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Radon Levels in Madison County, North Carolina

EPA puts Madison County in Zone 2, its middle radon zone, and only 5 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

    14.8%

    8.4 pts below NC

    Madison
    14.8%
    NC
    23.2%

    256 tests, 2007 to 2016

  • Median result

    1.2pCi/L

    Below action level

    Madison
    1.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2007 to 2016

  • Tests reported

    256

    44th of 73 by tests

    Madison
    256
    Wake
    9,664

    Reported to CDC before any fix, 2007 to 2016

  • 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

  • Rank in NC

    47 of 73

    Middle half

    Madison
    14.8%
    Transylvania
    48.1%

    By share, of 73 with 30+ tests

Read a result for Madison County

Starts at Madison County's median, 1.2 pCi/L

1.2pCi/L

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

EPA’s reading of 1.2 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. Madison County's median reported result, 2007 to 2016.

Interpret this reading

The data

Madison County, At a glance

Madison County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Madison 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 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Madison County, 2022

Share of reported tests at or above 4 pCi/L, by year, Madison County
Share of reported tests at or above 4 pCi/L, by year, Madison County
YearShare of reported tests at or above 4 pCi/L
201440.0%
202020.9%
20217.4%
20220.0%

2022: 0.0%. Across these years the share ran from 0.0% to 40.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 5 tests were reported to CDC for Madison 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

Madison County, Compared

Madison County radon figures, compared

Calculated by Radon411

Madison County reports fewer high tests than North Carolina overall. 14.8% of its 256 tests over the 2007 to 2016 laboratory totals were at or above 4 pCi/L. That is 8.4 points below the 23.2% pooled from 99 North Carolina counties.

The newest figure, in 2022, counts only 5 tests (0.0% at or above 4 pCi/L), too few to compare, so this reading uses the 256-test figure.

Ordered from highest share down, it comes 47th of 73 North Carolina counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.8%; Madison County sits 21.0 points below it.

Next door, the shares run from 29.4% in Yancey County to 50.0% in Cocke County, TN. Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 14.8% share point the same way here.

Half the tests came in under 1.2 pCi/L and half over it; the single highest reached 43.1 pCi/L. The rest split 66.0% under 2 pCi/L and 19.1% from 2 to 4 (North Carolina: 55.2% and 21.6%).

The busiest year on file was 2020, with 86 tests reported; the quietest, 2022, had 5.

Madison County against North Carolina, the United States and nearby counties, 2007 to 2016, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Madison County
Madison County25614.8%1.2 pCi/LThis county
North Carolina, pooled99 counties, pooled70,56623.2%Not pooled+8.4 points
United States, pooled2,666 counties, pooled1,939,02535.8%Not pooled+21.0 points
Transylvania Countyhighest in the state3,99648.1%3.7 pCi/L+33.3 points
Columbus Countylowest in the state320.0%0.1 pCi/L−14.8 points
Cocke County, TNborders it5450.0%3.9 pCi/L+35.2 points
Greene County, TNborders it35347.3%3.7 pCi/L+32.5 points
Unicoi County, TNborders it11738.5%2.9 pCi/L+23.7 points
Buncombe County, NCborders it6,67030.3%2.4 pCi/L+15.5 points
Haywood County, NCborders it1,95130.2%2.2 pCi/L+15.4 points
Yancey County, NCborders it32329.4%1.9 pCi/L+14.6 points
Where Madison County's reported results fell, 2007 to 2016, laboratory, beside North Carolina and the United States
ResultMadison County testsMadison County shareNorth Carolina shareU.S. shareAgainst North Carolina
Under 2 pCi/L16966.0%55.2%39.6%+10.8 points
2 to 4 pCi/L4919.1%21.6%24.6%−2.5 points
4 pCi/L and above3814.8%23.2%35.8%−8.4 points
Madison County ranked among the 73 North Carolina counties with 30 or more tests, by share at or above 4 pCi/L, 2007 to 2016, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Moore County42 of 739919.2%1.2 pCi/L
Rowan County43 of 7354618.3%1.4 pCi/L
Person County44 of 7317317.9%1.3 pCi/L
Macon County45 of 731,31317.6%1.3 pCi/L
Davie County46 of 7369316.7%1.7 pCi/L
Madison County47 of 7325614.8%1.2 pCi/L
Vance County48 of 7310313.6%1.6 pCi/L
Union County49 of 7381511.9%1.0 pCi/L
Orange County50 of 731,06311.6%1.1 pCi/L
Granville County51 of 7314810.8%0.7 pCi/L
Chatham County52 of 7355210.5%1.1 pCi/L
Madison County radon tests by year, against North Carolina's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNorth Carolina, pooledChange from the row before
202250.0%0.1 pCi/L1.0 pCi/L10.7%−7.4 points
2021277.4%0.1 pCi/L6.0 pCi/L14.9%−13.5 points
20208620.9%1.1 pCi/L33.0 pCi/L21.1%−19.1 points
20143540.0%3.0 pCi/L26.0 pCi/L21.9%First on file

