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Radon Levels in Allen County, Kansas

EPA puts Allen County in Zone 2, its middle radon zone, and most reported tests there come back low, though 8.8% of 34 (2022) reached 4 pCi/L. 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

    8.8%

    23.2 pts below KS

    Allen
    8.8%
    Kansas
    32.0%

    34 tests, 2022

  • Median result

    0.9pCi/L

    Below action level

    Allen
    0.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    34

    36th of 38 by tests

    Allen
    34
    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

    37 of 38

    Lowest quarter

    Allen
    8.8%
    Mitchell
    57.4%

    By share, of 38 with 30+ tests

Read a result for Allen County

Starts at Allen County's median, 0.9 pCi/L

0.9pCi/L

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

EPA’s reading of 0.9 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. Allen County's median reported result, 2022.

Interpret this reading

The data

Allen County, At a glance

Allen County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Allen 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 Allen County, 2022

Share of reported tests at or above 4 pCi/L, by year, Allen County
Share of reported tests at or above 4 pCi/L, by year, Allen County
YearShare of reported tests at or above 4 pCi/L
201666.7%
20170.0%
201862.5%
201914.3%
202011.1%
20210.0%
20228.8%

2022: 8.8%. Across these years the share ran from 0.0% to 66.7%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 34 tests reported to CDC for Allen 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

Allen County, Compared

Allen County radon figures, compared

Calculated by Radon411

Allen County reports fewer high tests than Kansas overall. 8.8% of its 34 tests in 2022 were at or above 4 pCi/L. That is 23.2 points below the 32.0% pooled from 96 Kansas counties.

Ordered from highest share down, it comes 37th of 38 Kansas counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 23.9%; Allen County sits 15.1 points below it.

The reported tests do not follow EPA's Zone 2 label for Allen County (predicted average between 2 and 4 pCi/L): 8.8% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 0.9 pCi/L and half over it; the single highest reached 47.4 pCi/L. The rest split 82.4% under 2 pCi/L and 8.8% from 2 to 4 (Kansas: 45.8% and 22.1%).

The busiest year on file was 2022, with 34 tests reported; the quietest, 2017, had 4.

Allen County against Kansas, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Allen County
Allen County348.8%0.9 pCi/LThis county
Kansas, pooled96 counties, pooled18,38532.0%Not pooled+23.2 points
United States, pooled853 counties, pooled333,14023.9%Not pooled+15.1 points
Mitchell Countyhighest in the state4757.4%6.2 pCi/L+48.6 points
Crawford Countylowest in the state345.9%0.8 pCi/L−2.9 points
Bourbon County, KSborders it757.1%4.6 pCi/L+48.3 points
Coffey County, KSborders it1656.3%5.0 pCi/L+47.5 points
Linn County, KSborders it1553.3%4.0 pCi/L+44.5 points
Anderson County, KSborders it1241.7%2.6 pCi/L+32.9 points
Wilson County, KSborders it825.0%1.9 pCi/L+16.2 points
Neosho County, KSborders it520.0%3.0 pCi/L+11.2 points
Woodson County, KSborders it10.0%1.4 pCi/L−8.8 points
Where Allen County's reported results fell, 2022, beside Kansas and the United States
ResultAllen County testsAllen County shareKansas shareU.S. shareAgainst Kansas
Under 2 pCi/L2882.4%45.8%54.5%+36.6 points
2 to 4 pCi/L38.8%22.1%21.7%−13.3 points
4 pCi/L and above38.8%32.0%23.9%−23.2 points
Allen 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
Leavenworth County28 of 3851526.8%1.9 pCi/L
Douglas County29 of 3886825.8%1.8 pCi/L
Butler County30 of 3855025.5%2.1 pCi/L
Reno County31 of 3824025.4%2.2 pCi/L
Pottawatomie County32 of 3820625.2%1.7 pCi/L
Geary County33 of 3836525.2%1.9 pCi/L
Finney County34 of 387623.7%3.0 pCi/L
Sedgwick County35 of 384,91118.4%1.3 pCi/L
Montgomery County36 of 386911.6%0.8 pCi/L
Allen County37 of 38348.8%0.9 pCi/L
Crawford County38 of 38345.9%0.8 pCi/L
Allen County radon tests by year, against Kansas' pooled share
YearTestsAt or above 4 pCi/LMedianHighestKansas, pooledChange from the row before
2022348.8%0.9 pCi/L47.4 pCi/L32.0%+8.8 points
202160.0%2.1 pCi/L3.0 pCi/L31.8%−11.1 points
2020911.1%2.4 pCi/L4.0 pCi/L31.3%−3.2 points
2019714.3%0.6 pCi/L42.6 pCi/L33.7%−48.2 points
2018862.5%4.7 pCi/L7.9 pCi/L37.3%+62.5 points
201740.0%1.5 pCi/L2.5 pCi/L37.3%−66.7 points
2016666.7%4.4 pCi/L5.1 pCi/L35.4%First on file

