Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
Locations and reports
Radon Levels in Modoc County, California
EPA puts Modoc County in Zone 3, its lowest radon zone. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
22.2%
Washoe County
- Washoe
- 22.2%
- Klamath
- 5.3%
2 of 6 neighbours have 30+ tests, 2008 to 2017
Nearest county
11.4%
Butte County, 140 miles
- Butte
- 11.4%
- California
- 10.3%
Share at 4+ pCi/L, 35 tests, 2008 to 2017
Ground above low
44.6%
2.0 pts above California
- Modoc
- 44.6%
- California
- 42.7%
Share of land USGS rates moderate or high potential
Tests reported
0
None published
A home here needs its own test
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 Modoc 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
Modoc County, At a glance
Modoc County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 55% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
No CDC test figures here
CDC has published no radon test figures for Modoc County. Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Washoe County, NV reported the largest share at or above 4 pCi/L, 22.2%, and Klamath County, OR the smallest, 5.3%.
Modoc County, Compared
Modoc County radon figures, compared
Calculated by Radon411CDC's county radon counts over the 2008 to 2017 laboratory totals cover 56 California counties, and Modoc County is not among them: no year's figure and no ten-year laboratory total names it. Pooled across 56 California counties, 10.3% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Washoe County, NV reported the largest share at or above 4 pCi/L, 22.2%, and Klamath County, OR the smallest, 5.3%. Farther out, Butte County (140 miles away) at 11.4%, Nevada County (158 miles away) at 25.0% and Placer County (174 miles away) at 7.4% have figures too. 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 Modoc County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 55% of the county's land low radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Modoc County, Geology
The ground under Modoc County
PredictedUSGS's geologic map splits Modoc County: 55.4% of its land is low radon potential and 44.6% moderate. The map puts 44.6% of Modoc County in the area it calls Northern Basin and Range and 34.7% in Cascade Range, 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 |
|---|---|---|---|---|
| Northern Basin and Range | Precambrian metamorphic rocks, late Precambrian and Paleozoic metamorphosed and unmetamorphosed sedimentary rocks, Mesozoic and Tertiary intrusive rocks, and Tertiary sedimentary and volcanic rocks. | Moderate | 9 | 44.6% |
| Cascade Range | Upper Tertiary and Quaternary extrusive rocks, mainly basalt and lesser andesite and rhyolite. | Low | 8 | 34.7% |
| Modoc Plateau | Tertiary basalt flows, upper Tertiary to Quaternary basalt flows, and lesser amounts of andesite and rhyolite. | Low | 8 | 20.6% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Modoc County beside the ground around it
Across California 0.1% of the land is rated high; none of Modoc County's is. Of the 6 counties that border it, 3 have more moderate-potential ground, Lake County, OR the most at 85.8%.
The map rates the ground, not the air in any home.
Local help
Modoc County, Local resources
Radon testing and mitigation in Modoc 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
Modoc County, Questions
Questions about radon in Modoc County
Are radon levels high in Modoc County?
No CDC testing statistics are published here for Modoc County, California yet. Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Washoe County, NV reported the largest share at or above 4 pCi/L, 22.2%, and Klamath County, OR the smallest, 5.3%.
Which counties border Modoc County?
Modoc County borders 6 counties: Lassen County, CA, Lake County, OR, Washoe County, NV, Shasta County, CA, Siskiyou County, CA and Klamath County, OR.
Products
Modoc County, Products
Testing a home in Modoc County
No CDC figure names Modoc County; the nearest county with one, Butte County (140 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 Modoc 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
MonitorPYZYCKYH
RD17 plug-in radon detector with a rechargeable battery and color screen
- 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
Modoc County, Bordering counties
Counties bordering Modoc County
Calculated by Radon411- Radon levels in Siskiyou County, CAEPA zone 3
25.0%at or above 4 pCi/L
Median 1.1 pCi/L · 8 tests
- Radon levels in Washoe County, NVEPA zone 2
22.2%at or above 4 pCi/L
Median 1.9 pCi/L · 5,046 tests
- Radon levels in Shasta County, CAEPA zone 3
21.7%at or above 4 pCi/L
Median 2.0 pCi/L · 23 tests
- Radon levels in Klamath County, OREPA zone 2
5.3%at or above 4 pCi/L
Median 0.4 pCi/L · 38 tests
- Radon levels in Lassen County, CAEPA zone 3
0.0%at or above 4 pCi/L
Median 1.1 pCi/L · 4 tests
- Radon levels in Lake County, OREPA zone 2
0.0%at or above 4 pCi/L
Median 0.3 pCi/L · 4 tests
Modoc County, Cities and towns
Cities and towns in Modoc County
About 8,426 people live in Modoc County by the Census Bureau's estimate for July 1, 2025, 253 fewer than in 2020 (−2.9%). Spread over its land, that is 2.1 people to the square mile. Alturas, its one incorporated place, has 2,634 residents, 31.3% of the total. CDC publishes no radon test count for Modoc County; across California its counts for 2008 to 2017 come to 0.2 tests for every 1,000 residents (2025 estimate).
Alturas is the one incorporated place here; CDC publishes no figure by town, so it reads Modoc County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Alturas | 2,634 | −2.6% | 31.3% |
One incorporated place, 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).
Modoc County, Homes
Homes in Modoc County
Modoc County is a place of houses on their own lots: 80% of its 4,774 homes are detached single-family houses, against 57% across California. Half of its homes were built before 1976, close to California's 1976: 30% date from before 1960 and 14% from 2000 or later. Owners live in 77% of the occupied homes (California: 56%), so for most households a test and a fix are their own to order.
| Homes | Modoc County | California |
|---|---|---|
| Housing units | 4,774 | 14,532,683 |
| Detached houses | 80% | 57% |
| In buildings of 5 or more | 4% | 24% |
| Mobile homes | 13% | 4% |
| Built before 1960 | 30% | 27% |
| Built since 2000 | 14% | 18% |
| Middle year built | 1976 | 1976 |
| Owner-occupied | 77% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.