Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Warren County, Missouri
EPA puts Warren County in Zone 2, its middle radon zone, and only 7 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
36.8%
6.2 pts above MO
- Warren
- 36.8%
- Missouri
- 30.6%
285 tests, 2008 to 2017
Median result
2.7pCi/L
Below action level
- Warren
- 2.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
285
17th of 72 by tests
- Warren
- 285
- 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
26 of 72
Middle half
- Warren
- 36.8%
- Atchison
- 69.9%
By share, of 72 with 30+ tests
Read a result for Warren County
Starts at Warren County's median, 2.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.7 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. Warren County's median reported result, 2008 to 2017.
The data
Warren County, At a glance
Warren County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Warren 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 Warren County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 53.3% |
| 2015 | 8.3% |
| 2016 | 69.6% |
| 2017 | 50.0% |
| 2018 | 87.5% |
| 2019 | 0.0% |
| 2020 | 75.0% |
| 2021 | 55.6% |
| 2022 | 28.6% |
| 2023 | 57.1% |
2023: 57.1%. Across these years the share ran from 0.0% to 87.5%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 7 tests were reported to CDC for Warren 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).
Warren County, Compared
Warren County radon figures, compared
Calculated by Radon411In Warren County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (105 of 285) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 1.1 points higher. Across 115 Missouri counties pooled together, 30.6% of tests reached that level, so Warren County runs 6.2 points above its state.
The newest figure, in 2023, counts only 7 tests (57.1% at or above 4 pCi/L), too few to compare, so this reading uses the 285-test figure.
Of 5 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 12.8% (Montgomery County) to 33.6% (Lincoln County). By share, Warren County is 26th of 72 Missouri counties with 30 or more tests for the same period.
Half the tests came in under 2.7 pCi/L and half over it; the single highest reached 70.8 pCi/L. Below the action level, 121 tests (42.5%) came in under 2 pCi/L, against 41.2% statewide, and 59 tests (20.7%) 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 36.8% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential. CDC also counts 9 tests taken after mitigation in Warren County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2016, with 23 tests reported; the quietest, 2019, had 1.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Warren County, Geology
The ground under Warren County
PredictedUSGS's geologic map puts all of Warren County's mapped land in one class: moderate radon potential. The map puts 86.0% of Warren County in the area it calls Salem Plateau and 14.0% in Dissected Till Plains. 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 |
|---|---|---|---|---|
| Salem Plateau | Ordovician dolomite, sandstone, limestone, and shale. | Moderate | 11 | 86.0% |
| Dissected Till Plains | Till-covered Pennsylvanian sandstone, shale, and limestone. | Moderate | 11 | 14.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Warren County beside the ground around it
Across Missouri 8.2% of the land is rated high; none of Warren County's is. Of the 5 counties that border it, 1 has more high-potential ground, Lincoln County the most at 2.6%.
The map rates the ground, not the air in any home.
Local help
Warren County, Local resources
Radon testing and mitigation in Warren 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
Warren County, Questions
Questions about radon in Warren County
Are radon levels high in Warren County?
In 2023, 57.1% of the radon tests reported to CDC for Warren County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.7 pCi/L. Of 72 Missouri counties with 30 or more tests for the same period, 25 reported a higher share; pooled, the state comes to 30.6%.
Which counties border Warren County?
Warren County borders 5 counties: Montgomery County, Lincoln County, Franklin County, St. Charles County and Gasconade County.
Products
Warren County, Products
Testing a home in Warren County
In Warren County, 36.8% of 285 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 Warren County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Monitor
lüft plug-in radon and indoor air quality monitor
- C-NRPP 2024/25: Approved
- Plug-in
- Wi-Fi, Bluetooth
- App only
First reading: Within 90 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Warren County, Bordering counties
Counties bordering Warren County
Calculated by Radon411- Radon levels in Lincoln CountyEPA zone 2
33.6%at or above 4 pCi/L
Median 2.2 pCi/L · 444 tests · 3.2 points below Warren County
- Radon levels in Franklin CountyEPA zone 2
33.2%at or above 4 pCi/L
Median 2.6 pCi/L · 753 tests · 3.6 points below Warren County
- Radon levels in Gasconade CountyEPA zone 2
31.8%at or above 4 pCi/L
Median 2.3 pCi/L · 44 tests · 5.0 points below Warren County
- Radon levels in St. Charles CountyEPA zone 2
26.5%at or above 4 pCi/L
Median 2.2 pCi/L · 7,001 tests · 10.3 points below Warren County
- Radon levels in Montgomery CountyEPA zone 2
12.8%at or above 4 pCi/L
Median 1.6 pCi/L · 47 tests · 24.0 points below Warren County
Warren County, Cities and towns
Cities and towns in Warren County
Warren County is growing: the Census Bureau puts it at 39,016 residents on July 1, 2025, up 9.2% from 35,740 in 2020. That works out to 91 people per square mile of land. Its largest town, Warrenton, has 9,667 residents, 24.8% of the total. CDC's 285 reported tests for 2008 to 2017 work out to 7.3 per 1,000 residents (2025 estimate), close to Missouri's 9.3.
From Warrenton to Three Creeks, CDC publishes no figure by town: each reads Warren County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Warrenton | 9,667 | +13.2% | 24.8% |
| Wright City | 5,854 | +20.3% | 15.0% |
| Marthasville | 1,302 | +2.9% | 3.3% |
| Truesdale | 1,054 | +21.4% | 2.7% |
| Foristellextends beyond Warren County | 919 | +68.3% | Counted whole |
| Innsbrook | 653 | +9.7% | 1.7% |
| Pendleton | 30 | +3.4% | Under 0.1% |
| Three Creeks | 6 | Level | Under 0.1% |
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 Warren County is counted whole, so it has no share.
Warren County, Homes
Homes in Warren County
Warren County is a place of houses on their own lots: 79% of its 15,834 homes are detached single-family houses, against 70% across Missouri. Much of Warren County is recent building: 43% of its homes have gone up since 2000 and the middle year built is 1996, against 1978 for Missouri. Owners live in 82% of the occupied homes (Missouri: 68%), so for most households a test and a fix are their own to order.
| Homes | Warren County | Missouri |
|---|---|---|
| Housing units | 15,834 | 2,809,501 |
| Detached houses | 79% | 70% |
| In buildings of 5 or more | 3% | 13% |
| Mobile homes | 10% | 5% |
| Built before 1960 | 8% | 28% |
| Built since 2000 | 43% | 21% |
| Middle year built | 1996 | 1978 |
| Owner-occupied | 82% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.