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Radon Levels in Guilford County, North Carolina

EPA puts Guilford County in Zone 3, its lowest radon zone, and only 13 radon tests from it are on file with CDC (2022). Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    7.9%

    14.7 pts below NC

    Guilford
    7.9%
    NC
    22.6%

    6,870 tests, 2008 to 2017

  • Median result

    0.9pCi/L

    Below action level

    Guilford
    0.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    6,870

    2nd of 75 by tests

    Guilford
    6,870
    Wake
    9,694

    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 NC

    58 of 75

    Lowest quarter

    Guilford
    7.9%
    Transylvania
    47.8%

    By share, of 75 with 30+ tests

Read a result for Guilford County

Starts at Guilford County's median, 0.9 pCi/L

0.9pCi/L

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

EPA’s reading of 0.9 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. Guilford County's median reported result, 2008 to 2017.

Interpret this reading

The data

Guilford County, At a glance

Guilford County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Guilford 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: Low across 91% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Guilford County, 2022

Share of reported tests at or above 4 pCi/L, by year, Guilford County
Share of reported tests at or above 4 pCi/L, by year, Guilford County
YearShare of reported tests at or above 4 pCi/L
20147.6%
20208.3%
20213.4%
202215.4%

2022: 15.4%. Across these years the share ran from 3.4% to 15.4%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 13 tests were reported to CDC for Guilford County over 2022, 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: 2022. Measured data period: 2005 to 2022 (every CDC figure on file).

How to read these figures

Guilford County, Compared

Guilford County radon figures, compared

Calculated by Radon411

Guilford County reports fewer high tests than North Carolina overall. 7.9% of its 6,870 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 14.7 points below the 22.6% pooled from 99 North Carolina counties.

The newest figure, in 2022, counts only 13 tests (15.4% at or above 4 pCi/L), too few to compare, so this reading uses the 6,870-test figure.

Ordered from highest share down, it comes 58th of 75 North Carolina counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Guilford County sits 27.8 points below it.

Next door, the shares run from 3.7% in Alamance County to 28.9% in Forsyth County, with Randolph County and Alamance County below Guilford County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 7.9% share point the same way here.

Half the tests came in under 0.9 pCi/L and half over it; the single highest reached 68.4 pCi/L. The rest split 79.7% under 2 pCi/L and 12.4% from 2 to 4 (North Carolina: 55.6% and 21.8%). Year by year, 2014 opened at 7.6% and 2021 closed at 3.4% (down 4.2 points), with 2020 the high at 8.3%.

The busiest year on file was 2014, with 827 tests reported; the quietest, 2022, had 13.

Share of reported tests at or above 4 pCi/L by year, Guilford County against North Carolina2014 to 2021, years with 30 or more tests: Guilford County 7.6% to 3.4%, the state's pooled share 14.9% in 2021.
Guilford CountyNorth Carolina, pooled
Share of reported tests at or above 4 pCi/L by year, Guilford County against North Carolina: data table
YearTestsGuilford County, at or above 4 pCi/LNorth Carolina, pooled
20148277.6%21.9%
20204328.3%21.1%
20212053.4%14.9%
Guilford County against North Carolina, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Guilford County
Guilford County6,8707.9%0.9 pCi/LThis county
North Carolina, pooled99 counties, pooled73,13922.6%Not pooled+14.7 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+27.8 points
Transylvania Countyhighest in the state3,86247.8%3.7 pCi/L+39.9 points
Nash Countylowest in the state300.0%0.2 pCi/L−7.9 points
Forsyth County, NCborders it6,27328.9%2.3 pCi/L+21.0 points
Rockingham County, NCborders it83527.3%2.1 pCi/L+19.4 points
Davidson County, NCborders it1,26525.5%1.8 pCi/L+17.6 points
Stokes County, NCborders it59221.6%1.8 pCi/L+13.7 points
Randolph County, NCborders it4227.1%0.9 pCi/L−0.8 points
Alamance County, NCborders it5203.7%0.5 pCi/L−4.2 points
Where Guilford County's reported results fell, 2008 to 2017, laboratory, beside North Carolina and the United States
ResultGuilford County testsGuilford County shareNorth Carolina shareU.S. shareAgainst North Carolina
Under 2 pCi/L5,47379.7%55.6%39.6%+24.1 points
2 to 4 pCi/L85312.4%21.8%24.7%−9.4 points
4 pCi/L and above5447.9%22.6%35.7%−14.7 points
Guilford County ranked among the 75 North Carolina counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Wake County53 of 759,6949.6%1.0 pCi/L
Cabarrus County54 of 758808.8%1.0 pCi/L
Mecklenburg County55 of 753,7538.5%0.9 pCi/L
Johnston County56 of 756688.2%0.7 pCi/L
Wayne County57 of 75498.2%0.6 pCi/L
Guilford County58 of 756,8707.9%0.9 pCi/L
Randolph County59 of 754227.1%0.9 pCi/L
Durham County60 of 751,5704.3%0.7 pCi/L
Robeson County61 of 75533.8%0.8 pCi/L
Alamance County62 of 755203.7%0.5 pCi/L
New Hanover County63 of 751173.4%0.1 pCi/L
Guilford County radon tests by year, against North Carolina's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNorth Carolina, pooledChange from the row before
20221315.4%1.0 pCi/L4.0 pCi/L10.7%+12.0 points
20212053.4%0.1 pCi/L7.0 pCi/L14.9%−4.9 points
20204328.3%0.4 pCi/L26.0 pCi/L21.1%+0.7 points
20148277.6%0.1 pCi/L17.7 pCi/L21.9%First on file

