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Radon Levels in Franklin County, Tennessee

EPA puts Franklin County in Zone 3, its lowest radon zone, and only 8 radon tests from it are on file with CDC (2023). 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

    25.6%

    7.7 pts below TN

    Franklin
    25.6%
    Tennessee
    33.3%

    266 tests, 2008 to 2017

  • Median result

    2.1pCi/L

    Below action level

    Franklin
    2.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    266

    23rd of 80 by tests

    Franklin
    266
    Davidson
    5,592

    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 Tennessee

    50 of 80

    Middle half

    Franklin
    25.6%
    Jefferson
    56.8%

    By share, of 80 with 30+ tests

Read a result for Franklin County

Starts at Franklin County's median, 2.1 pCi/L

2.1pCi/L

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

EPA’s reading of 2.1 pCi/L

Between 2 and 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Franklin County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Franklin County, At a glance

Franklin County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Franklin 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 86% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Franklin County, 2023

Share of reported tests at or above 4 pCi/L, by year, Franklin County
Share of reported tests at or above 4 pCi/L, by year, Franklin County
YearShare of reported tests at or above 4 pCi/L
202240.0%
202312.5%

2023: 12.5%. Across these years the share ran from 12.5% to 40.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 8 tests were reported to CDC for Franklin County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

Franklin County, Compared

Franklin County radon figures, compared

Calculated by Radon411

Franklin County's 266 reported tests over the 2008 to 2017 laboratory totals had a middle value of 2.1 pCi/L and a maximum of 83.7 pCi/L, and 25.6% reached 4 pCi/L. Tennessee as a whole (95 Tennessee counties, pooled) comes to 33.3%: 7.7 points higher than here.

The newest figure, in 2023, counts only 8 tests (12.5% at or above 4 pCi/L), too few to compare, so this reading uses the 266-test figure.

Among its state's counties it ranks 50th of 80 Tennessee counties with 30 or more tests for the same period. Statewide for the same period, Jefferson County reported the highest share (56.8%) and Chester County the lowest (0.0%).

Below the action level, 121 tests (45.5%) came in under 2 pCi/L, against 42.4% statewide, and 77 tests (28.9%) fell between 2 and 4, against 24.3% statewide. The busiest year on file was 2022, with 30 tests reported; the quietest, 2023, had 8.

EPA's 1993 zone map puts Franklin County in Zone 3, a predicted county average under 2 pCi/L. USGS geology rates 86% of the county's land moderate radon potential.

Next door, the shares run from 16.5% in Coffee County to 35.3% in Moore County, with Madison County, AL, Lincoln County and Jackson County, AL below Franklin County.

CDC also counts 5 tests taken after mitigation in Franklin County for the same period: tests in homes where a fix was already in.

Franklin County against Tennessee, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Franklin County
Franklin County26625.6%2.1 pCi/LThis county
Tennessee, pooled95 counties, pooled31,06633.3%Not pooled+7.7 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+10.1 points
Jefferson Countyhighest in the state14656.8%4.7 pCi/L+31.2 points
Chester Countylowest in the state440.0%1.1 pCi/L−25.6 points
Moore County, TNborders it5135.3%2.9 pCi/L+9.7 points
Marion County, TNborders it7428.4%1.6 pCi/L+2.8 points
Madison County, ALborders it5,17825.2%1.9 pCi/L−0.4 points
Lincoln County, TNborders it14920.8%1.9 pCi/L−4.8 points
Jackson County, ALborders it22317.5%1.5 pCi/L−8.1 points
Coffee County, TNborders it20616.5%1.3 pCi/L−9.1 points
Grundy County, TNborders it290.0%1.0 pCi/L−25.6 points
Where Franklin County's reported results fell, 2008 to 2017, laboratory, beside Tennessee and the United States
ResultFranklin County testsFranklin County shareTennessee shareU.S. shareAgainst Tennessee
Under 2 pCi/L12145.5%42.4%39.6%+3.1 points
2 to 4 pCi/L7728.9%24.3%24.7%+4.6 points
4 pCi/L and above6825.6%33.3%35.7%−7.7 points
Franklin County ranked among the 80 Tennessee counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Rhea County45 of 804526.7%2.4 pCi/L
Dickson County46 of 8020926.3%2.1 pCi/L
Stewart County46 of 809526.3%2.1 pCi/L
Sumner County48 of 801,31126.0%1.9 pCi/L
Williamson County49 of 803,41425.8%2.0 pCi/L
Franklin County50 of 8026625.6%2.1 pCi/L
Bledsoe County51 of 803724.3%2.1 pCi/L
Humphreys County52 of 8010523.8%2.0 pCi/L
Lawrence County53 of 8013621.3%1.6 pCi/L
Bedford County54 of 8012421.0%1.8 pCi/L
Bradley County55 of 8042520.9%1.9 pCi/L
Franklin County radon tests by year, against Tennessee's pooled share
YearTestsAt or above 4 pCi/LMedianHighestTennessee, pooledChange from the row before
2023812.5%2.8 pCi/L4.4 pCi/L24.9%−27.5 points
20223040.0%2.3 pCi/L22.1 pCi/L23.8%First on file

