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 Winnebago County, Wisconsin
EPA puts Winnebago County in Zone 2, its middle radon zone, and high results are common there: 42.4% of the 512 radon tests reported to CDC (2023) 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
42.4%
6.7 pts above WI
- Winnebago
- 42.4%
- Wisconsin
- 35.7%
512 tests, 2023
Median result
3.1pCi/L
Below action level
- Winnebago
- 3.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
512
7th of 69 by tests
- Winnebago
- 512
- Dane
- 2,887
Reported to CDC before any fix, 2023
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 Wisconsin
25 of 69
Middle half
- Winnebago
- 42.4%
- Langlade
- 65.8%
By share, of 69 with 30+ tests
Read a result for Winnebago County
Starts at Winnebago County's median, 3.1 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.1 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. Winnebago County's median reported result, 2023.
The data
Winnebago County, At a glance
Winnebago County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Winnebago County is a
USGS geologic potential: Moderate across 82% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Winnebago County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 43.7% |
| 2015 | 51.0% |
| 2016 | 48.9% |
| 2017 | 43.2% |
| 2019 | 43.3% |
| 2020 | 49.4% |
| 2021 | 48.8% |
| 2022 | 54.9% |
| 2023 | 42.4% |
2023: 42.4%. Across these years the share ran from 42.4% to 54.9%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 512 tests reported to CDC for Winnebago County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Winnebago County, Compared
Winnebago County radon figures, compared
Calculated by Radon411In Winnebago County, about 4 in 10 reported tests in 2023 (217 of 512) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 9.0 points higher. Across 72 Wisconsin counties pooled together, 35.7% of tests reached that level, so Winnebago County runs 6.7 points above its state.
Of 6 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 4 a smaller one; the spread is 19.6% (Fond du Lac County) to 52.8% (Waupaca County). By share, Winnebago County is 25th of 69 Wisconsin counties with 30 or more tests for the same period.
Year by year, 2014 opened at 43.7% and 2023 closed at 42.4% (about level), with 2022 the high at 54.9%. Half the tests came in under 3.1 pCi/L and half over it; the single highest reached 67.1 pCi/L. Below the action level, 175 tests (34.2%) came in under 2 pCi/L, against 41.4% statewide, and 120 tests (23.4%) fell between 2 and 4, against 23.0% statewide.
Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 42.4% share point the same way here. USGS geology rates 82% of the county's land moderate radon potential. CDC also counts 28 tests taken after mitigation in Winnebago County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2023, with 512 tests reported; the quietest, 2017, had 243.
Winnebago CountyWisconsin, pooled
| Year | Tests | Winnebago County, at or above 4 pCi/L | Wisconsin, pooled |
|---|---|---|---|
| 2014 | 309 | 43.7% | 51.1% |
| 2015 | 310 | 51.0% | 51.6% |
| 2016 | 370 | 48.9% | 45.2% |
| 2017 | 243 | 43.2% | 44.8% |
| 2019 | 351 | 43.3% | 42.9% |
| 2020 | 314 | 49.4% | 27.0% |
| 2021 | 258 | 48.8% | 39.9% |
| 2022 | 510 | 54.9% | 42.9% |
| 2023 | 512 | 42.4% | 35.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Winnebago County, Geology
The ground under Winnebago County
PredictedMost of the ground under Winnebago County is one class on USGS's geologic map: 81.5% of its land is moderate radon potential, with 18.5% high. The map puts 81.5% of Winnebago County in the area it calls Green Bay Lobe and 18.5% in Eastern Ridges and Lowlands. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 12, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Green Bay Lobe | Glacial deposits derived from carbonate and igneous rocks. | Moderate | 10 | 81.5% |
| Eastern Ridges and Lowlands | Glacial deposits derived from Ordovician carbonate rocks. | High | 12 | 18.5% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Winnebago County beside the ground around it
Wisconsin as a whole has more high-potential ground than Winnebago County: 34.8% of its land, against 18.5% here. Of the 6 counties that border it, 4 have more high-potential ground, Fond du Lac County the most at 89.4%.
The map rates the ground, not the air in any home.
Local help
Winnebago County, Local resources
Radon testing and mitigation in Winnebago County
- Wisconsin's radon programWisconsin Department of Health ServicesWisconsin's radon program does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Wisconsin.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
We recommend starting with your regional Radon Information Center since many centers provide test kits for free or reduced cost, and often with laboratory fees covered.