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

Allen County, Geology

The ground under Allen County

Predicted

USGS's geologic map puts all of Allen 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 Allen 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.

Allen County beside the ground around it

Across Kansas 59.9% of the land is rated high; none of Allen County's is. Of the 7 counties that border it, none has as large a share of moderate-potential ground; Anderson County comes nearest at 100%.

Share of land by USGS radon potential: Allen County, the 7 counties bordering it and Kansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Allen CountyZone 2None100%None
Anderson CountyZone 2None100%None
Woodson CountyZone 2None100%None
Bourbon CountyZone 2None100%None
Neosho CountyZone 2None100%None
Linn CountyZone 2None100%None
Coffey CountyZone 2None100%None
Wilson 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

Allen County, Local resources

Radon testing and mitigation in Allen County

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

What it means

Allen County, Questions

Questions about radon in Allen County

Are radon levels high in Allen County?

In 2022, 8.8% of the radon tests reported to CDC for Allen County, Kansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of 38 Kansas counties with 30 or more tests for the same period, 36 reported a higher share; pooled, the state comes to 32.0%.

Which counties border Allen County?

Allen County borders 7 counties: Anderson County, Woodson County, Bourbon County, Neosho County, Linn County, Coffey County and Wilson County.

Products

Allen County, Products

Testing a home in Allen County

In Allen County, 8.8% of 34 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 Allen County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Allen County homes, compared

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Allen County, Bordering counties

Counties bordering Allen County

Calculated by Radon411

Allen County, Cities and towns

Cities and towns in Allen County

About 12,302 people live in Allen County by the Census Bureau's estimate for July 1, 2025, 231 fewer than in 2020 (−1.8%). That works out to 25 people per square mile of land. Its largest town, Iola, has 5,240 residents, 42.6% of the total. Together its 8 incorporated places hold 69.9% of those residents; the other 30.1% live outside any of them. Reported testing is thin here: 34 tests over 2022, or 2.8 for every 1,000 residents (2025 estimate), where Kansas as a whole comes to 6.2.

From Iola to Bassett, CDC publishes no figure by town: each reads Allen County's.

The cities and towns in Allen County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Iola5,240−3.0%42.6%
Humboldt1,807−2.2%14.7%
La Harpe481−0.8%3.9%
Gas467−1.3%3.8%
Moran455−2.2%3.7%
Savonburg75Level0.6%
Elsmore52−1.9%0.4%
Bassett20−4.8%0.2%

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).

Allen County, Homes

Homes in Allen County

Allen County is a place of houses on their own lots: 82% of its 6,077 homes are detached single-family houses, against 72% across Kansas. The homes are older than Kansas' as a whole: half were built before 1965 (1975 for Kansas), and 45% date from before 1960. 75% 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 Allen County, Kansas, 2019 to 2023
HomesAllen CountyKansas
Housing units6,0771,285,221
Detached houses82%72%
In buildings of 5 or more4%13%
Mobile homes9%4%
Built before 196045%33%
Built since 20009%20%
Middle year built19651975
Owner-occupied75%67%

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