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 Glenn County, California
EPA puts Glenn County in Zone 3, its lowest radon zone, and only 2 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
11.4%
Butte County
- Butte
- 11.4%
1 of 5 neighbours have 30+ tests, 2008 to 2017
Nearest county
11.4%
Butte County, 42 miles
- Butte
- 11.4%
- California
- 10.3%
Share at 4+ pCi/L, 35 tests, 2008 to 2017
Ground above low
None
42.7 pts below California
- Glenn
- 0.0%
- California
- 42.7%
Share of land USGS rates moderate or high potential
Tests reported
2
Too few for a share
- Glenn
- 2
- 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 Glenn 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
Glenn County, At a glance
Glenn 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 Glenn County, 2008 to 2017, laboratory
CDC holds 2 reported tests for Glenn County over the 2008 to 2017 laboratory totals, with a median of 2.8 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Glenn County beside the counties around it is how this page reads it.
What these figures count
Only 2 tests were reported to CDC for Glenn 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).
Glenn County, Compared
Glenn County radon figures, compared
Calculated by Radon411CDC's largest figure for Glenn County rests on 2 tests over the 2008 to 2017 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 50.0 points and no rank or comparison is drawn from it. Results reached as high as 2.9 pCi/L, with a middle value of 2.8 pCi/L.
Butte County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 11.4% of its tests at or above 4 pCi/L. Farther out, Yolo County (68 miles away) at 2.1%, Napa County (75 miles away) at 10.5% and Sonoma County (78 miles away) at 0.8% 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 Glenn 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.
Glenn County, Geology
The ground under Glenn County
PredictedUSGS's geologic map puts all of Glenn County's mapped land in one class: low radon potential. The map puts 59.2% of Glenn County in the area it calls Northern Coast Ranges and 40.4% in Great Valley. USGS gives the first a radon index of 6 and the second 8, both 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 | 59.2% |
| Great Valley | Quaternary alluvial gravel, sand, silt, clay. | Low | 8 | 40.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Glenn County beside the ground around it
Across California 0.1% of the land is rated high; none of Glenn County's is. Of the 5 counties that border it, 2 have more moderate-potential ground, Butte County the most at 54.1%.
The map rates the ground, not the air in any home.
Local help
Glenn County, Local resources
Radon testing and mitigation in Glenn 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
Glenn County, Questions
Questions about radon in Glenn County
Are radon levels high in Glenn County?
Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Glenn County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.8 pCi/L. Butte County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 11.4% of its tests at or above 4 pCi/L.
Which counties border Glenn County?
Glenn County borders 5 counties: Colusa County, Lake County, Tehama County, Butte County and Mendocino County.
Products
Glenn County, Products
Testing a home in Glenn County
No CDC figure names Glenn County; the nearest county with one, Butte County (42 miles away), reported 11.4% 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 Glenn 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
MonitorAranet
Radon One battery digital radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Alarm
- Screen, app
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
Glenn County, Bordering counties
Counties bordering Glenn County
Calculated by Radon411- 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 Colusa CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.2 pCi/L · 1 test
- 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 Mendocino CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.7 pCi/L · 11 tests
Glenn County, Cities and towns
Cities and towns in Glenn County
About 28,141 people live in Glenn County by the Census Bureau's estimate for July 1, 2025, 748 fewer than in 2020 (−2.6%). That works out to 21 people per square mile of land. Its largest town, Orland, has 8,381 residents, 29.8% of the total. Together its 2 incorporated places hold 51.5% of those residents; the other 48.5% live outside any of them. Reported testing is thin here: 2 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 Orland to Willows, CDC publishes no figure by town: each reads Glenn County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Orland | 8,381 | +0.7% | 29.8% |
| Willows | 6,116 | −2.5% | 21.7% |
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).
Glenn County, Homes
Homes in Glenn County
Of Glenn County's 10,973 homes, 70% are detached houses, against 57% across California; 13% are in buildings of five or more homes. Half of its homes were built before 1978, close to California's 1976: 27% 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 | Glenn County | California |
|---|---|---|
| Housing units | 10,973 | 14,532,683 |
| Detached houses | 70% | 57% |
| In buildings of 5 or more | 13% | 24% |
| Mobile homes | 13% | 4% |
| Built before 1960 | 27% | 27% |
| Built since 2000 | 19% | 18% |
| Middle year built | 1978 | 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.