Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Knox County, Missouri
EPA puts Knox 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
Highest bordering
32.4%
Lewis County
- Lewis
- 32.4%
- Macon
- 19.4%
3 of 6 neighbours have 30+ tests, 2008 to 2017
Nearest county
32.4%
Lewis County, 23 miles
- Lewis
- 32.4%
- Missouri
- 30.6%
Share at 4+ pCi/L, 71 tests, 2008 to 2017
Ground above low
100.0%
5.8 pts above Missouri
- Knox
- 100.0%
- Missouri
- 94.2%
Share of land USGS rates moderate or high potential
Tests reported
10
Too few for a share
- Knox
- 10
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Read a result for Knox County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 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.
The data
Knox County, At a glance
Knox County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Knox 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 Knox County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 0.0% |
| 2015 | 0.0% |
| 2016 | 0.0% |
| 2021 | 100.0% |
| 2023 | 0.0% |
2023: 0.0%. 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 1 test was reported to CDC for Knox 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).
Knox County, Compared
Knox County radon figures, compared
Calculated by Radon411CDC's largest figure for Knox County rests on 10 tests over the 2008 to 2017 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 10.0 points and no rank or comparison is drawn from it. Results reached as high as 3.2 pCi/L, with a middle value of 1.9 pCi/L.
Of the counties bordering it, 3 have a figure over the 2008 to 2017 laboratory totals: Lewis County reported the largest share at or above 4 pCi/L, 32.4%, and Macon County the smallest, 19.4%, with Adair County at 27.2% between. Farther out, Marion County (36 miles away) at 41.8%, Monroe County (44 miles away) at 23.3% and Randolph County (51 miles away) at 17.2% have figures too. Pooled across 115 Missouri counties, 30.6% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Atchison County reported the highest share (69.9%) and Vernon County the lowest (8.8%). EPA's 1993 map puts Knox County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Knox County, Geology
The ground under Knox County
PredictedUSGS's geologic map puts all of Knox County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Dissected Till Plains, to which USGS gives 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 |
|---|---|---|---|---|
| Dissected Till Plains | Till-covered Pennsylvanian sandstone, shale, and limestone. | Moderate | 11 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Knox County beside the ground around it
Across Missouri 8.2% of the land is rated high; none of Knox County's is. Of the 6 counties that border it, 2 have more high-potential ground, Lewis County the most at 9.1%.
The map rates the ground, not the air in any home.
Local help
Knox County, Local resources
Radon testing and mitigation in Knox 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
Knox County, Questions
Questions about radon in Knox County
Are radon levels high in Knox County?
In 2023, 0.0% of the radon tests reported to CDC for Knox County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.4 pCi/L. Of the counties bordering it, 3 have a figure over the 2008 to 2017 laboratory totals: Lewis County reported the largest share at or above 4 pCi/L, 32.4%, and Macon County the smallest, 19.4%, with Adair County at 27.2% between.
Which counties border Knox County?
Knox County borders 6 counties: Scotland County, Lewis County, Shelby County, Adair County, Clark County and Macon County.
Products
Knox County, Products
Testing a home in Knox County
No CDC figure names Knox County; the nearest county with one, Lewis County (23 miles away), reported 32.4% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Knox 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
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
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Knox County, Bordering counties
Counties bordering Knox County
Calculated by Radon411- Radon levels in Lewis CountyEPA zone 2
32.4%at or above 4 pCi/L
Median 2.6 pCi/L · 71 tests
- Radon levels in Clark CountyEPA zone 2
29.4%at or above 4 pCi/L
Median 2.2 pCi/L · 17 tests
- Radon levels in Adair CountyEPA zone 2
27.2%at or above 4 pCi/L
Median 1.8 pCi/L · 92 tests
- Radon levels in Shelby CountyEPA zone 2
24.1%at or above 4 pCi/L
Median 1.7 pCi/L · 29 tests
- Radon levels in Macon CountyEPA zone 2
19.4%at or above 4 pCi/L
Median 1.7 pCi/L · 36 tests
- Radon levels in Scotland CountyEPA zone 2
16.7%at or above 4 pCi/L
Median 1.4 pCi/L · 18 tests
Knox County, Cities and towns
Cities and towns in Knox County
Knox County's population has barely moved since 2020: 3,728 residents on July 1, 2025 against 3,733 then, by the Census Bureau's estimates. Spread over its land, that is 7.4 people to the square mile. Its largest town, Edina, has 1,014 residents, 27.2% of the total. Together its 6 incorporated places hold 44.1% of those residents; the other 55.9% live outside any of them. Reported testing is thin here: 10 tests over 2008 to 2017, or 2.7 for every 1,000 residents (2025 estimate), where Missouri as a whole comes to 9.3.
From Edina to Newark, CDC publishes no figure by town: each reads Knox County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Edina | 1,014 | +1.4% | 27.2% |
| Knox City | 186 | −1.6% | 5.0% |
| Hurdland | 153 | −1.9% | 4.1% |
| Baring | 121 | −0.8% | 3.2% |
| Novelty | 113 | −2.6% | 3.0% |
| Newark | 58 | Level | 1.6% |
6 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).
Knox County, Homes
Homes in Knox County
Knox County is a place of houses on their own lots: 83% of its 1,940 homes are detached single-family houses, against 70% across Missouri. The homes are older than Missouri's as a whole: half were built before 1964 (1978 for Missouri), and 45% date from before 1960. Owners live in 86% of the occupied homes (Missouri: 68%), so for most households a test and a fix are their own to order.
| Homes | Knox County | Missouri |
|---|---|---|
| Housing units | 1,940 | 2,809,501 |
| Detached houses | 83% | 70% |
| In buildings of 5 or more | 2% | 13% |
| Mobile homes | 10% | 5% |
| Built before 1960 | 45% | 28% |
| Built since 2000 | 12% | 21% |
| Middle year built | 1964 | 1978 |
| Owner-occupied | 86% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.