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Radon Levels in Ellis County, Kansas

EPA puts Ellis County in Zone 1, its highest radon zone, and 29.8% of its 191 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

    29.8%

    2.2 pts below KS

    Ellis
    29.8%
    Kansas
    32.0%

    191 tests, 2022

  • Median result

    2.6pCi/L

    Below action level

    Ellis
    2.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    191

    16th of 38 by tests

    Ellis
    191
    Johnson
    5,240

    Reported to CDC before any fix, 2022

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Kansas

    23 of 38

    Middle half

    Ellis
    29.8%
    Mitchell
    57.4%

    By share, of 38 with 30+ tests

Read a result for Ellis County

Starts at Ellis County's median, 2.6 pCi/L

2.6pCi/L

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

EPA’s reading of 2.6 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. Ellis County's median reported result, 2022.

Interpret this readingWhat a fix costs

The data

Ellis County, At a glance

Ellis County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Ellis County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: High across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Ellis County, 2022

Share of reported tests at or above 4 pCi/L, by year, Ellis County
Share of reported tests at or above 4 pCi/L, by year, Ellis County
YearShare of reported tests at or above 4 pCi/L
201655.4%
201733.2%
201851.5%
201941.6%
202046.1%
202143.5%
202229.8%

2022: 29.8%. Across these years the share ran from 29.8% to 55.4%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 191 tests reported to CDC for Ellis 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

Ellis County, Compared

Ellis County radon figures, compared

Calculated by Radon411

Ellis County's 191 reported tests in 2022 had a middle value of 2.6 pCi/L and a maximum of 27.1 pCi/L, and 29.8% reached 4 pCi/L. Kansas as a whole (96 Kansas counties, pooled) comes to 32.0%: 2.2 points higher than here.

Among its state's counties it ranks 23rd of 38 Kansas counties with 30 or more tests for the same period. Statewide for the same period, Mitchell County reported the highest share (57.4%) and Crawford County the lowest (5.9%).

Below the action level, 67 tests (35.1%) came in under 2 pCi/L, against 45.8% statewide, and 67 tests (35.1%) fell between 2 and 4, against 22.1% statewide. The busiest year on file was 2021, with 780 tests reported; the quietest, 2016, had 148.

EPA's 1993 zone map puts Ellis County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.

Over 7 years of annual figures the share fell 25.6 points, from 55.4% in 2016 to 29.8% in 2022; its peak was 55.4% in 2016.

CDC also counts 10 tests taken after mitigation in Ellis County for the same period: tests in homes where a fix was already in.

Share of reported tests at or above 4 pCi/L by year, Ellis County against Kansas2016 to 2022, years with 30 or more tests: Ellis County 55.4% to 29.8%, the state's pooled share 32.0% in 2022.
Ellis CountyKansas, pooled
Share of reported tests at or above 4 pCi/L by year, Ellis County against Kansas: data table
YearTestsEllis County, at or above 4 pCi/LKansas, pooled
201614855.4%35.4%
201731933.2%37.3%
201820451.5%37.3%
201920941.6%33.7%
202028046.1%31.3%
202178043.5%31.8%
202219129.8%32.0%
Ellis County against Kansas, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Ellis County
Ellis County19129.8%2.6 pCi/LThis county
Kansas, pooled96 counties, pooled18,38532.0%Not pooled+2.2 points
United States, pooled853 counties, pooled333,14023.9%Not pooled−5.9 points
Mitchell Countyhighest in the state4757.4%6.2 pCi/L+27.6 points
Crawford Countylowest in the state345.9%0.8 pCi/L−23.9 points
Trego County, KSborders it683.3%5.6 pCi/L+53.5 points
Osborne County, KSborders it2382.6%7.4 pCi/L+52.8 points
Russell County, KSborders it2075.0%7.5 pCi/L+45.2 points
Ness County, KSborders it2669.2%10.2 pCi/L+39.4 points
Rooks County, KSborders it560.0%4.0 pCi/L+30.2 points
Rush County, KSborders it333.3%3.4 pCi/L+3.5 points
Where Ellis County's reported results fell, 2022, beside Kansas and the United States
ResultEllis County testsEllis County shareKansas shareU.S. shareAgainst Kansas
Under 2 pCi/L6735.1%45.8%54.5%−10.7 points
2 to 4 pCi/L6735.1%22.1%21.7%+13.0 points
4 pCi/L and above5729.8%32.0%23.9%−2.2 points
Ellis 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
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
Wabaunsee County26 of 383129.0%2.2 pCi/L
Rice County27 of 385328.3%1.8 pCi/L
Leavenworth County28 of 3851526.8%1.9 pCi/L
Ellis County radon tests by year, against Kansas' pooled share
YearTestsAt or above 4 pCi/LMedianHighestKansas, pooledChange from the row before
202219129.8%2.6 pCi/L27.1 pCi/L32.0%−13.7 points
202178043.5%3.5 pCi/L61.0 pCi/L31.8%−2.6 points
202028046.1%3.7 pCi/L17.8 pCi/L31.3%+4.5 points
201920941.6%3.3 pCi/L44.7 pCi/L33.7%−9.9 points
201820451.5%4.0 pCi/L38.5 pCi/L37.3%+18.3 points
201731933.2%2.4 pCi/L74.0 pCi/L37.3%−22.2 points
201614855.4%4.5 pCi/L18.5 pCi/L35.4%First on file

