Skip to content
RADON411

Locations and reports

Radon Levels in Collin County, Texas

EPA puts Collin County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 7.6% of 289 (2008 to 2017, laboratory totals) reached 4 pCi/L. 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

  • Share at 4+ pCi/L

    7.6%

    2.6 pts below TX

    Collin
    7.6%
    Texas
    10.2%

    289 tests, 2008 to 2017

  • Median result

    1.0pCi/L

    Below action level

    Collin
    1.0 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    289

    4th of 22 by tests

    Collin
    289
    Harris
    733

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 3

    Lower potential

    1. 1
    2. 2
    3. Zone 3

    1 highest, 3 lowest

    EPA predicts under 2 pCi/L indoors

  • Rank in Texas

    9 of 22

    Middle half

    Collin
    7.6%
    Randall
    69.0%

    By share, of 22 with 30+ tests

Read a result for Collin County

Starts at Collin County's median, 1.0 pCi/L

1.0pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 1.0 pCi/L

Below 2 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 below 2 pCi/L, the level at which EPA says a fix should be considered. Collin County's median reported result, 2008 to 2017.

Interpret this reading

The data

Collin County, At a glance

Collin County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Collin County as a whole is an average indoor of less than 2 pCi/L (less than 75 Bq/m³). A low zone clears no address in it: homes above EPA's turn up in all three zones.

USGS geologic potential: Moderate across 59% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Collin County, 2008 to 2017, laboratory

Reported results by concentration band, Collin County, 2008 to 2017, laboratory
Under 2 pCi/L: 81%2 to 4 pCi/L: 12%4 pCi/L and above: 7%

Of 289 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Collin County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L23380.6%
2 to 4 pCi/L3411.8%
4 pCi/L and above227.6%
What these figures count

These are the 289 tests reported to CDC for Collin County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Collin County, Compared

Collin County radon figures, compared

Calculated by Radon411

Collin County reports fewer high tests than Texas overall. 7.6% of its 289 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 2.6 points below the 10.2% pooled from 138 Texas counties.

Ordered from highest share down, it comes 9th of 22 Texas counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Collin County sits 28.1 points below it.

Next door, the shares run from 6.8% in Denton County to 8.4% in Dallas County, with Denton County below Collin County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 7.6% share point the same way here.

Half the tests came in under 1.0 pCi/L and half over it; the single highest reached 52.0 pCi/L. The rest split 80.6% under 2 pCi/L and 11.8% from 2 to 4 (Texas: 80.3% and 9.6%).

CDC's ten-year totals for Collin County went from 188 tests (2005 to 2014) to 289 (2008 to 2017), the share going from 7.4% to 7.6%.

Collin County against Texas, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Collin County
Collin County2897.6%1.0 pCi/LThis county
Texas, pooled138 counties, pooled4,61510.2%Not pooled+2.6 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+28.1 points
Randall Countyhighest in the state8769.0%6.1 pCi/L+61.4 points
Nueces Countylowest in the state430.0%0.6 pCi/L−7.6 points
Hunt County, TXborders it425.0%2.0 pCi/L+17.4 points
Rockwall County, TXborders it1618.8%1.2 pCi/L+11.2 points
Dallas County, TXborders it7288.4%0.9 pCi/L+0.8 points
Denton County, TXborders it1926.8%0.9 pCi/L−0.8 points
Grayson County, TXborders it205.0%1.1 pCi/L−2.6 points
Fannin County, TXborders it10.0%0.9 pCi/L−7.6 points
Where Collin County's reported results fell, 2008 to 2017, laboratory, beside Texas and the United States
ResultCollin County testsCollin County shareTexas shareU.S. shareAgainst Texas
Under 2 pCi/L23380.6%80.3%39.6%+0.3 points
2 to 4 pCi/L3411.8%9.6%24.7%+2.2 points
4 pCi/L and above227.6%10.2%35.7%−2.6 points
Collin County ranked among the 22 Texas counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Potter County4 of 227423.0%1.4 pCi/L
Bell County5 of 223016.7%1.3 pCi/L
Tarrant County6 of 2228413.0%0.9 pCi/L
Travis County7 of 224269.2%0.9 pCi/L
Dallas County8 of 227288.4%0.9 pCi/L
Collin County9 of 222897.6%1.0 pCi/L
Denton County10 of 221926.8%0.9 pCi/L
Bexar County11 of 222016.5%0.6 pCi/L
Brazoria County12 of 22326.3%0.3 pCi/L
Smith County13 of 22525.8%0.8 pCi/L
Montgomery County14 of 221883.2%0.8 pCi/L
Collin County ten-year laboratory totals, against Texas' pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestTexas, pooledChange from the row before
2008 to 20172897.6%1.0 pCi/L52.0 pCi/L10.2%−0.1 points
2007 to 20162847.7%1.0 pCi/L52.0 pCi/L10.4%+0.5 points
2006 to 20152637.2%0.9 pCi/L52.0 pCi/L11.0%−0.2 points
2005 to 20141887.4%0.8 pCi/L52.0 pCi/L10.6%First on file

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

Collin County, Geology

The ground under Collin County

Predicted

USGS's geologic map splits Collin County: 59.3% of its land is moderate radon potential and 40.7% low. The map puts 59.3% of Collin County in the area it calls Cretaceous Gulfian series and 40.7% in East Texas Province. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 6, in the low band (5 to 8).

