Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Clay County, Kansas
EPA puts Clay County in Zone 1, its highest radon zone, and high results are common there: 55.8% of the 77 radon tests reported to CDC (2022) came back 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
Share at 4+ pCi/L
55.8%
23.8 pts above KS
- Clay
- 55.8%
- Kansas
- 32.0%
77 tests, 2022
Median result
4.8pCi/L
Action level reached
- Clay
- 4.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2022
Tests reported
77
22nd of 38 by tests
- Clay
- 77
- Johnson
- 5,240
Reported to CDC before any fix, 2022
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Kansas
2 of 38
Top quarter
- Clay
- 55.8%
- Mitchell
- 57.4%
By share, of 38 with 30+ tests
Read a result for Clay County
Starts at Clay County's median, 4.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.8 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Clay County's median reported result, 2022.
The data
Clay County, At a glance
Clay County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Clay County in
USGS geologic potential: High across 65% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Clay County, 2022
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2016 | 63.5% |
| 2017 | 53.9% |
| 2018 | 52.9% |
| 2019 | 34.1% |
| 2020 | 57.8% |
| 2021 | 54.0% |
| 2022 | 55.8% |
2022: 55.8%. Across these years the share ran from 34.1% to 63.5%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 77 tests reported to CDC for Clay 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).
Clay County, Compared
Clay County radon figures, compared
Calculated by Radon411More than half: 55.8% of the 77 radon tests reported to CDC for Clay County in 2022 read at least 4 pCi/L. That places it 2nd of 38 Kansas counties with 30 or more tests for the same period. That is 23.8 points above the 32.0% pooled from 96 Kansas counties.
The median result, 4.8 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 30.9 pCi/L. The rest split 20.8% under 2 pCi/L and 23.4% from 2 to 4 (Kansas: 45.8% and 22.1%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 55.8% share point the same way here.
No bordering county with a figure for the same period reported a higher share; the closest is Cloud County at 54.6%, the lowest Geary County at 25.2%. Statewide for the same period, Mitchell County reported the highest share (57.4%) and Crawford County the lowest (5.9%).
The busiest year on file was 2021, with 378 tests reported; the quietest, 2018, had 68.
Over 7 years of annual figures the share fell 7.7 points, from 63.5% in 2016 to 55.8% in 2022; its peak was 63.5% in 2016. Nationally, every county with a figure for the same period pools to 23.9%; Clay County sits 31.9 points above it. CDC also counts 18 tests taken after mitigation in Clay County for the same period: tests in homes where a fix was already in.
Clay CountyKansas, pooled
55.8% % of tests32.0% % of tests
| Year | Tests | Clay County, at or above 4 pCi/L | Kansas, pooled |
|---|---|---|---|
| 2016 | 96 | 63.5% | 35.4% |
| 2017 | 102 | 53.9% | 37.3% |
| 2018 | 68 | 52.9% | 37.3% |
| 2019 | 82 | 34.1% | 33.7% |
| 2020 | 116 | 57.8% | 31.3% |
| 2021 | 378 | 54.0% | 31.8% |
| 2022 | 77 | 55.8% | 32.0% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Clay County, Geology
The ground under Clay County
PredictedUSGS's geologic map splits Clay County: 65.3% of its land is high radon potential and 34.7% moderate. The map puts 37.8% of Clay County in the area it calls Smoky Hills and 34.7% in Glaciated Area, with one smaller area beside them. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Smoky Hills | Cretaceous marine sandstone, shale, and siltstone covered by discontinuous loess deposits. | High | 12 | 37.8% |
| Glaciated Area | Glacial till underlain by Pennsylvanian and Permian marine and nonmarine sedimentary shale, sandstone, limestone, coal. | Moderate | 9 | 34.7% |
| Mid-Continent Rift Zone | Faulted and fractured Permian limestone, dolomite, shale, and sandstone related to the Mid-Continent Rift zone. | High | 12 | 27.5% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Clay County beside the ground around it
On high-potential ground Clay County is close to Kansas as a whole: 65.3% of its land against 59.9%. Every one of the 6 counties that border it has more high-potential ground, Cloud County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Clay County, Local resources
Radon testing and mitigation in Clay County
Listed radon businesses with an address in Clay County:
- Kansas Radon ProgramKansas Radon Program answers questions about testing, mitigation and the rules in Kansas.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Kansas178 professionals are listed in Kansas.
