Locations and reports
Radon in St. Charles, Illinois
St. Charles lies in 2 counties, in EPA Zones 1 and 2; 97.2% of it is in Kane County, where 36.6% of 8,682 reported tests (2017) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so the only way to know your home's level is to test it.
Data checked By Radon411Methodology
Share at 4+ pCi/L
36.6%
2.9 pts above IL
- Kane
- 36.6%
- Illinois
- 33.7%
Kane, 47th of 70 in IL, 2017
Median result
2.8pCi/L
Below action level
- Kane
- 2.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of Kane's tests, 2017
Highest county
36.6%
Kane
- Kane
- 36.6%
- DuPage
- 33.7%
2 counties, 2 with 30+ tests, 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
Kane; DuPage Zone 2
Tests reported
8,682
In Kane
- Kane
- 8,682
- DuPage
- 19,401
Reported to CDC before any fix, 2017
Read a result for St. Charles
Starts at Kane County's median, 2.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.8 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. Kane County's median reported result, 2017.
The data
St. Charles, What is published
What is published for St. Charles
Every figure for St. Charles is a county's
Radon data is published by county, not by city, and St. Charles reaches into 2 counties: Kane County and DuPage County. Each has its own EPA zone and its own CDC test figures, set side by side below and each labelled with its county. Only a test tells you about one home.
St. Charles covers 14.4 square miles of land: 97.2% of it lies in Kane County and 2.8% in DuPage County. About 33,594 people live there, 2,333 to the square mile.
St. Charles, Counties
St. Charles's counties, side by side
MeasuredEach county's own EPA zone and its own published CDC figures for 2017, the newest period any of them has. A county without a figure for that period is shown without one, never with a figure from another year.
- Kane County
- EPA zone
- Zone 1: Highest predicted potential
- At or above 4 pCi/L
- 36.6%
- Median result
- 2.8 pCi/L
- Tests reported
- 8,682 tests
- Annual years on file
- 4
- DuPage County
- EPA zone
- Zone 2: Moderate predicted potential
- At or above 4 pCi/L
- 33.7%
- Median result
- 2.7 pCi/L
- Tests reported
- 19,401 tests
- Annual years on file
- 4
| County | EPA zone | Reported tests at or above 4 pCi/L | Median reported result | Tests reported | Annual years on file |
|---|---|---|---|---|---|
| Kane County | Zone 1: Highest predicted potential | 36.6% | 2.8 pCi/L | 8,682 tests | 4 |
| DuPage County | Zone 2: Moderate predicted potential | 33.7% | 2.7 pCi/L | 19,401 tests | 4 |
St. Charles spans 2 counties, each with its own EPA zone and its own CDC figure: Kane County (Zone 1, 36.6% of 8,682 tests) and DuPage County (Zone 2, 33.7% of 19,401 tests).
Kane County ranks 47th of 70 Illinois counties with 30 or more tests for that period, 2.9 points above the 33.7% pooled across Illinois's counties, 4.9 points above the national pool of 31.7%. Of the city's other county, DuPage County reported 33.7%.
Measured from the middle of St. Charles, the nearest counties with a CDC figure for 2017 are Kendall County (23 miles, 35.0% of 3,045 tests), DeKalb County (24 miles, 41.1% of 1,707 tests) and Cook County (26 miles, 19.4% of 26,937 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 19.4% to 46.9%; the farthest of them, Grundy County, is 44 miles away at 32.3%.
No business in the directory gives St. Charles as its address; the Illinois list covers it. Illinois's other cities with a page of their own: Chicago, Rockford, Naperville and Springfield.
Against Illinois and its other counties
Shares of tests people chose to run and report, by county (2017); the state's is its counties' counts added up, calculated by Radon411. Only a test measures a home.
The counties around St. Charles
By distance from the middle of St. Charles; counties with 30 or more tests.
The median reported pre-mitigation result for 2017 was 2.8 pCi/L in Kane County and 2.7 pCi/L in DuPage County.
Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2017.
St. Charles, Geology
The ground under St. Charles
PredictedUSGS's geologic map puts all of St. Charles' mapped land in one class: high radon potential. All of it lies in the area the map calls Bloomington Ridged Plain, to which USGS gives 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 |
|---|---|---|---|---|
| Bloomington Ridged Plain | Wisconsinan glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
St. Charles beside its counties and Illinois
All of St. Charles, like all of Kane County, is rated high. St. Charles has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%.
The map rates the ground, not the air in any home.
St. Charles, Homes
Homes in St. Charles
Of St. Charles' 13,780 homes, 61% are detached houses, against 69% across Kane County; 18% are in buildings of five or more homes. Half of its homes were built before 1985, close to Kane County's 1984: 17% date from before 1960 and 25% from 2000 or later. 70% of occupied homes are lived in by their owner (Kane County: 76%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | St. Charles | Kane County | Illinois |
|---|---|---|---|
| Housing units | 13,780 | 189,918 | 5,443,501 |
| Detached houses | 61% | 69% | 58% |
| In buildings of 5 or more | 18% | 12% | 22% |
| Mobile homes | 0% | 1% | 2% |
| Built before 1960 | 17% | 25% | 38% |
| Built since 2000 | 25% | 28% | 16% |
| Middle year built | 1985 | 1984 | 1970 |
| Owner-occupied | 70% | 76% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.
Local help
St. Charles, Local resources
Local resources for St. Charles
Who to ask in Illinois: its radon program, test kits and professionals.
- IEMA-OHS Radon ProgramRun by Illinois Emergency Management Agency and Office of Homeland Security, phone (800) 325-1245.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 IllinoisRadon testers and mitigators in Illinois, each with how its listing was checked.
The program's own words on licensing and disclosure are on the Illinois page.
What it means
St. Charles, Questions
Questions about radon in St. Charles
What radon zone is St. Charles in?
A zone line runs through St. Charles: Kane County in Zone 1 and DuPage County in Zone 2. 97.2% of the city's land is in Kane County, so Zone 1 covers most addresses. Which zone applies depends on the county an address is in.
What are radon levels in St. Charles?
Around St. Charles, 36.6% of 8,682 tests reported from Kane County for 2017 reached 4 pCi/L or more, so a high result is no surprise here. The median reported result was 2.8 pCi/L. DuPage County reported 33.7% of 19,401 tests; the counties are kept apart.
Should I test my home in St. Charles?
Yes. Kane County reported about 3,178 of its 8,682 tests at or above 4 pCi/L. That is above Illinois' pooled 33.7%, and ranks Kane County 47th of the 70 Illinois counties with 30 or more tests. Which homes they were, no map can say. How to test a home.
What ground is St. Charles built on, as far as radon goes?
USGS's geologic map puts all of St. Charles on one named area, "Bloomington Ridged Plain", rated high for radon potential, radon index 13.
Is radon higher in the counties around St. Charles?
It depends which way you go. 3 of the 8 nearest counties with a figure report a larger share than Kane County's 36.6% and 5 a smaller one: from Cook County (19.4%, 26 miles off) to Boone County (46.9%, 38 miles off).
The answers use the published figures of Kane County and DuPage County, the counties St. Charles lies in.
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