1960 | 21% | 27% |
| Built since 2000 | 21% | 18% |
| Middle year built | 1980 | 1976 |
| Owner-occupied | 58% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.