Short-term kit
Radon Short Term Test Kit short-term charcoal radon test kit, lab fee included
- Lab fee included
Method: Charcoal
In home: 2 to 7 days
Locations and reports
Radon Levels in Blanco County, Texas
EPA puts Blanco 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 7 neighbours have 30+ tests, 2007 to 2016
Nearest county
9.3%
Travis County, 37 miles
- Travis
- 9.3%
- Texas
- 10.4%
Share at 4+ pCi/L, 408 tests, 2007 to 2016
Ground above low
35.3%
8.0 pts above Texas
- Blanco
- 35.3%
- Texas
- 27.3%
Share of land USGS rates moderate or high potential
Tests reported
2
Too few for a share
- Blanco
- 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 Blanco 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
Blanco County, At a glance
Blanco County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 65% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Blanco County, 2008 to 2017, laboratory
CDC holds 2 reported tests for Blanco County over the 2008 to 2017 laboratory totals, with a median of 0.2 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Blanco County beside the counties around it is how this page reads it.
What these figures count
Only 2 tests were reported to CDC for Blanco 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).
Blanco County, Compared
Blanco County radon figures, compared
Calculated by Radon411CDC's largest figure for Blanco 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 0.2 pCi/L, with a middle value of 0.2 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 (54 miles away) at 2.0%, Bexar County (57 miles away) at 6.6% and Bell County (76 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 Blanco County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 65% of the county's land low radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Blanco County, Geology
The ground under Blanco County
PredictedUSGS's geologic map splits Blanco County: 64.7% of its land is low radon potential and 35.3% moderate. The map puts 64.7% of Blanco County in the area it calls Southern High Plains and Plateaus and 35.3% in Llano Uplift. USGS gives the first a radon index of 7, in the low band (5 to 8), and the second 10, in the moderate band (9 to 11).
| 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 | 64.7% |
| Llano Uplift | Precambrian metamorphic and undifferentiated igneous rocks. | Moderate | 10 | 35.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Blanco County beside the ground around it
Across Texas 0.5% of the land is rated high; none of Blanco County's is. Of the 7 counties that border it, 1 has more moderate-potential ground, Llano County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Blanco County, Local resources
Radon testing and mitigation in Blanco 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
Blanco County, Questions
Questions about radon in Blanco County
Are radon levels high in Blanco County?
Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Blanco County, Texas were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.2 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 Blanco County?
Blanco County borders 7 counties: Hays County, Comal County, Kendall County, Gillespie County, Llano County, Burnet County and Travis County.
Products
Blanco County, Products
Testing a home in Blanco County
No CDC figure names Blanco County; the nearest county with one, Travis County (37 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 Blanco 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
Monitor
Corentium Home battery digital radon detector
- C-NRPP 2024/25: Approved
- Battery
- Screen
Method: Alpha spectrometry
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Blanco County, Bordering counties
Counties bordering Blanco 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 Burnet CountyEPA zone 3
71.4%at or above 4 pCi/L
Median 27.4 pCi/L · 7 tests
- Radon levels in Gillespie CountyEPA zone 3
20.0%at or above 4 pCi/L
Median 0.8 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 Comal CountyEPA zone 3
4.5%at or above 4 pCi/L
Median 0.9 pCi/L · 22 tests
- Radon levels in Llano CountyEPA zone 2
0.0%at or above 4 pCi/L
Median 1.5 pCi/L · 6 tests
Blanco County, Cities and towns
Cities and towns in Blanco County
Blanco County is growing: the Census Bureau puts it at 13,581 residents on July 1, 2025, up 18.6% from 11,451 in 2020. That works out to 19 people per square mile of land. No town dominates: Johnson City, the largest, has 2,127 residents, 15.7% of the total. Together its 3 incorporated places hold 32.0% of those residents; the other 68.0% live outside any of them. CDC's 2 reported tests for 2008 to 2017 work out to 0.1 per 1,000 residents (2025 estimate), close to Texas' 0.1.
From Johnson City to Round Mountain, CDC publishes no figure by town: each reads Blanco County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Johnson City | 2,127 | +20.8% | 15.7% |
| Blanco | 2,108 | +24.7% | 15.5% |
| Round Mountain | 109 | +18.5% | 0.8% |
3 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).
Blanco County, Homes
Homes in Blanco County
Blanco County is a place of houses on their own lots: 81% of its 6,099 homes are detached single-family houses, against 65% across Texas. Half of its homes were built before 1997, close to Texas' 1990: 19% date from before 1960 and 44% from 2000 or later. 74% 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 | Blanco County | Texas |
|---|---|---|
| Housing units | 6,099 | 11,890,808 |
| Detached houses | 81% | 65% |
| In buildings of 5 or more | 4% | 21% |
| Mobile homes | 10% | 7% |
| Built before 1960 | 19% | 13% |
| Built since 2000 | 44% | 37% |
| Middle year built | 1997 | 1990 |
| Owner-occupied | 74% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.