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

Ellis County, Geology

The ground under Ellis County

Predicted

USGS's geologic map puts all of Ellis County's mapped land in one class: high radon potential. The map puts 94.2% of Ellis County in the area it calls Smoky Hills and 5.8% in Ogallala Formation. USGS gives both a radon index of 12, in the high band (12 to 17).

USGS's geologic areas under Ellis County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Smoky HillsCretaceous marine sandstone, shale, and siltstone covered by discontinuous loess deposits.High1294.2%
Ogallala FormationTertiary sandstone, in part covered by windblown eolian sand and loess deposits.High125.8%

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

Ellis County beside the ground around it

Ellis County has more high-potential ground than Kansas as a whole: 100% of its land against 59.9%. Of the 6 counties that border it, none has as large a share of high-potential ground; Osborne County comes nearest at 100%.

Share of land by USGS radon potential: Ellis County, the 6 counties bordering it and Kansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Ellis CountyZone 1NoneNone100%
Rooks CountyZone 1NoneNone100%
Russell CountyZone 1NoneNone100%
Trego CountyZone 1NoneNone100%
Rush CountyZone 1NoneNone100%
Osborne CountyZone 1NoneNone100%
Ness CountyZone 1NoneNone100%
Kansas105 counties, pooled by land areaVariesNone40.1%59.9%

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

Local help

Ellis County, Local resources

Radon testing and mitigation in Ellis County

Listed radon businesses with an address in Ellis County:

Listed radon professionals by town: Hays

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

What it means

Ellis County, Questions

Questions about radon in Ellis County

Are radon levels high in Ellis County?

In 2022, 29.8% of the radon tests reported to CDC for Ellis County, Kansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.6 pCi/L. Of 38 Kansas counties with 30 or more tests for the same period, 22 reported a higher share; pooled, the state comes to 32.0%.

Which counties border Ellis County?

Ellis County borders 6 counties: Rooks County, Russell County, Trego County, Rush County, Osborne County and Ness County.

Products

Ellis County, Products

Testing a home in Ellis County

In Ellis County, 29.8% of 191 tests reported to CDC in 2022 reached 4 pCi/L, against 32.0% pooled across Kansas. In Zone 1 the year-round level in Ellis County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Ellis County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Ellis County

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Ellis County, Bordering counties

Counties bordering Ellis County

Calculated by Radon411

Ellis County, Cities and towns

Cities and towns in Ellis County

Ellis County's population has barely moved since 2020: 29,075 residents on July 1, 2025 against 28,951 then, by the Census Bureau's estimates. That works out to 32 people per square mile of land. Hays alone is home to 21,258 of them, 73.1% of the total. Together its 4 incorporated places hold 84.2% of those residents; the other 15.8% live outside any of them. CDC's 191 reported tests for 2022 work out to 6.6 per 1,000 residents (2025 estimate), close to Kansas' 6.2.

From Hays to Schoenchen, CDC publishes no figure by town: each reads Ellis County's.

The cities and towns in Ellis County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Hays21,258+0.5%73.1%
Ellis1,917−1.9%6.6%
Victoria1,134+0.2%3.9%
Schoenchen171+0.6%0.6%

4 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).

Ellis County, Homes

Homes in Ellis County

Of Ellis County's 13,247 homes, 71% are detached houses, against 72% across Kansas; 9% are in buildings of five or more homes. Half of its homes were built before 1972, close to Kansas' 1975: 32% date from before 1960 and 16% from 2000 or later. 62% 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 Ellis County, Kansas, 2019 to 2023
HomesEllis CountyKansas
Housing units13,2471,285,221
Detached houses71%72%
In buildings of 5 or more9%13%
Mobile homes4%4%
Built before 196032%33%
Built since 200016%20%
Middle year built19721975
Owner-occupied62%67%

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