Listed radon professionals by town: Clay Center
What Kansas's program says
- Phone
- (800) 693-5343
What it means
Clay County, Questions
Questions about radon in Clay County
Are radon levels high in Clay County?
In 2022, 55.8% of the radon tests reported to CDC for Clay County, Kansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.8 pCi/L. Of 38 Kansas counties with 30 or more tests for the same period, 1 reported a higher share; pooled, the state comes to 32.0%.
Which counties border Clay County?
Clay County borders 6 counties: Riley County, Cloud County, Washington County, Ottawa County, Geary County and Dickinson County.
Products
Clay County, Products
Testing a home in Clay County
In Clay County, 55.8% of 77 tests reported to CDC in 2022 reached 4 pCi/L, against 32.0% pooled across Kansas. In Zone 1 the year-round level in Clay 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
Monitor
RadonPro Wi-Fi radon monitor with a built-in Geiger counter
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Clay County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Clay County
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Clay County, Bordering counties
Counties bordering Clay County
Calculated by Radon411- Radon levels in Cloud CountyEPA zone 1
54.6%at or above 4 pCi/L
Median 4.3 pCi/L · 97 tests · 1.2 points below Clay County
- Radon levels in Washington CountyEPA zone 1
43.8%at or above 4 pCi/L
Median 3.3 pCi/L · 16 tests · 12.0 points below Clay County
- Radon levels in Dickinson CountyEPA zone 1
38.9%at or above 4 pCi/L
Median 2.7 pCi/L · 113 tests · 16.9 points below Clay County
- Radon levels in Ottawa CountyEPA zone 1
32.0%at or above 4 pCi/L
Median 3.3 pCi/L · 25 tests · 23.8 points below Clay County
- Radon levels in Riley CountyEPA zone 1
31.3%at or above 4 pCi/L
Median 1.9 pCi/L · 800 tests · 24.5 points below Clay County
- Radon levels in Geary CountyEPA zone 1
25.2%at or above 4 pCi/L
Median 1.9 pCi/L · 365 tests · 30.6 points below Clay County
Clay County, Cities and towns
Cities and towns in Clay County
About 7,990 people live in Clay County by the Census Bureau's estimate for July 1, 2025, 136 fewer than in 2020 (−1.7%). That works out to 12 people per square mile of land. Clay Center alone is home to 4,061 of them, 50.8% of the total. Testing is reported here more often than across the state: CDC's 77 reported tests for 2022 come to 9.6 for every 1,000 residents (2025 estimate), against 6.2 for Kansas.
From Clay Center to Oak Hill, CDC publishes no figure by town: each reads Clay County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Clay Center | 4,061 | −3.2% | 50.8% |
| Wakefield | 835 | −3.5% | 10.5% |
| Cliftonextends beyond Clay County | 457 | +1.1% | Counted whole |
| Morganville | 181 | +0.6% | 2.3% |
| Green | 92 | −5.2% | 1.2% |
| Longford | 71 | −2.7% | 0.9% |
| Viningextends beyond Clay County | 43 | +2.4% | Counted whole |
| Oak Hill | 24 | Level | 0.3% |
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). A place that extends beyond Clay County is counted whole, so it has no share.
Clay County, Homes
Homes in Clay County
Clay County is a place of houses on their own lots: 85% of its 3,940 homes are detached single-family houses, against 72% across Kansas. The homes are older than Kansas' as a whole: half were built before 1961 (1975 for Kansas), and 49% date from before 1960. 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 | Clay County | Kansas |
|---|---|---|
| Housing units | 3,940 | 1,285,221 |
| Detached houses | 85% | 72% |
| In buildings of 5 or more | 5% | 13% |
| Mobile homes | 3% | 4% |
| Built before 1960 | 49% | 33% |
| Built since 2000 | 11% | 20% |
| Middle year built | 1961 | 1975 |
| Owner-occupied | 73% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.