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 Stark County, Illinois
EPA puts Stark County in Zone 1, its highest radon zone, and high results are common there: 69.2% of the 39 radon tests reported to CDC (2017) 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
69.2%
35.5 pts above IL
- Stark
- 69.2%
- Illinois
- 33.7%
39 tests, 2017
Median result
5.8pCi/L
Action level reached
- Stark
- 5.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2017
Tests reported
39
67th of 70 by tests
- Stark
- 39
- Cook
- 26,937
Reported to CDC before any fix, 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Illinois
1 of 70
Top quarter
- Stark
- 69.2%
- Stark
- 69.2%
By share, of 70 with 30+ tests
Read a result for Stark County
Starts at Stark County's median, 5.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 5.8 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. Stark County's median reported result, 2017.
The data
Stark County, At a glance
Stark County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Stark County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Stark County, 2017
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 80.0% |
| 2015 | 66.7% |
| 2017 | 69.2% |
2017: 69.2%. Across these years the share ran from 66.7% to 80.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 39 tests reported to CDC for Stark County over 2017, 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: 2017. Measured data period: 2005 to 2017 (every CDC figure on file).
Stark County, Compared
Stark County radon figures, compared
Calculated by Radon411More than half: 69.2% of the 39 radon tests reported to CDC for Stark County in 2017 read at least 4 pCi/L. That places it 1st of 70 Illinois counties with 30 or more tests for the same period. That is 35.5 points above the 33.7% pooled from 93 Illinois counties.
The median result, 5.8 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 73.8 pCi/L. The rest split 15.4% under 2 pCi/L and 15.4% from 2 to 4 (Illinois: 37.7% and 28.6%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 69.2% share point the same way here.
No bordering county with a figure for the same period reported a higher share; the closest is Bureau County at 58.6%, the lowest Peoria County at 40.2%. Statewide for the same period, Mercer County reported the highest share (68.2%) and Williamson County the lowest (8.4%).
The busiest year on file was 2017, with 39 tests reported; the quietest, 2015, had 9.
Nationally, every county with a figure for the same period pools to 31.7%; Stark County sits 37.5 points above it.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Stark County, Geology
The ground under Stark County
PredictedUSGS's geologic map puts all of Stark County's mapped land in one class: high radon potential. The map puts 84.6% of Stark County in the area it calls Galesburg Plain and 15.4% in Bloomington Ridged Plain. USGS gives both a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Galesburg Plain | Illinoian glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 84.6% |
| Bloomington Ridged Plain | Wisconsinan glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 15.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Stark County beside the ground around it
Stark County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 5 counties that border it, none has as large a share of high-potential ground; Henry County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Stark County, Local resources
Radon testing and mitigation in Stark County
- IEMA-OHS Radon ProgramIEMA-OHS Radon Program, run by Illinois Emergency Management Agency and Office of Homeland Security, licenses or certifies radon professionals and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in Illinois.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 Illinois339 professionals are listed in Illinois.
What Illinois's program says
- Phone
- (800) 325-1245
- Licensing of radon professionals
The Agency also licenses and regulates the individuals who provide radon measurement and mitigation to the public.
- Disclosure when a home is sold or rented
Illinois Radon Awareness Act - This is the legislation that requires the seller to provide to the buyer of any interest in residential real property the IEMA-OHS pamphlet entitled "Radon Testing Guidelines for Real Estate Transactions" and the Illinois Disclosure of Information on Radon Hazards.
What it means
Stark County, Questions
Questions about radon in Stark County
Are radon levels high in Stark County?
In 2017, 69.2% of the radon tests reported to CDC for Stark County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.8 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 33.7%.
Which counties border Stark County?
Stark County borders 5 counties: Peoria County, Marshall County, Knox County, Henry County and Bureau County.
Products
Stark County, Products
Testing a home in Stark County
In Stark County, 69.2% of 39 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Stark 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
EcoQube Wi-Fi continuous radon monitor
- C-NRPP 2024/25: Approved
- Plug-in
- Wi-Fi
- App only
Method: Ion chamber
First reading: Within 10 minutes
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Stark County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Stark County
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Stark County, Bordering counties
Counties bordering Stark County
Calculated by Radon411- Radon levels in Bureau CountyEPA zone 1
58.6%at or above 4 pCi/L
Median 5.1 pCi/L · 333 tests · 10.6 points below Stark County
- Radon levels in Knox CountyEPA zone 1
56.6%at or above 4 pCi/L
Median 4.7 pCi/L · 249 tests · 12.6 points below Stark County
- Radon levels in Henry CountyEPA zone 1
55.7%at or above 4 pCi/L
Median 4.6 pCi/L · 420 tests · 13.5 points below Stark County
- Radon levels in Marshall CountyEPA zone 1
48.1%at or above 4 pCi/L
Median 3.8 pCi/L · 81 tests · 21.1 points below Stark County
- Radon levels in Peoria CountyEPA zone 1
40.2%at or above 4 pCi/L
Median 3.1 pCi/L · 3,816 tests · 29.0 points below Stark County
Stark County, Cities and towns
Cities and towns in Stark County
About 5,319 people live in Stark County by the Census Bureau's estimate for July 1, 2025, 63 fewer than in 2020 (−1.2%). That works out to 18 people per square mile of land. Its largest town, Wyoming, has 1,287 residents, 24.2% of the total. Together its 4 incorporated places hold 61.7% of those residents; the other 38.3% live outside any of them. CDC's 39 reported tests for 2017 work out to 7.3 per 1,000 residents (2025 estimate), close to Illinois' 10.9.
From Wyoming to La Fayette, CDC publishes no figure by town: each reads Stark County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Wyoming | 1,287 | −0.7% | 24.2% |
| Toulon | 1,172 | −1.0% | 22.0% |
| Bradford | 666 | −1.6% | 12.5% |
| La Fayette | 157 | −1.3% | 3.0% |
4 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).
Stark County, Homes
Homes in Stark County
Stark County is a place of houses on their own lots: 86% of its 2,584 homes are detached single-family houses, against 58% across Illinois. The homes are older than Illinois' as a whole: half were built before 1956 (1970 for Illinois), and 55% date from before 1960. Owners live in 78% of the occupied homes (Illinois: 67%), so for most households a test and a fix are their own to order.
| Homes | Stark County | Illinois |
|---|---|---|
| Housing units | 2,584 | 5,443,501 |
| Detached houses | 86% | 58% |
| In buildings of 5 or more | 3% | 22% |
| Mobile homes | 3% | 2% |
| Built before 1960 | 55% | 38% |
| Built since 2000 | 6% | 16% |
| Middle year built | 1956 | 1970 |
| Owner-occupied | 78% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.