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

Guilford County, Geology

The ground under Guilford County

Predicted

Most of the ground under Guilford County is one class on USGS's geologic map: 90.9% of its land is low radon potential, with 9.1% moderate. The map puts 64.2% of Guilford County in the area it calls Carolina Slate Belt and 26.8% in Charlotte Belt, with one smaller area beside them. USGS gives the first a radon index of 6 and the second 8, both in the low band (5 to 8).

USGS's geologic areas under Guilford County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Carolina Slate BeltFelsic metavolcanics, intermediate volcanics, metamudstone, argillite, and epiclastic rocks.Low664.2%
Charlotte BeltIgneous rocks, including granite, gabbro, and diorite.Low826.8%
Milton BeltProterozoic-Cambrian biotite gneiss and felsic mica gneiss.Moderate119.1%

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

Guilford County beside the ground around it

Across North Carolina 1.3% of the land is rated high; none of Guilford County's is. Of the 6 counties that border it, 1 has more high-potential ground, Stokes County the most at 0.1%.

Share of land by USGS radon potential: Guilford County, the 6 counties bordering it and North Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Guilford CountyZone 390.9%9.1%None
Rockingham CountyZone 119.2%80.7%None
Alamance CountyZone 3100%NoneNone
Forsyth CountyZone 223.7%76.3%None
Randolph CountyZone 3100%NoneNone
Stokes CountyZone 210.3%89.7%0.1%
Davidson CountyZone 3100%NoneNone
North Carolina100 counties, pooled by land areaVaries64.8%33.0%1.3%

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

Local help

Guilford County, Local resources

Radon testing and mitigation in Guilford County

What North Carolina's program says
Licensing of radon professionals
The North Carolina Radon Program is presently developing a Radon Proficiency Program as directed by Session Law 2023-91 House Bill 782 .

What it means

Guilford County, Questions

Questions about radon in Guilford County

Are radon levels high in Guilford County?

In 2022, 15.4% of the radon tests reported to CDC for Guilford County, North Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.0 pCi/L. Of 75 North Carolina counties with 30 or more tests for the same period, 57 reported a higher share; pooled, the state comes to 22.6%.

Which counties border Guilford County?

Guilford County borders 6 counties: Rockingham County, Alamance County, Forsyth County, Randolph County, Stokes County and Davidson County.

Products

Guilford County, Products

Testing a home in Guilford County

In Guilford County, 7.9% of 6,870 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 22.6% pooled across North Carolina. 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 Guilford County.

Test kits and monitors3

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Best radon monitors for Guilford County homes, compared

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Guilford County, Bordering counties

Counties bordering Guilford County

Calculated by Radon411

Guilford County, Cities and towns

Cities and towns in Guilford County

The Census Bureau estimates 562,234 residents in Guilford County for July 1, 2025, 23,508 more than in 2020 (+4.4%). That works out to 870 people per square mile of land. Greensboro alone is home to 308,667 of them, 54.9% of the total. Testing is reported here more often than across the state: CDC's 6,870 reported tests for 2008 to 2017 come to 12.2 for every 1,000 residents (2025 estimate), against 6.5 for North Carolina.

From Greensboro to Whitsett, CDC publishes no figure by town: each reads Guilford County's.

The 12 largest cities and towns in Guilford County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Greensboro308,667+4.3%54.9%
High Pointextends beyond Guilford County120,571+5.1%Counted whole
Burlingtonextends beyond Guilford County61,496+6.8%Counted whole
Kernersvilleextends beyond Guilford County29,128+9.6%Counted whole
Archdaleextends beyond Guilford County12,254+2.9%Counted whole
Summerfield11,327+3.4%2.0%
Gibsonvilleextends beyond Guilford County9,876+7.9%Counted whole
Oak Ridge7,896+3.4%1.4%
Stokesdale6,133+3.6%1.1%
Pleasant Garden5,165+3.4%0.9%
Jamestown3,803+3.1%0.7%
Sedalia691+3.0%0.1%
  • Whitsett

13 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 Guilford County is counted whole, so it has no share.

Guilford County, Homes

Homes in Guilford County

Of Guilford County's 235,833 homes, 63% are detached houses, against 65% across North Carolina; 22% are in buildings of five or more homes. Half of its homes were built before 1986, close to North Carolina's 1990: 18% date from before 1960 and 28% from 2000 or later. 60% of occupied homes are lived in by their owner (North Carolina: 66%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Guilford County, North Carolina, 2019 to 2023
HomesGuilford CountyNorth Carolina
Housing units235,8334,815,195
Detached houses63%65%
In buildings of 5 or more22%14%
Mobile homes3%11%
Built before 196018%14%
Built since 200028%33%
Middle year built19861990
Owner-occupied60%66%

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