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

Franklin County, Geology

The ground under Franklin County

Predicted

Most of the ground under Franklin County is one class on USGS's geologic map: 86.0% of its land is moderate radon potential, with 5.8% high and 8.2% low. The map puts 86.0% of Franklin County in the area it calls Highland Rim and 8.2% in Appalachian Plateau, with one smaller area beside them. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 8, in the low band (5 to 8).

USGS's geologic areas under Franklin County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Highland RimPaleozoic sedimentary rocks (limestone, shale, chert, and dolostone).Moderate1186.0%
Appalachian PlateauSandstone and shale.Low88.2%
Nashville BasinMississippian Limestone.High145.5%

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

Franklin County beside the ground around it

Tennessee as a whole has more high-potential ground than Franklin County: 47.2% of its land, against 5.8% here. Of the 7 counties that border it, 6 have more high-potential ground, Madison County, AL the most at 100%.

Share of land by USGS radon potential: Franklin County, the 7 counties bordering it and Tennessee
AreaEPA zoneLow potentialModerate potentialHigh potential
Franklin CountyZone 38.2%86.0%5.8%
Moore CountyZone 1None29.0%71.0%
Coffee CountyZone 2None87.8%12.2%
Marion CountyZone 250.7%None49.3%
Grundy CountyZone 369.0%30.2%0.8%
Lincoln CountyZone 1None29.8%70.2%
Jackson County, ALZone 11.1%14.2%84.8%
Madison County, ALZone 1NoneNone100%
Tennessee95 counties, pooled by land areaVaries30.5%22.3%47.2%

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

Local help

Franklin County, Local resources

Radon testing and mitigation in Franklin County

What Tennessee's program says
Phone
1-800-232-1139
Email
TDEC.Radon@tn.gov

What it means

Franklin County, Questions

Questions about radon in Franklin County

Are radon levels high in Franklin County?

In 2023, 12.5% of the radon tests reported to CDC for Franklin County, Tennessee were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.8 pCi/L. Of 80 Tennessee counties with 30 or more tests for the same period, 49 reported a higher share; pooled, the state comes to 33.3%.

Which counties border Franklin County?

Franklin County borders 7 counties: Moore County, TN, Coffee County, TN, Marion County, TN, Grundy County, TN, Lincoln County, TN, Jackson County, AL and Madison County, AL.

Products

Franklin County, Products

Testing a home in Franklin County

In Franklin County, 25.6% of 266 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 33.3% pooled across Tennessee. 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 Franklin County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Franklin County homes, compared

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Franklin County, Bordering counties

Counties bordering Franklin County

Calculated by Radon411

Franklin County, Cities and towns

Cities and towns in Franklin County

Franklin County is growing: the Census Bureau puts it at 45,579 residents on July 1, 2025, up 6.4% from 42,842 in 2020. That works out to 82 people per square mile of land. Tullahoma, the largest place on its list (21,279 residents in all), extends beyond Franklin County, so no share of the total is worked out for it. CDC's 266 reported tests for 2008 to 2017 work out to 5.8 per 1,000 residents (2025 estimate), close to Tennessee's 4.2.

From Tullahoma to Huntland, CDC publishes no figure by town: each reads Franklin County's.

The cities and towns in Franklin County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Tullahomaextends beyond Franklin County21,279+4.3%Counted whole
Winchester10,438+10.8%22.9%
Estill Springs2,692−0.4%5.9%
Decherd2,499+5.3%5.5%
Cowan1,799+1.8%3.9%
Monteagleextends beyond Franklin County1,439+3.9%Counted whole
Huntland887Level1.9%

7 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). A place that extends beyond Franklin County is counted whole, so it has no share.

Franklin County, Homes

Homes in Franklin County

Franklin County is a place of houses on their own lots: 81% of its 19,815 homes are detached single-family houses, against 68% across Tennessee. Half of its homes were built before 1984, close to Tennessee's 1986: 19% date from before 1960 and 24% from 2000 or later. Owners live in 76% of the occupied homes (Tennessee: 67%), so for most households a test and a fix are their own to order.

Homes in Franklin County, Tennessee, 2019 to 2023
HomesFranklin CountyTennessee
Housing units19,8153,095,472
Detached houses81%68%
In buildings of 5 or more2%14%
Mobile homes9%8%
Built before 196019%18%
Built since 200024%29%
Middle year built19841986
Owner-occupied76%67%

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