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Radon Levels in Mason County, Texas

EPA puts Mason County in Zone 2, its middle radon zone. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Nearest county

    9.3%

    Travis County, 90 miles

    Travis
    9.3%
    Texas
    10.4%

    Share at 4+ pCi/L, 408 tests, 2007 to 2016

  • Ground above low

    85.7%

    58.4 pts above Texas

    Mason
    85.7%
    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 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

Read a result for Mason County

Starts at EPA's action level

4.0pCi/L

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

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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.

Interpret this readingWhat a fix costs

The data

Mason County, At a glance

Mason County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Mason County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 86% 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 Mason County. Travis County, 90 miles away, is the nearest county with a figure over the 2007 to 2016 laboratory totals.

How to read these figures

Mason County, Compared

Mason County radon figures, compared

Calculated by Radon411

CDC's county radon counts over the 2007 to 2016 laboratory totals cover 140 Texas counties, and Mason 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 Travis County (90 miles away) at 9.3%, Williamson County (97 miles away) at 2.0% and Bexar County (97 miles away) at 6.6%. 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 Mason County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 86% of the county's land moderate radon potential.

Texas, the United States and the counties around Mason County, 2007 to 2016, laboratory
AreaTestsAt or above 4 pCi/LMedian
Texas, pooled140 counties, pooled4,54810.4%Not pooled
United States, pooled2,666 counties, pooled1,939,02535.8%Not pooled
Randall Countyhighest in the state8471.4%6.2 pCi/L
Nueces Countylowest in the state450.0%0.6 pCi/L
Gillespie County, TXborders it1020.0%0.8 pCi/L
Kimble County, TXborders it10.0%2.1 pCi/L
Llano County, TXborders it60.0%1.5 pCi/L
The nearest Texas counties to Mason County with 30 or more tests, 2007 to 2016, laboratory
CountyDistanceTestsAt or above 4 pCi/LMedian
Travis County90 mi4089.3%0.8 pCi/L
Williamson County97 mi982.0%0.7 pCi/L
Bexar County97 mi1976.6%0.6 pCi/L
Bell County106 mi3514.3%1.1 pCi/L
McLennan County133 mi4117.1%1.0 pCi/L
Brazos County174 mi490.0%0.2 pCi/L
Tarrant County182 mi31210.6%0.9 pCi/L
Midland County184 mi1001.0%0.7 pCi/L

Pooled shares: Radon411's sum of CDC's county counts for one period.

Mason County, Geology

The ground under Mason County

Predicted

Most of the ground under Mason County is one class on USGS's geologic map: 85.7% of its land is moderate radon potential, with 14.3% low. The map puts 85.7% of Mason County in the area it calls Llano Uplift and 14.3% in Southern High Plains and Plateaus. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 7, in the low band (5 to 8).

USGS's geologic areas under Mason County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Llano UpliftPrecambrian metamorphic and undifferentiated igneous rocks.Moderate1085.7%
Southern High Plains and PlateausPaleozoic and Mesozoic sandstone, limestone, shale.Low714.3%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Mason County beside the ground around it

Across Texas 0.5% of the land is rated high; none of Mason County's is. Of the 6 counties that border it, 1 has more moderate-potential ground, Llano County the most at 100%.

Share of land by USGS radon potential: Mason County, the 6 counties bordering it and Texas
AreaEPA zoneLow potentialModerate potentialHigh potential
Mason CountyZone 214.3%85.7%None
McCulloch CountyZone 378.5%21.5%None
Llano CountyZone 2None100%None
Gillespie CountyZone 386.8%13.2%None
Menard CountyZone 3100%NoneNone
San Saba CountyZone 352.1%47.9%None
Kimble CountyZone 398.3%1.7%None
Texas254 counties, pooled by land areaVaries72.4%26.8%0.5%

The map rates the ground, not the air in any home.

Local help

Mason County, Local resources

Radon testing and mitigation in Mason County

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

Mason County, Questions

Questions about radon in Mason County

Are radon levels high in Mason County?

No CDC testing statistics are published here for Mason County, Texas yet. Of the 8 nearest counties with a figure, within 184 miles, the share of tests at or above 4 pCi/L runs from 0.0% to 17.1%.

Which counties border Mason County?

Mason County borders 6 counties: McCulloch County, Llano County, Gillespie County, Menard County, San Saba County and Kimble County.

Products

Mason County, Products

Testing a home in Mason County

No CDC figure names Mason County; the nearest county with one, Travis County (90 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. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Mason County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Mason County homes, compared

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Mason County, Bordering counties

Counties bordering Mason County

Calculated by Radon411

Mason County, Cities and towns

Cities and towns in Mason County

The Census Bureau estimates 3,990 residents in Mason County for July 1, 2025, 20 more than in 2020 (+0.5%). Spread over its land, that is 4.3 people to the square mile. Mason, its one incorporated place, has 2,171 residents, 54.4% of the total. CDC publishes no radon test count for Mason County; across Texas its counts for 2007 to 2016 come to 0.1 tests for every 1,000 residents (2025 estimate).

Mason is the one incorporated place here; CDC publishes no figure by town, so it reads Mason County's.

Mason, Mason County: residents on July 1, 2025
PlaceResidentsSince 2020Share of residents
Mason2,171+1.6%54.4%

One incorporated place, 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).

Mason County, Homes

Homes in Mason County

Mason County is a place of houses on their own lots: 85% of its 2,411 homes are detached single-family houses, against 65% across Texas. The homes are older than Texas' as a whole: half were built before 1972 (1990 for Texas), and 36% date from before 1960. Owners live in 76% of the occupied homes (Texas: 63%), so for most households a test and a fix are their own to order.

Homes in Mason County, Texas, 2019 to 2023
HomesMason CountyTexas
Housing units2,41111,890,808
Detached houses85%65%
In buildings of 5 or moreunder 1%21%
Mobile homes11%7%
Built before 196036%13%
Built since 200020%37%
Middle year built19721990
Owner-occupied76%63%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.