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 St. Francois County, Missouri
EPA puts St. Francois County in Zone 2, its middle radon zone, and only 1 radon test from it is 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
41.1%
10.5 pts above MO
- St. Francois
- 41.1%
- Missouri
- 30.6%
146 tests, 2008 to 2017
Median result
2.9pCi/L
Below action level
- St. Francois
- 2.9 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
146
29th of 72 by tests
- St. Francois
- 146
- 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
15 of 72
Top quarter
- St. Francois
- 41.1%
- Atchison
- 69.9%
By share, of 72 with 30+ tests
Read a result for St. Francois County
Starts at St. Francois County's median, 2.9 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.9 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. St. Francois County's median reported result, 2008 to 2017.
The data
St. Francois County, At a glance
St. Francois County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
St. Francois County is a
USGS geologic potential: Moderate across 69% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for St. Francois County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 16.7% |
| 2015 | 23.1% |
| 2016 | 34.1% |
| 2017 | 33.3% |
| 2018 | 28.6% |
| 2019 | 50.0% |
| 2020 | 75.0% |
| 2021 | 50.0% |
| 2022 | 66.7% |
| 2023 | 0.0% |
2023: 0.0%. Across these years the share ran from 0.0% to 75.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 1 test was reported to CDC for St. Francois 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).
St. Francois County, Compared
St. Francois County radon figures, compared
Calculated by Radon411In St. Francois County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (60 of 146) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 5.4 points higher. Across 115 Missouri counties pooled together, 30.6% of tests reached that level, so St. Francois County runs 10.5 points above its state.
The newest figure, in 2023, counts only 1 test (0.0% at or above 4 pCi/L), too few to compare, so this reading uses the 146-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 26.3% (Washington County) to 41.6% (Jefferson County). By share, St. Francois County is 15th of 72 Missouri counties with 30 or more tests for the same period.
Half the tests came in under 2.9 pCi/L and half over it; the single highest reached 33.0 pCi/L. Below the action level, 54 tests (37.0%) came in under 2 pCi/L, against 41.2% statewide, and 32 tests (21.9%) 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 41.1% share point the same way here. USGS geology rates 69% of the county's land moderate radon potential. CDC also counts 6 tests taken after mitigation in St. Francois County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2016, with 41 tests reported; the quietest, 2023, had 1.
Pooled shares: Radon411's sum of CDC's county counts for one period.
St. Francois County, Geology
The ground under St. Francois County
PredictedUSGS's geologic map splits St. Francois County: 68.8% of its land is moderate radon potential and 31.2% high. The map puts 68.8% of St. Francois County in the area it calls Salem Plateau and 31.2% in St. Francois Mountains. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Salem Plateau | Ordovician dolomite, sandstone, limestone, and shale. | Moderate | 11 | 68.8% |
| St. Francois Mountains | Granitic and volcanic rocks. Some soils have high uranium concentrations. | High | 13 | 31.2% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
St. Francois County beside the ground around it
St. Francois County has more high-potential ground than Missouri as a whole: 31.2% of its land against 8.2%. Of the 6 counties that border it, 2 have more high-potential ground, Iron County the most at 85.3%.
The map rates the ground, not the air in any home.
Local help
St. Francois County, Local resources
Radon testing and mitigation in St. Francois 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
St. Francois County, Questions
Questions about radon in St. Francois County
Are radon levels high in St. Francois County?
In 2023, 0.0% of the radon tests reported to CDC for St. Francois County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.8 pCi/L. Of 72 Missouri counties with 30 or more tests for the same period, 14 reported a higher share; pooled, the state comes to 30.6%.
Which counties border St. Francois County?
St. Francois County borders 6 counties: Ste. Genevieve County, Washington County, Iron County, Madison County, Jefferson County and Perry County.
Products
St. Francois County, Products
Testing a home in St. Francois County
In St. Francois County, 41.1% of 146 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 St. Francois 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
Monitor
RadonScan-Plus USB-powered radon monitor with Wi-Fi
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
St. Francois County, Bordering counties
Counties bordering St. Francois County
Calculated by Radon411- Radon levels in Iron CountyEPA zone 1
50.0%at or above 4 pCi/L
Median 3.5 pCi/L · 14 tests · 8.9 points above St. Francois County
- Radon levels in Jefferson CountyEPA zone 2
41.6%at or above 4 pCi/L
Median 3.1 pCi/L · 2,652 tests · 0.5 points above St. Francois County
- Radon levels in Madison CountyEPA zone 2
39.1%at or above 4 pCi/L
Median 3.5 pCi/L · 23 tests · 2.0 points below St. Francois County
- Radon levels in Perry CountyEPA zone 2
37.8%at or above 4 pCi/L
Median 3.2 pCi/L · 82 tests · 3.3 points below St. Francois County
- Radon levels in Ste. Genevieve CountyEPA zone 2
31.1%at or above 4 pCi/L
Median 2.5 pCi/L · 74 tests · 10.0 points below St. Francois County
- Radon levels in Washington CountyEPA zone 2
26.3%at or above 4 pCi/L
Median 1.5 pCi/L · 38 tests · 14.8 points below St. Francois County
St. Francois County, Cities and towns
Cities and towns in St. Francois County
The Census Bureau estimates 67,809 residents in St. Francois County for July 1, 2025, 1,376 more than in 2020 (+2.1%). That works out to 150 people per square mile of land. Its largest town, Farmington, has 19,226 residents, 28.4% of the total. Together its 8 incorporated places hold 63.8% of those residents; the other 36.2% live outside any of them. Reported testing is thin here: 146 tests over 2008 to 2017, or 2.2 for every 1,000 residents (2025 estimate), where Missouri as a whole comes to 9.3.
From Farmington to Iron Mountain Lake, CDC publishes no figure by town: each reads St. Francois County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Farmington | 19,226 | +8.4% | 28.4% |
| Park Hills | 8,753 | +1.7% | 12.9% |
| Bonne Terre | 6,636 | −3.3% | 9.8% |
| Desloge | 4,819 | −0.1% | 7.1% |
| Bismarck | 1,224 | −0.7% | 1.8% |
| Leadwood | 1,158 | −1.4% | 1.7% |
| Leadington | 785 | +2.3% | 1.2% |
| Iron Mountain Lake | 647 | +0.9% | 1.0% |
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).
St. Francois County, Homes
Homes in St. Francois County
Of St. Francois County's 28,815 homes, 67% are detached houses, against 70% across Missouri; 12% are mobile homes. Half of its homes were built before 1981, close to Missouri's 1978: 26% date from before 1960 and 24% from 2000 or later. 69% 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 | St. Francois County | Missouri |
|---|---|---|
| Housing units | 28,815 | 2,809,501 |
| Detached houses | 67% | 70% |
| In buildings of 5 or more | 10% | 13% |
| Mobile homes | 12% | 5% |
| Built before 1960 | 26% | 28% |
| Built since 2000 | 24% | 21% |
| Middle year built | 1981 | 1978 |
| Owner-occupied | 69% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.