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Radon Levels in Franklin County, Kansas

EPA puts Franklin County in Zone 2, its middle radon zone, and 34.0% of its 106 reported radon tests (2022) were at or above 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

    34.0%

    2.0 pts above KS

    Franklin
    34.0%
    Kansas
    32.0%

    106 tests, 2022

  • Median result

    2.1pCi/L

    Below action level

    Franklin
    2.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    106

    19th of 38 by tests

    Franklin
    106
    Johnson
    5,240

    Reported to CDC before any fix, 2022

  • 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 Kansas

    19 of 38

    Middle half

    Franklin
    34.0%
    Mitchell
    57.4%

    By share, of 38 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, 2022.

Interpret this readingWhat a fix costs

The data

Franklin County, At a glance

Franklin County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Franklin 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 Franklin County, 2022

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
201626.8%
201728.6%
201832.9%
201921.2%
202031.3%
202134.0%
202234.0%

2022: 34.0%. Across these years the share ran from 21.2% to 34.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 106 tests reported to CDC for Franklin County over 2022, 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: 2022. Measured data period: 2016 to 2022 (every CDC figure on file).

How to read these figures

Franklin County, Compared

Franklin County radon figures, compared

Calculated by Radon411

In Franklin County, about 3 in 10 reported tests in 2022 (36 of 106) were at or above EPA's action level. Against the national pool of 23.9%, the gap is 10.1 points higher. Across 96 Kansas counties pooled together, 32.0% of tests reached that level, so Franklin County runs 2.0 points above its state.

Of 3 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 25.8% (Douglas County) to 41.2% (Johnson County). By share, Franklin County is 19th of 38 Kansas counties with 30 or more tests for the same period.

Year by year, 2016 opened at 26.8% and 2022 closed at 34.0% (up 7.2 points), with 2021 the high at 34.0%. Half the tests came in under 2.1 pCi/L and half over it; the single highest reached 47.1 pCi/L. Below the action level, 49 tests (46.2%) came in under 2 pCi/L, against 45.8% statewide, and 21 tests (19.8%) fell between 2 and 4, against 22.1% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 34.0% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential.

The busiest year on file was 2021, with 300 tests reported; the quietest, 2016, had 56.

Share of reported tests at or above 4 pCi/L by year, Franklin County against Kansas2016 to 2022, years with 30 or more tests: Franklin County 26.8% to 34.0%, the state's pooled share 32.0% in 2022.
Franklin CountyKansas, pooled
Share of reported tests at or above 4 pCi/L by year, Franklin County against Kansas: data table
YearTestsFranklin County, at or above 4 pCi/LKansas, pooled
20165626.8%35.4%
20177028.6%37.3%
20187932.9%37.3%
201911321.2%33.7%
20209631.3%31.3%
202130034.0%31.8%
202210634.0%32.0%
Franklin County against Kansas, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Franklin County
Franklin County10634.0%2.1 pCi/LThis county
Kansas, pooled96 counties, pooled18,38532.0%Not pooled−2.0 points
United States, pooled853 counties, pooled333,14023.9%Not pooled−10.1 points
Mitchell Countyhighest in the state4757.4%6.2 pCi/L+23.4 points
Crawford Countylowest in the state345.9%0.8 pCi/L−28.1 points
Coffey County, KSborders it1656.3%5.0 pCi/L+22.3 points
Linn County, KSborders it1553.3%4.0 pCi/L+19.3 points
Osage County, KSborders it2642.3%3.5 pCi/L+8.3 points
Anderson County, KSborders it1241.7%2.6 pCi/L+7.7 points
Johnson County, KSborders it5,24041.2%3.0 pCi/L+7.2 points
Miami County, KSborders it21440.2%3.0 pCi/L+6.2 points
Douglas County, KSborders it86825.8%1.8 pCi/L−8.2 points
Where Franklin County's reported results fell, 2022, beside Kansas and the United States
ResultFranklin County testsFranklin County shareKansas shareU.S. shareAgainst Kansas
Under 2 pCi/L4946.2%45.8%54.5%+0.4 points
2 to 4 pCi/L2119.8%22.1%21.7%−2.3 points
4 pCi/L and above3634.0%32.0%23.9%+2.0 points
Franklin County ranked among the 38 Kansas counties with 30 or more tests, by share at or above 4 pCi/L, 2022
CountyRankTestsAt or above 4 pCi/LMedian
Jefferson County14 of 385339.6%2.4 pCi/L
Dickinson County15 of 3811338.9%2.7 pCi/L
Ford County16 of 385036.0%3.8 pCi/L
Shawnee County17 of 3838834.5%2.6 pCi/L
Harvey County18 of 3823234.1%2.8 pCi/L
Franklin County19 of 3810634.0%2.1 pCi/L
Lyon County20 of 384731.9%2.5 pCi/L
Marshall County21 of 386631.8%1.9 pCi/L
Riley County22 of 3880031.3%1.9 pCi/L
Ellis County23 of 3819129.8%2.6 pCi/L
Wyandotte County24 of 3868729.7%2.1 pCi/L
Franklin County radon tests by year, against Kansas' pooled share
YearTestsAt or above 4 pCi/LMedianHighestKansas, pooledChange from the row before
202210634.0%2.1 pCi/L47.1 pCi/L32.0%Level
202130034.0%2.3 pCi/L27.1 pCi/L31.8%+2.7 points
20209631.3%2.3 pCi/L14.8 pCi/L31.3%+10.1 points
201911321.2%1.2 pCi/L15.2 pCi/L33.7%−11.7 points
20187932.9%2.1 pCi/L31.9 pCi/L37.3%+4.3 points
20177028.6%2.5 pCi/L20.5 pCi/L37.3%+1.8 points
20165626.8%2.3 pCi/L16.0 pCi/L35.4%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