- Compare kits
- Professionals in Wisconsin19 professionals are listed in Wisconsin.
What Wisconsin's program says
- Phone
- 1-888-569-7236
- DHSRadon@dhs.wisconsin.gov
- Licensing of radon professionals
The State of Wisconsin does not require contractors performing radon measurement or mitigation work to be state licensed or nationally certified.
What it means
Winnebago County, Questions
Questions about radon in Winnebago County
Are radon levels high in Winnebago County?
In 2023, 42.4% of the radon tests reported to CDC for Winnebago County, Wisconsin were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.1 pCi/L. Of 69 Wisconsin counties with 30 or more tests for the same period, 24 reported a higher share; pooled, the state comes to 35.7%.
Which counties border Winnebago County?
Winnebago County borders 6 counties: Calumet County, Outagamie County, Fond du Lac County, Waupaca County, Green Lake County and Waushara County.
Products
Winnebago County, Products
Testing a home in Winnebago County
In Winnebago County, 42.4% of 512 tests reported to CDC in 2023 reached 4 pCi/L, against 35.7% pooled across Wisconsin. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Winnebago 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
MonitorAEGTEST
HOUND-3786 rechargeable radon monitor with a 3.5-inch color screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Winnebago County, Bordering counties
Counties bordering Winnebago County
Calculated by Radon411- Radon levels in Waupaca CountyEPA zone 1
52.8%at or above 4 pCi/L
Median 4.3 pCi/L · 127 tests · 10.4 points above Winnebago County
- Radon levels in Calumet CountyEPA zone 2
51.6%at or above 4 pCi/L
Median 4.4 pCi/L · 122 tests · 9.2 points above Winnebago County
- Radon levels in Outagamie CountyEPA zone 2
40.7%at or above 4 pCi/L
Median 3.1 pCi/L · 337 tests · 1.7 points below Winnebago County
- Radon levels in Green Lake CountyEPA zone 1
40.5%at or above 4 pCi/L
Median 3.4 pCi/L · 79 tests · 1.9 points below Winnebago County
- Radon levels in Waushara CountyEPA zone 2
25.4%at or above 4 pCi/L
Median 1.9 pCi/L · 71 tests · 17.0 points below Winnebago County
- Radon levels in Fond du Lac CountyEPA zone 1
19.6%at or above 4 pCi/L
Median 1.4 pCi/L · 984 tests · 22.8 points below Winnebago County
Winnebago County, Cities and towns
Cities and towns in Winnebago County
The Census Bureau estimates 174,218 residents in Winnebago County for July 1, 2025, 2,385 more than in 2020 (+1.4%). That works out to 401 people per square mile of land. Appleton, the largest place on its list (75,452 residents in all), extends beyond Winnebago County, so no share of the total is worked out for it. CDC's 512 reported tests for 2023 work out to 2.9 per 1,000 residents (2025 estimate), close to Wisconsin's 3.5.
From Appleton to Winneconne, CDC publishes no figure by town: each reads Winnebago County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Appletonextends beyond Winnebago County | 75,452 | −0.2% | Counted whole |
| Oshkosh | 67,460 | +0.8% | 38.7% |
| Neenah | 27,638 | +0.9% | 15.9% |
| Fox Crossing | 19,320 | +1.8% | 11.1% |
| Menashaextends beyond Winnebago County | 18,385 | +0.6% | Counted whole |
| Omro | 3,639 | −0.7% | 2.1% |
| Winneconne | 2,498 | −1.3% | 1.4% |
Places in Winnebago County with a city page: 1 of 2
7 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 Winnebago County is counted whole, so it has no share.
Winnebago County, Homes
Homes in Winnebago County
Of Winnebago County's 76,770 homes, 66% are detached houses, against 66% across Wisconsin; 19% are in buildings of five or more homes. Half of its homes were built before 1975, close to Wisconsin's 1975: 34% date from before 1960 and 18% from 2000 or later. 66% of occupied homes are lived in by their owner (Wisconsin: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Winnebago County | Wisconsin |
|---|---|---|
| Housing units | 76,770 | 2,750,750 |
| Detached houses | 66% | 66% |
| In buildings of 5 or more | 19% | 17% |
| Mobile homes | 2% | 3% |
| Built before 1960 | 34% | 34% |
| Built since 2000 | 18% | 20% |
| Middle year built | 1975 | 1975 |
| Owner-occupied | 66% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.