USGS's geologic areas under Collin County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Cretaceous Gulfian seriesCretaceous sandstone, shale, limestone, siltstone.Moderate1059.3%
East Texas ProvinceCretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite.Low640.7%

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

Collin County beside the ground around it

Across Texas 0.5% of the land is rated high; none of Collin County's is. Of the 6 counties that border it, 3 have more moderate-potential ground, Grayson County the most at 85.4%.

Share of land by USGS radon potential: Collin County, the 6 counties bordering it and Texas
AreaEPA zoneLow potentialModerate potentialHigh potential
Collin CountyZone 340.7%59.3%None
Rockwall CountyZone 3100%NoneNone
Grayson CountyZone 314.6%85.4%None
Hunt CountyZone 3100%NoneNone
Denton CountyZone 349.0%51.0%None
Dallas CountyZone 335.2%64.8%None
Fannin CountyZone 317.5%82.5%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

Collin County, Local resources

Radon testing and mitigation in Collin County

Listed radon professionals by town: Dallas, Carrollton, Richardson

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

Collin County, Questions

Questions about radon in Collin County

Are radon levels high in Collin County?

Over the 2008 to 2017 laboratory totals, 7.6% of the radon tests reported to CDC for Collin County, Texas were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.0 pCi/L. Of 22 Texas counties with 30 or more tests for the same period, 8 reported a higher share; pooled, the state comes to 10.2%.

Which counties border Collin County?

Collin County borders 6 counties: Rockwall County, Grayson County, Hunt County, Denton County, Dallas County and Fannin County.

Products

Collin County, Products

Testing a home in Collin County

In Collin County, 7.6% of 289 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 10.2% pooled across Texas. 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 Collin County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Collin County homes, compared

Explore

Collin County, Bordering counties

Counties bordering Collin County

Calculated by Radon411

Collin County, Cities and towns

Cities and towns in Collin County

Collin County is growing: the Census Bureau puts it at 1,297,179 residents on July 1, 2025, up 20.6% from 1,075,512 in 2020. Packed into its land, that is 1,542 people per square mile. Dallas, the largest place on its list (1,329,491 residents in all), extends beyond Collin County, so no share of the total is worked out for it. Testing is reported here more often than across the state: CDC's 289 reported tests for 2008 to 2017 come to 0.2 for every 1,000 residents (2025 estimate), against 0.1 for Texas.

From Dallas to Hebron, CDC publishes no figure by town: each reads Collin County's.

The 12 largest cities and towns in Collin County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Dallasextends beyond Collin County1,329,491+2.0%Counted whole
Planoextends beyond Collin County293,028+2.3%Counted whole
Garlandextends beyond Collin County249,625+1.3%Counted whole
Friscoextends beyond Collin County236,955+16.9%Counted whole
McKinney236,001+19.5%18.2%
Carrolltonextends beyond Collin County134,562+0.7%Counted whole
Richardsonextends beyond Collin County118,542−0.7%Counted whole
Allen113,447+7.5%8.7%
Celinaextends beyond Collin County64,427+257.3%Counted whole
Wylieextends beyond Collin County63,842+10.3%Counted whole
Prosperextends beyond Collin County45,605+47.9%Counted whole
Princeton43,524+148.7%3.4%
  • Anna
  • Sachse (part)
  • Melissa
  • Royse City (part)
  • Murphy
  • Lavon
  • Fairview
  • Josephine (part)
  • Lucas
  • Van Alstyne (part)
  • Parker
  • Farmersville
  • Lowry Crossing
  • Nevada
  • Blue Ridge
  • Weston
  • St. Paul
  • Trenton (part)
  • New Hope
  • Hebron (part)

32 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Collin County is counted whole, so it has no share.

Collin County, Homes

Homes in Collin County

Of Collin County's 421,938 homes, 68% are detached houses, against 65% across Texas; 25% are in buildings of five or more homes. Much of Collin County is recent building: 55% of its homes have gone up since 2000 and the middle year built is 2002, against 1990 for Texas. 64% 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 in Collin County, Texas, 2019 to 2023
HomesCollin CountyTexas
Housing units421,93811,890,808
Detached houses68%65%
In buildings of 5 or more25%21%
Mobile homes2%7%
Built before 19602%13%
Built since 200055%37%
Middle year built20021990
Owner-occupied64%63%

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