USGS's geologic map puts all of Franklin County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Glaciated Area, to which USGS gives a radon index of 9, in the moderate band (9 to 11).

USGS's geologic areas under Franklin County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Glaciated AreaGlacial till underlain by Pennsylvanian and Permian marine and nonmarine sedimentary shale, sandstone, limestone, coal.Moderate9100%

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

Across Kansas 59.9% of the land is rated high; none of Franklin County's is. Of the 7 counties that border it, 2 have more high-potential ground, Johnson County the most at 97.6%.

Share of land by USGS radon potential: Franklin County, the 7 counties bordering it and Kansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Franklin CountyZone 2None100%None
Osage CountyZone 2None100%None
Douglas CountyZone 1None100%None
Miami CountyZone 2None68.6%31.4%
Anderson CountyZone 2None100%None
Coffey CountyZone 2None100%None
Johnson CountyZone 1None2.4%97.6%
Linn CountyZone 2None100%None
Kansas105 counties, pooled by land areaVariesNone40.1%59.9%

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 Kansas's program says
Phone
(800) 693-5343

What it means

Franklin County, Questions

Questions about radon in Franklin County

Are radon levels high in Franklin County?

In 2022, 34.0% of the radon tests reported to CDC for Franklin County, Kansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.1 pCi/L. Of 38 Kansas counties with 30 or more tests for the same period, 18 reported a higher share; pooled, the state comes to 32.0%.

Which counties border Franklin County?

Franklin County borders 7 counties: Osage County, Douglas County, Miami County, Anderson County, Coffey County, Johnson County and Linn County.

Products

Franklin County, Products

Testing a home in Franklin County

In Franklin County, 34.0% of 106 tests reported to CDC in 2022 reached 4 pCi/L, against 32.0% pooled across Kansas. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Franklin County; a long-term test tells the year-round average.

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

The Census Bureau estimates 26,299 residents in Franklin County for July 1, 2025, 285 more than in 2020 (+1.1%). That works out to 46 people per square mile of land. Its largest town, Ottawa, has 12,716 residents, 48.4% of the total. Together its 8 incorporated places hold 65.0% of those residents; the other 35.0% live outside any of them. Reported testing is thin here: 106 tests over 2022, or 4.0 for every 1,000 residents (2025 estimate), where Kansas as a whole comes to 6.2.

From Ottawa to Rantoul, 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
Ottawa12,716+0.7%48.4%
Wellsville2,002+2.8%7.6%
Pomona882−0.7%3.4%
Richmond440−2.4%1.7%
Williamsburg383−1.5%1.5%
Princeton255+3.2%1.0%
Lane244+1.7%0.9%
Rantoul172+1.8%0.7%

8 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).

Franklin County, Homes

Homes in Franklin County

Franklin County is a place of houses on their own lots: 77% of its 11,239 homes are detached single-family houses, against 72% across Kansas. Half of its homes were built before 1974, close to Kansas' 1975: 34% date from before 1960 and 18% from 2000 or later. 73% of occupied homes are lived in by their owner (Kansas: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Franklin County, Kansas, 2019 to 2023
HomesFranklin CountyKansas
Housing units11,2391,285,221
Detached houses77%72%
In buildings of 5 or more6%13%
Mobile homes9%4%
Built before 196034%33%
Built since 200018%20%
Middle year built19741975
Owner-occupied73%67%

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