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 Callahan County, Texas
EPA puts Callahan 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
Nearest county
10.6%
Tarrant County, 126 miles
- Tarrant
- 10.6%
- Texas
- 10.4%
Share at 4+ pCi/L, 312 tests, 2007 to 2016
Ground above low
None
27.3 pts below Texas
- Callahan
- 0.0%
- Texas
- 27.3%
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 Callahan 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
Callahan County, At a glance
Callahan 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
No CDC test figures here
CDC has published no radon test figures for Callahan County. Tarrant County, 126 miles away, is the nearest county with a figure over the 2007 to 2016 laboratory totals.
Callahan County, Compared
Callahan County radon figures, compared
Calculated by Radon411CDC's county radon counts over the 2007 to 2016 laboratory totals cover 140 Texas counties, and Callahan County is not among them: no year's figure and no ten-year laboratory total names it. Pooled across 140 Texas counties, 10.4% of reported tests reached that level; across every county in the country with a figure, 35.8%.
The nearest counties with a figure are Tarrant County (126 miles away) at 10.6%, McLennan County (138 miles away) at 17.1% and Bell County (141 miles away) at 14.3%. Statewide for the same period, Randall County reported the highest share (71.4%) and Nueces County the lowest (0.0%).
EPA's 1993 map puts Callahan 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.
Callahan County, Geology
The ground under Callahan County
PredictedUSGS's geologic map puts all of Callahan County's mapped land in one class: low radon potential. The map puts 80.1% of Callahan County in the area it calls Central Texas and 19.9% in Central Texas/Gulf Coast Plain. USGS gives both a radon index of 7, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Central Texas | Cretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite. | Low | 7 | 80.1% |
| Central Texas/Gulf Coast Plain | Cretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite. | Low | 7 | 19.9% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Callahan County beside the ground around it
Across Texas 0.5% of the land is rated high; none of Callahan County's is. None of the 6 counties that border it has any moderate-potential ground either.
The map rates the ground, not the air in any home.
Local help
Callahan County, Local resources
Radon testing and mitigation in Callahan County
- Texas Radon GroupTexas Radon Group, run by Texas Tech University, does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Texas.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The Texas Radon Group offers free radon test kits for Texas individuals who qualify.
- Compare kits
- Professionals in Texas7 professionals are listed in Texas.
What Texas's program says
- Licensing of radon professionals
There are no radon certification requirements for the State of Texas at this time, but the National Radon Proficiency Program lists radon testers and mitigators within Texas that have passed a rigorous national certification program.
What it means
Callahan County, Questions
Questions about radon in Callahan County
Are radon levels high in Callahan County?
No CDC testing statistics are published here for Callahan County, Texas yet. Of the 8 nearest counties with a figure, within 165 miles, the share of tests at or above 4 pCi/L runs from 1.0% to 17.1%.
Which counties border Callahan County?
Callahan County borders 6 counties: Shackelford County, Taylor County, Eastland County, Coleman County, Brown County and Jones County.
Products
Callahan County, Products
Testing a home in Callahan County
No CDC figure names Callahan County; the nearest county with one, Tarrant County (126 miles away), reported 10.6% of its tests at or above 4 pCi/L over the 2007 to 2016 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 Callahan 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
Callahan County, Bordering counties
Counties bordering Callahan County
Calculated by Radon411- Radon levels in Taylor CountyEPA zone 3
11.1%at or above 4 pCi/L
Median 0.6 pCi/L · 18 tests
- Radon levels in Shackelford CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.0 pCi/L · 1 test
- Radon levels in Eastland CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.1 pCi/L · 3 tests
- Radon levels in Brown CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.8 pCi/L · 1 test
- Radon levels in Jones CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.7 pCi/L · 1 test
- Radon levels in Coleman CountyEPA zone 3
No CDC figure for 2007 to 2016; its page reads it against its own neighbours.
Callahan County, Cities and towns
Cities and towns in Callahan County
Callahan County is growing: the Census Bureau puts it at 14,491 residents on July 1, 2025, up 5.4% from 13,748 in 2020. That works out to 16 people per square mile of land. Its largest town, Clyde, has 4,024 residents, 27.8% of the total. Together its 4 incorporated places hold 45.3% of those residents; the other 54.7% live outside any of them. CDC publishes no radon test count for Callahan County; across Texas its counts for 2007 to 2016 come to 0.1 tests for every 1,000 residents (2025 estimate).
From Clyde to Putnam, CDC publishes no figure by town: each reads Callahan County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Clyde | 4,024 | +5.3% | 27.8% |
| Baird | 1,532 | +3.5% | 10.6% |
| Cross Plains | 938 | +3.4% | 6.5% |
| Putnam | 70 | +6.1% | 0.5% |
4 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).
Callahan County, Homes
Homes in Callahan County
Callahan County is a place of houses on their own lots: 80% of its 6,523 homes are detached single-family houses, against 65% across Texas. The homes are older than Texas' as a whole: half were built before 1976 (1990 for Texas), and 31% date from before 1960. Owners live in 82% of the occupied homes (Texas: 63%), so for most households a test and a fix are their own to order.
| Homes | Callahan County | Texas |
|---|---|---|
| Housing units | 6,523 | 11,890,808 |
| Detached houses | 80% | 65% |
| In buildings of 5 or more | under 1% | 21% |
| Mobile homes | 18% | 7% |
| Built before 1960 | 31% | 13% |
| Built since 2000 | 24% | 37% |
| Middle year built | 1976 | 1990 |
| Owner-occupied | 82% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.