Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
Locations and reports
Radon Levels in Henry County, Missouri
EPA puts Henry County in Zone 2, its middle radon zone, and only 4 radon tests from it are on file with CDC (2023). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
38.3%
7.7 pts above MO
- Henry
- 38.3%
- Missouri
- 30.6%
81 tests, 2008 to 2017
Median result
3.4pCi/L
Below action level
- Henry
- 3.4 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
81
44th of 72 by tests
- Henry
- 81
- St. Louis
- 17,747
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in Missouri
19 of 72
Middle half
- Henry
- 38.3%
- Atchison
- 69.9%
By share, of 72 with 30+ tests
Read a result for Henry County
Starts at Henry County's median, 3.4 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.4 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 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. Henry County's median reported result, 2008 to 2017.
The data
Henry County, At a glance
Henry County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Henry County is a
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 Henry County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 28.6% |
| 2015 | 33.3% |
| 2016 | 11.1% |
| 2017 | 100.0% |
| 2018 | 0.0% |
| 2019 | 0.0% |
| 2020 | 16.7% |
| 2021 | 0.0% |
| 2022 | 50.0% |
| 2023 | 50.0% |
2023: 50.0%. Across these years the share ran from 0.0% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 4 tests were reported to CDC for Henry County over 2023, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Henry County, Compared
Henry County radon figures, compared
Calculated by Radon411In Henry County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (31 of 81) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 2.6 points higher. Across 115 Missouri counties pooled together, 30.6% of tests reached that level, so Henry County runs 7.7 points above its state.
The newest figure, in 2023, counts only 4 tests (50.0% at or above 4 pCi/L), too few to compare, so this reading uses the 81-test figure.
Of 4 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 25.8% (Johnson County) to 45.5% (Cass County). By share, Henry County is 19th of 72 Missouri counties with 30 or more tests for the same period.
Half the tests came in under 3.4 pCi/L and half over it; the single highest reached 71.0 pCi/L. Below the action level, 26 tests (32.1%) came in under 2 pCi/L, against 41.2% statewide, and 24 tests (29.6%) fell between 2 and 4, against 28.1% statewide.
Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 38.3% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential.
The busiest year on file was 2022, with 12 tests reported; the quietest, 2019, had 1.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Henry County, Geology
The ground under Henry County
PredictedUSGS's geologic map puts all of Henry County's mapped land in one class: moderate radon potential. The map puts 89.8% of Henry County in the area it calls Osage Plains and 10.2% in Springfield Plateau. USGS gives both a radon index of 11, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Osage Plains | Ordovician dolomite, sandstone, limestone, and shale. | Moderate | 11 | 89.8% |
| Springfield Plateau | Mississippian limestone, shale, and sandstone. | Moderate | 11 | 10.2% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Henry County beside the ground around it
Across Missouri 8.2% of the land is rated high; none of Henry County's is. Of the 6 counties that border it, 2 have more high-potential ground, Cass County the most at 35.5%.
The map rates the ground, not the air in any home.
Local help
Henry County, Local resources
Radon testing and mitigation in Henry County
- Missouri Radon ProgramMissouri Radon Program, run by Missouri Department of Health and Senior Services, offers free or discounted test kits, and answers questions about testing and mitigation in Missouri.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Free radon test kits are available for Missouri residents (limit one per household).
- Compare kits
- Professionals in Missouri27 professionals are listed in Missouri.
What Missouri's program says
- Phone
- 573-751-6102
- radon@health.mo.gov
What it means
Henry County, Questions
Questions about radon in Henry County
Are radon levels high in Henry County?
In 2023, 50.0% of the radon tests reported to CDC for Henry County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.5 pCi/L. Of 72 Missouri counties with 30 or more tests for the same period, 18 reported a higher share; pooled, the state comes to 30.6%.
Which counties border Henry County?
Henry County borders 6 counties: St. Clair County, Benton County, Bates County, Johnson County, Cass County and Pettis County.
Products
Henry County, Products
Testing a home in Henry County
In Henry County, 38.3% of 81 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 30.6% pooled across Missouri. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Henry County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
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
MonitorX-Sense
XR0A-SR battery digital radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Henry County, Bordering counties
Counties bordering Henry County
Calculated by Radon411- Radon levels in Cass CountyEPA zone 1
45.5%at or above 4 pCi/L
Median 3.5 pCi/L · 988 tests · 7.2 points above Henry County
- Radon levels in Pettis CountyEPA zone 2
37.9%at or above 4 pCi/L
Median 2.8 pCi/L · 132 tests · 0.4 points below Henry County
- Radon levels in Benton CountyEPA zone 2
30.6%at or above 4 pCi/L
Median 2.0 pCi/L · 49 tests · 7.7 points below Henry County
- Radon levels in Bates CountyEPA zone 2
26.1%at or above 4 pCi/L
Median 1.5 pCi/L · 23 tests · 12.2 points below Henry County
- Radon levels in Johnson CountyEPA zone 2
25.8%at or above 4 pCi/L
Median 1.9 pCi/L · 264 tests · 12.5 points below Henry County
- Radon levels in St. Clair CountyEPA zone 2
7.7%at or above 4 pCi/L
Median 1.5 pCi/L · 13 tests · 30.6 points below Henry County
Henry County, Cities and towns
Cities and towns in Henry County
The Census Bureau estimates 22,671 residents in Henry County for July 1, 2025, 695 more than in 2020 (+3.2%). That works out to 33 people per square mile of land. Its largest town, Clinton, has 9,504 residents, 41.9% of the total. Reported testing is thin here: 81 tests over 2008 to 2017, or 3.6 for every 1,000 residents (2025 estimate), where Missouri as a whole comes to 9.3.
From Clinton to Tightwad, CDC publishes no figure by town: each reads Henry County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Clinton | 9,504 | +3.2% | 41.9% |
| Windsorextends beyond Henry County | 2,869 | +3.5% | Counted whole |
| Urich | 478 | +1.7% | 2.1% |
| Calhoun | 406 | +2.5% | 1.8% |
| Montrose | 392 | +2.1% | 1.7% |
| Deepwater | 382 | +7.0% | 1.7% |
| Blairstown | 98 | +3.2% | 0.4% |
| Brownington | 70 | +2.9% | 0.3% |
| Tightwad | 58 | +3.6% | 0.3% |
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). A place that extends beyond Henry County is counted whole, so it has no share.
Henry County, Homes
Homes in Henry County
Of Henry County's 10,708 homes, 74% are detached houses, against 70% across Missouri; 12% are mobile homes. Half of its homes were built before 1979, close to Missouri's 1978: 27% date from before 1960 and 20% from 2000 or later. 74% of occupied homes are lived in by their owner (Missouri: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Henry County | Missouri |
|---|---|---|
| Housing units | 10,708 | 2,809,501 |
| Detached houses | 74% | 70% |
| In buildings of 5 or more | 4% | 13% |
| Mobile homes | 12% | 5% |
| Built before 1960 | 27% | 28% |
| Built since 2000 | 20% | 21% |
| Middle year built | 1979 | 1978 |
| Owner-occupied | 74% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.