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Radon Levels in Lyon County, Kansas

EPA puts Lyon County in Zone 2, its middle radon zone, and 31.9% of its 47 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

    31.9%

    0.1 pts below KS

    Lyon
    31.9%
    Kansas
    32.0%

    47 tests, 2022

  • Median result

    2.5pCi/L

    Below action level

    Lyon
    2.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    47

    32nd of 38 by tests

    Lyon
    47
    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

    20 of 38

    Middle half

    Lyon
    31.9%
    Mitchell
    57.4%

    By share, of 38 with 30+ tests

Read a result for Lyon County

Starts at Lyon County's median, 2.5 pCi/L

2.5pCi/L

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

EPA’s reading of 2.5 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. Lyon County's median reported result, 2022.

Interpret this readingWhat a fix costs

The data

Lyon County, At a glance

Lyon County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Lyon 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 Lyon County, 2022

Share of reported tests at or above 4 pCi/L, by year, Lyon County
Share of reported tests at or above 4 pCi/L, by year, Lyon County
YearShare of reported tests at or above 4 pCi/L
201636.0%
201748.4%
201851.6%
201938.0%
202012.3%
202137.8%
202231.9%

2022: 31.9%. Across these years the share ran from 12.3% to 51.6%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 47 tests reported to CDC for Lyon 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

Lyon County, Compared

Lyon County radon figures, compared

Calculated by Radon411

In Lyon County, about 3 in 10 reported tests in 2022 (15 of 47) were at or above EPA's action level. Against the national pool of 23.9%, the gap is 8.0 points higher. Across 96 Kansas counties pooled together, 32.0% of tests reached that level, so Lyon County runs 0.1 points below its state.

Wabaunsee County, the one bordering county with a figure for the same period, reported 29.0%. By share, Lyon County is 20th of 38 Kansas counties with 30 or more tests for the same period.

Year by year, 2016 opened at 36.0% and 2022 closed at 31.9% (down 4.1 points), with 2018 the high at 51.6%. Half the tests came in under 2.5 pCi/L and half over it; the single highest reached 15.8 pCi/L. Below the action level, 17 tests (36.2%) came in under 2 pCi/L, against 45.8% statewide, and 15 tests (31.9%) 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 31.9% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential.

The busiest year on file was 2017, with 128 tests reported; the quietest, 2022, had 47.

Share of reported tests at or above 4 pCi/L by year, Lyon County against Kansas2016 to 2022, years with 30 or more tests: Lyon County 36.0% to 31.9%, the state's pooled share 32.0% in 2022.
Lyon CountyKansas, pooled
Share of reported tests at or above 4 pCi/L by year, Lyon County against Kansas: data table
YearTestsLyon County, at or above 4 pCi/LKansas, pooled
20168936.0%35.4%
201712848.4%37.3%
201812451.6%37.3%
20195038.0%33.7%
20206512.3%31.3%
202111137.8%31.8%
20224731.9%32.0%
Lyon County against Kansas, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Lyon County
Lyon County4731.9%2.5 pCi/LThis county
Kansas, pooled96 counties, pooled18,38532.0%Not pooled+0.1 points
United States, pooled853 counties, pooled333,14023.9%Not pooled−8.0 points
Mitchell Countyhighest in the state4757.4%6.2 pCi/L+25.5 points
Crawford Countylowest in the state345.9%0.8 pCi/L−26.0 points
Chase County, KSborders it366.7%4.4 pCi/L+34.8 points
Coffey County, KSborders it1656.3%5.0 pCi/L+24.4 points
Morris County, KSborders it2343.5%3.5 pCi/L+11.6 points
Osage County, KSborders it2642.3%3.5 pCi/L+10.4 points
Wabaunsee County, KSborders it3129.0%2.2 pCi/L−2.9 points
Greenwood County, KSborders it616.7%0.9 pCi/L−15.2 points
Where Lyon County's reported results fell, 2022, beside Kansas and the United States
ResultLyon County testsLyon County shareKansas shareU.S. shareAgainst Kansas
Under 2 pCi/L1736.2%45.8%54.5%−9.6 points
2 to 4 pCi/L1531.9%22.1%21.7%+9.8 points
4 pCi/L and above1531.9%32.0%23.9%−0.1 points
Lyon 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
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
Sumner County25 of 387929.1%2.3 pCi/L
Lyon County radon tests by year, against Kansas' pooled share
YearTestsAt or above 4 pCi/LMedianHighestKansas, pooledChange from the row before
20224731.9%2.5 pCi/L15.8 pCi/L32.0%−5.9 points
202111137.8%2.0 pCi/L48.1 pCi/L31.8%+25.5 points
20206512.3%1.2 pCi/L17.0 pCi/L31.3%−25.7 points
20195038.0%2.7 pCi/L13.9 pCi/L33.7%−13.6 points
201812451.6%4.0 pCi/L46.0 pCi/L37.3%+3.2 points
201712848.4%3.7 pCi/L39.5 pCi/L37.3%+12.4 points
20168936.0%3.0 pCi/L105.1 pCi/L35.4%First on file