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

Madison County, Geology

The ground under Madison County

Predicted

Most of the ground under Madison County is one class on USGS's geologic map: 99.9% of its land is moderate radon potential, with 0.1% high. 99.4% of it lies in the area the map calls Blue Ridge, to which USGS gives a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under Madison County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Blue RidgeGranite, pegmatite, monazite, schist, and gneiss.Moderate1099.4%

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

Madison County beside the ground around it

On high-potential ground Madison County is close to North Carolina as a whole: 0.1% of its land against 1.3%. Of the 6 counties that border it, 4 have more high-potential ground, Greene County, TN the most at 94.5%.

Share of land by USGS radon potential: Madison County, the 6 counties bordering it and North Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Madison CountyZone 2None99.9%0.1%
Buncombe CountyZone 1None88.0%12.0%
Unicoi County, TNZone 2None35.6%64.5%
Yancey CountyZone 2None100%None
Greene County, TNZone 1None5.5%94.5%
Cocke County, TNZone 2None32.9%67.1%
Haywood CountyZone 2None100%None
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

Madison County, Local resources

Radon testing and mitigation in Madison 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

Madison County, Questions

Questions about radon in Madison County

Are radon levels high in Madison County?

In 2022, 0.0% of the radon tests reported to CDC for Madison County, North Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.1 pCi/L. Of 73 North Carolina counties with 30 or more tests for the same period, 46 reported a higher share; pooled, the state comes to 23.2%.

Which counties border Madison County?

Madison County borders 6 counties: Buncombe County, NC, Unicoi County, TN, Yancey County, NC, Greene County, TN, Cocke County, TN and Haywood County, NC.

Products

Madison County, Products

Testing a home in Madison County

In Madison County, 14.8% of 256 tests reported to CDC over the 2007 to 2016 laboratory totals reached 4 pCi/L, against 23.2% pooled across North Carolina. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Madison County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Madison County homes, compared

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Madison County, Bordering counties

Counties bordering Madison County

Calculated by Radon411

Madison County, Cities and towns

Cities and towns in Madison County

Madison County is growing: the Census Bureau puts it at 22,553 residents on July 1, 2025, up 5.9% from 21,292 in 2020. That works out to 50 people per square mile of land. No town dominates: Mars Hill, the largest, has 2,280 residents, 10.1% of the total. Together its 3 incorporated places hold 16.1% of those residents; the other 83.9% live outside any of them. Testing is reported here more often than across the state: CDC's 256 reported tests for 2007 to 2016 come to 11.4 for every 1,000 residents (2025 estimate), against 6.3 for North Carolina.

From Mars Hill to Hot Springs, CDC publishes no figure by town: each reads Madison County's.

The cities and towns in Madison County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Mars Hill2,280+11.9%10.1%
Marshall802+2.3%3.6%
Hot Springs548+5.0%2.4%

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).

Madison County, Homes

Homes in Madison County

Of Madison County's 11,201 homes, 70% are detached houses, against 65% across North Carolina; 23% are mobile homes. Half of its homes were built before 1986, close to North Carolina's 1990: 20% date from before 1960 and 26% from 2000 or later. Owners live in 78% of the occupied homes (North Carolina: 66%), so for most households a test and a fix are their own to order.

Homes in Madison County, North Carolina, 2019 to 2023
HomesMadison CountyNorth Carolina
Housing units11,2014,815,195
Detached houses70%65%
In buildings of 5 or more3%14%
Mobile homes23%11%
Built before 196020%14%
Built since 200026%33%
Middle year built19861990
Owner-occupied78%66%

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