Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Caldwell County, Texas
EPA puts Caldwell 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
9.3%
Travis County
- Travis
- 9.3%
1 of 6 neighbours have 30+ tests, 2007 to 2016
Nearest county
9.3%
Travis County, 36 miles
- Travis
- 9.3%
- Texas
- 10.4%
Share at 4+ pCi/L, 408 tests, 2007 to 2016
Ground above low
None
27.3 pts below Texas
- Caldwell
- 0.0%
- Texas
- 27.3%
Share of land USGS rates moderate or high potential
Tests reported
2
Too few for a share
- Caldwell
- 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 Caldwell 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
Caldwell County, At a glance
Caldwell 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 Caldwell County, 2008 to 2017, laboratory
CDC holds 2 reported tests for Caldwell County over the 2008 to 2017 laboratory totals, with a median of 1.1 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Caldwell County beside the counties around it is how this page reads it.
What these figures count
Only 2 tests were reported to CDC for Caldwell 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).
Caldwell County, Compared
Caldwell County radon figures, compared
Calculated by Radon411CDC's largest figure for Caldwell 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 1.4 pCi/L, with a middle value of 1.1 pCi/L.
Travis County, the one bordering county with a figure over the 2007 to 2016 laboratory totals, reported 9.3% of its tests at or above 4 pCi/L. Farther out, Williamson County (56 miles away) at 2.0%, Bexar County (60 miles away) at 6.6% and Bell County (83 miles away) at 14.3% have figures too. Pooled across 140 Texas counties, 10.4% of reported tests reached that level; across every county in the country with a figure, 35.8%.
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 Caldwell 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.
Caldwell County, Geology
The ground under Caldwell County
PredictedUSGS's geologic map puts all of Caldwell County's mapped land in one class: low radon potential. All of it lies in the area the map calls East Texas Province, to which USGS gives a radon index of 6, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| East Texas Province | Cretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite. | Low | 6 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Caldwell County beside the ground around it
Across Texas 0.5% of the land is rated high; none of Caldwell County's is. Of the 6 counties that border it, 2 have more moderate-potential ground, Travis County the most at 13.5%.
The map rates the ground, not the air in any home.
Local help
Caldwell County, Local resources
Radon testing and mitigation in Caldwell 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
Caldwell County, Questions
Questions about radon in Caldwell County
Are radon levels high in Caldwell County?
Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Caldwell County, Texas were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.1 pCi/L. Travis County, the one bordering county with a figure over the 2007 to 2016 laboratory totals, reported 9.3% of its tests at or above 4 pCi/L.
Which counties border Caldwell County?
Caldwell County borders 6 counties: Guadalupe County, Bastrop County, Gonzales County, Travis County, Hays County and Fayette County.
Products
Caldwell County, Products
Testing a home in Caldwell County
No CDC figure names Caldwell County; the nearest county with one, Travis County (36 miles away), reported 9.3% 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 Caldwell 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
MonitorAEGTEST
HOUND-3786 rechargeable radon monitor with a 3.5-inch color screen
- C-NRPP 2024/25: Not included
- Battery
- 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
Caldwell County, Bordering counties
Counties bordering Caldwell County
Calculated by Radon411- Radon levels in Bastrop CountyEPA zone 3
80.0%at or above 4 pCi/L
Median 11.8 pCi/L · 10 tests
- Radon levels in Hays CountyEPA zone 3
14.8%at or above 4 pCi/L
Median 0.6 pCi/L · 27 tests
- Radon levels in Travis CountyEPA zone 3
9.3%at or above 4 pCi/L
Median 0.8 pCi/L · 408 tests
- Radon levels in Guadalupe CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.6 pCi/L · 3 tests
- Radon levels in Gonzales CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.1 pCi/L · 6 tests
- Radon levels in Fayette CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.1 pCi/L · 6 tests
Caldwell County, Cities and towns
Cities and towns in Caldwell County
Caldwell County is growing: the Census Bureau puts it at 55,150 residents on July 1, 2025, up 20.0% from 45,945 in 2020. That works out to 101 people per square mile of land. San Marcos, the largest place on its list (77,830 residents in all), extends beyond Caldwell County, so no share of the total is worked out for it. Reported testing is thin here: 2 tests over 2008 to 2017, or under 0.1 for every 1,000 residents (2025 estimate), where Texas as a whole comes to 0.1.
From San Marcos to Mustang Ridge, CDC publishes no figure by town: each reads Caldwell County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| San Marcosextends beyond Caldwell County | 77,830 | +14.1% | Counted whole |
| Lockhart | 18,159 | +26.3% | 32.9% |
| Lulingextends beyond Caldwell County | 5,920 | +5.7% | Counted whole |
| Uhlandextends beyond Caldwell County | 1,958 | +23.3% | Counted whole |
| Martindale | 1,298 | +4.4% | 2.4% |
| Niederwaldextends beyond Caldwell County | 1,168 | +73.3% | Counted whole |
| Mustang Ridgeextends beyond Caldwell County | 1,025 | +7.0% | Counted whole |
7 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). A place that extends beyond Caldwell County is counted whole, so it has no share.
Caldwell County, Homes
Homes in Caldwell County
Of Caldwell County's 17,013 homes, 60% are detached houses, against 65% across Texas; 27% are mobile homes. Half of its homes were built before 1988, close to Texas' 1990: 18% date from before 1960 and 33% from 2000 or later. 73% of occupied homes are lived in by their owner (Texas: 63%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Caldwell County | Texas |
|---|---|---|
| Housing units | 17,013 | 11,890,808 |
| Detached houses | 60% | 65% |
| In buildings of 5 or more | 4% | 21% |
| Mobile homes | 27% | 7% |
| Built before 1960 | 18% | 13% |
| Built since 2000 | 33% | 37% |
| Middle year built | 1988 | 1990 |
| Owner-occupied | 73% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.