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

Lyon County, Geology

The ground under Lyon County

Predicted

USGS's geologic map puts all of Lyon 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 Lyon 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.

Lyon County beside the ground around it

Across Kansas 59.9% of the land is rated high; none of Lyon County's is. Of the 6 counties that border it, 2 have more high-potential ground, Wabaunsee County the most at 37.6%.

Share of land by USGS radon potential: Lyon County, the 6 counties bordering it and Kansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Lyon CountyZone 2None100%None
Osage CountyZone 2None100%None
Chase CountyZone 2None100%None
Coffey CountyZone 2None100%None
Morris CountyZone 2None80.0%20.0%
Wabaunsee CountyZone 2None62.4%37.6%
Greenwood 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

Lyon County, Local resources

Radon testing and mitigation in Lyon County

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

What it means

Lyon County, Questions

Questions about radon in Lyon County

Are radon levels high in Lyon County?

In 2022, 31.9% of the radon tests reported to CDC for Lyon County, Kansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.5 pCi/L. Of 38 Kansas counties with 30 or more tests for the same period, 19 reported a higher share; pooled, the state comes to 32.0%.

Which counties border Lyon County?

Lyon County borders 6 counties: Osage County, Chase County, Coffey County, Morris County, Wabaunsee County and Greenwood County.

Products

Lyon County, Products

Testing a home in Lyon County

In Lyon County, 31.9% of 47 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 Lyon County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Lyon County homes, compared

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Lyon County, Bordering counties

Counties bordering Lyon County

Calculated by Radon411

Lyon County, Cities and towns

Cities and towns in Lyon County

Lyon County's population has barely moved since 2020: 32,266 residents on July 1, 2025 against 32,110 then, by the Census Bureau's estimates. That works out to 38 people per square mile of land. Emporia alone is home to 24,137 of them, 74.8% of the total. Together its 9 incorporated places hold 82.3% of those residents; the other 17.7% live outside any of them. Reported testing is thin here: 47 tests over 2022, or 1.5 for every 1,000 residents (2025 estimate), where Kansas as a whole comes to 6.2.

From Emporia to Bushong, CDC publishes no figure by town: each reads Lyon County's.

The cities and towns in Lyon County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Emporia24,137+0.1%74.8%
Americus782+0.8%2.4%
Olpe529+2.3%1.6%
Hartford360+1.7%1.1%
Neosho Rapids238+0.8%0.7%
Reading183+1.1%0.6%
Allen163+1.2%0.5%
Admire134+2.3%0.4%
Bushong28LevelUnder 0.1%

9 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).

Lyon County, Homes

Homes in Lyon County

Of Lyon County's 14,998 homes, 62% are detached houses, against 72% across Kansas; 19% are in buildings of five or more homes. Half of its homes were built before 1970, close to Kansas' 1975: 38% date from before 1960 and 12% from 2000 or later. 58% 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 Lyon County, Kansas, 2019 to 2023
HomesLyon CountyKansas
Housing units14,9981,285,221
Detached houses62%72%
In buildings of 5 or more19%13%
Mobile homes8%4%
Built before 196038%33%
Built since 200012%20%
Middle year built19701975
Owner-occupied58%67%

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