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 Madera County, California
EPA puts Madera County in Zone 2, its middle radon zone, and most reported tests there come back low, though 14.7% of 34 (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
14.7%
4.4 pts above CA
- Madera
- 14.7%
- California
- 10.3%
34 tests, 2008 to 2017
Median result
1.4pCi/L
Below action level
- Madera
- 1.4 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
34
33rd of 33 by tests
- Madera
- 34
- Los Angeles
- 2,363
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in California
12 of 33
Middle half
- Madera
- 14.7%
- El Dorado
- 30.3%
By share, of 33 with 30+ tests
Read a result for Madera County
Starts at Madera County's median, 1.4 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.4 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. Madera County's median reported result, 2008 to 2017.
The data
Madera County, At a glance
Madera County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Madera County is a
USGS geologic potential: Moderate across 63% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Madera County, 2008 to 2017, laboratory
Under 2 pCi/L: 68%2 to 4 pCi/L: 17%4 pCi/L and above: 15%
Of 34 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 23 | 67.6% |
| 2 to 4 pCi/L | 6 | 17.6% |
| 4 pCi/L and above | 5 | 14.7% |
What these figures count
These are the 34 tests reported to CDC for Madera 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).
Madera County, Compared
Madera County radon figures, compared
Calculated by Radon41114.7% of its 34 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 4.4 points above the 10.3% pooled from 56 California counties.
Ordered from highest share down, it comes 12th 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%; Madera County sits 21.0 points below it.
Next door, the shares run from 11.0% in Fresno County to 23.0% in Tuolumne County, with Fresno County below Madera County. Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 14.7% share point the same way here.
Half the tests came in under 1.4 pCi/L and half over it; the single highest reached 9.5 pCi/L. The rest split 67.6% under 2 pCi/L and 17.6% from 2 to 4 (California: 76.8% and 12.9%).
CDC's ten-year totals for Madera County went from 32 tests (2005 to 2014) to 34 (2008 to 2017), the share going from 9.4% to 14.7%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Madera County, Geology
The ground under Madera County
PredictedUSGS's geologic map splits Madera County: 63.4% of its land is moderate radon potential and 36.6% low. The map puts 63.4% of Madera County in the area it calls Sierra Nevada and 36.6% in Great Valley. 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 | 63.4% |
| Great Valley | Quaternary alluvial gravel, sand, silt, clay. | Low | 8 | 36.6% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Madera County beside the ground around it
Across California 0.1% of the land is rated high; none of Madera County's is. Of the 5 counties that border it, 3 have more moderate-potential ground, Mariposa County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Madera County, Local resources
Radon testing and mitigation in Madera 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
Madera County, Questions
Questions about radon in Madera County
Are radon levels high in Madera County?
Over the 2008 to 2017 laboratory totals, 14.7% of the radon tests reported to CDC for Madera County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.4 pCi/L. Of 33 California counties with 30 or more tests for the same period, 11 reported a higher share; pooled, the state comes to 10.3%.
Which counties border Madera County?
Madera County borders 5 counties: Mariposa County, Fresno County, Merced County, Tuolumne County and Mono County.
Products
Madera County, Products
Testing a home in Madera County
In Madera County, 14.7% of 34 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 10.3% pooled across California. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Madera County; a long-term test tells the year-round average.
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
MonitorAEGTEST
HOUND-1011S rechargeable radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 12 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Madera County, Bordering counties
Counties bordering Madera County
Calculated by Radon411- Radon levels in Mono CountyEPA zone 2
50.0%at or above 4 pCi/L
Median 4.6 pCi/L · 20 tests · 35.3 points above Madera County
- Radon levels in Tuolumne CountyEPA zone 2
23.0%at or above 4 pCi/L
Median 1.4 pCi/L · 74 tests · 8.3 points above Madera County
- Radon levels in Mariposa CountyEPA zone 2
16.7%at or above 4 pCi/L
Median 1.3 pCi/L · 6 tests · 2.0 points above Madera County
- Radon levels in Fresno CountyEPA zone 2
11.0%at or above 4 pCi/L
Median 1.5 pCi/L · 100 tests · 3.7 points below Madera County
- Radon levels in Merced CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.1 pCi/L · 5 tests · 14.7 points below Madera County
Madera County, Cities and towns
Cities and towns in Madera County
Madera County is growing: the Census Bureau puts it at 167,927 residents on July 1, 2025, up 7.4% from 156,396 in 2020. That works out to 79 people per square mile of land. Its largest town, Madera, has 69,017 residents, 41.1% of the total. Together its 2 incorporated places hold 52.3% of those residents; the other 47.7% live outside any of them. CDC's 34 reported tests for 2008 to 2017 work out to 0.2 per 1,000 residents (2025 estimate), close to California's 0.2.
From Madera to Chowchilla, CDC publishes no figure by town: each reads Madera County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Madera | 69,017 | +3.7% | 41.1% |
| Chowchilla | 18,730 | −0.7% | 11.2% |
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).
Madera County, Homes
Homes in Madera County
Madera County is a place of houses on their own lots: 80% of its 50,368 homes are detached single-family houses, against 57% across California. Much of Madera County is recent building: 30% of its homes have gone up since 2000 and the middle year built is 1988, against 1976 for California. 66% 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 | Madera County | California |
|---|---|---|
| Housing units | 50,368 | 14,532,683 |
| Detached houses | 80% | 57% |
| In buildings of 5 or more | 7% | 24% |
| Mobile homes | 7% | 4% |
| Built before 1960 | 14% | 27% |
| Built since 2000 | 30% | 18% |
| Middle year built | 1988 | 1976 |
| Owner-occupied | 66% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.