Short-term kitKidde
442020 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 3 days
Locations and reports
Radon Levels in Comal County, Texas
EPA puts Comal County in Zone 3, its lowest radon zone, and only 22 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
6.6%
Bexar County
- Bexar
- 6.6%
1 of 5 neighbours have 30+ tests, 2007 to 2016
Nearest county
6.6%
Bexar County, 29 miles
- Bexar
- 6.6%
- Texas
- 10.4%
Share at 4+ pCi/L, 197 tests, 2007 to 2016
Ground above low
None
27.3 pts below Texas
- Comal
- 0.0%
- Texas
- 27.3%
Share of land USGS rates moderate or high potential
Tests reported
22
Too few for a share
- Comal
- 22
- 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 Comal 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
Comal County, At a glance
Comal 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 Comal County, 2008 to 2017, laboratory
CDC holds 22 reported tests for Comal County over the 2008 to 2017 laboratory totals, with a median of 0.9 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Comal County beside the counties around it is how this page reads it.
What these figures count
Only 22 tests were reported to CDC for Comal 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).
Comal County, Compared
Comal County radon figures, compared
Calculated by Radon411CDC's largest figure for Comal County rests on 22 tests over the 2008 to 2017 laboratory totals, 1 of them at or above 4 pCi/L, so each test moves its share by 4.5 points and no rank or comparison is drawn from it. Results reached as high as 10.2 pCi/L, with a middle value of 0.9 pCi/L.
Bexar County, the one bordering county with a figure over the 2007 to 2016 laboratory totals, reported 6.6% of its tests at or above 4 pCi/L. Farther out, Travis County (47 miles away) at 9.3%, Williamson County (71 miles away) at 2.0% and Bell County (97 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 Comal 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.
Comal County, Geology
The ground under Comal County
PredictedUSGS's geologic map puts all of Comal County's mapped land in one class: low radon potential. The map puts 65.7% of Comal County in the area it calls Southern High Plains and Plateaus and 34.3% in East Texas Province. USGS gives the first a radon index of 7 and the second 6, both in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Southern High Plains and Plateaus | Paleozoic and Mesozoic sandstone, limestone, shale. | Low | 7 | 65.7% |
| East Texas Province | Cretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite. | Low | 6 | 34.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Comal County beside the ground around it
Across Texas 0.5% of the land is rated high; none of Comal County's is. Of the 5 counties that border it, 2 have more moderate-potential ground, Blanco County the most at 35.3%.
The map rates the ground, not the air in any home.
Local help
Comal County, Local resources
Radon testing and mitigation in Comal 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
Comal County, Questions
Questions about radon in Comal County
Are radon levels high in Comal County?
Over the 2008 to 2017 laboratory totals, 4.5% of the radon tests reported to CDC for Comal County, Texas were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Bexar County, the one bordering county with a figure over the 2007 to 2016 laboratory totals, reported 6.6% of its tests at or above 4 pCi/L.
Which counties border Comal County?
Comal County borders 5 counties: Guadalupe County, Kendall County, Hays County, Blanco County and Bexar County.
Products
Comal County, Products
Testing a home in Comal County
No CDC figure names Comal County; the nearest county with one, Bexar County (29 miles away), reported 6.6% 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 Comal 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
MonitorSafetySiren
Pro4 plug-in radon detector with a display and alarm
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
First reading: Within 48 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Comal County, Bordering counties
Counties bordering Comal County
Calculated by Radon411- Radon levels in Kendall CountyEPA zone 3
71.4%at or above 4 pCi/L
Median 5.7 pCi/L · 7 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 Bexar CountyEPA zone 3
6.6%at or above 4 pCi/L
Median 0.6 pCi/L · 197 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 Blanco CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.2 pCi/L · 2 tests
Comal County, Cities and towns
Cities and towns in Comal County
Comal County is growing: the Census Bureau puts it at 209,166 residents on July 1, 2025, up 27.8% from 163,608 in 2020. That works out to 374 people per square mile of land. San Antonio, the largest place on its list (1,548,422 residents in all), extends beyond Comal County, so no share of the total is worked out for it. CDC's 22 reported tests for 2008 to 2017 work out to 0.1 per 1,000 residents (2025 estimate), close to Texas' 0.1.
From San Antonio to Spring Branch, CDC publishes no figure by town: each reads Comal County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| San Antonioextends beyond Comal County | 1,548,422 | +7.7% | Counted whole |
| New Braunfelsextends beyond Comal County | 122,492 | +33.7% | Counted whole |
| Schertzextends beyond Comal County | 45,978 | +8.8% | Counted whole |
| Fair Oaks Ranchextends beyond Comal County | 12,025 | +21.0% | Counted whole |
| Selmaextends beyond Comal County | 11,955 | +4.6% | Counted whole |
| Bulverde | 7,337 | +28.5% | 3.5% |
| Garden Ridge | 4,371 | +4.2% | 2.1% |
| Spring Branch | 267 | +23.0% | 0.1% |
Places in Comal County with a city page: 1 of 1
8 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 Comal County is counted whole, so it has no share.
Comal County, Homes
Homes in Comal County
Of Comal County's 74,484 homes, 74% are detached houses, against 65% across Texas; 12% are in buildings of five or more homes. Much of Comal County is recent building: 57% of its homes have gone up since 2000 and the middle year built is 2003, against 1990 for Texas. Owners live in 77% of the occupied homes (Texas: 63%), so for most households a test and a fix are their own to order.
| Homes | Comal County | Texas |
|---|---|---|
| Housing units | 74,484 | 11,890,808 |
| Detached houses | 74% | 65% |
| In buildings of 5 or more | 12% | 21% |
| Mobile homes | 9% | 7% |
| Built before 1960 | 7% | 13% |
| Built since 2000 | 57% | 37% |
| Middle year built | 2003 | 1990 |
| Owner-occupied | 77% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.