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Radon Levels in Ogle County, Illinois

EPA puts Ogle County in Zone 1, its highest radon zone, and high results are common there: 52.4% of the 636 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    52.4%

    18.7 pts above IL

    Ogle
    52.4%
    Illinois
    33.7%

    636 tests, 2017

  • Median result

    4.1pCi/L

    Action level reached

    Ogle
    4.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    636

    24th of 70 by tests

    Ogle
    636
    Cook
    26,937

    Reported to CDC before any fix, 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Illinois

    18 of 70

    Top quarter

    Ogle
    52.4%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Ogle County

Starts at Ogle County's median, 4.1 pCi/L

4.1pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 4.1 pCi/L

At or above 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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. Ogle County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Ogle County, At a glance

Ogle County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Ogle County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

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 Ogle County, 2017

Share of reported tests at or above 4 pCi/L, by year, Ogle County
Share of reported tests at or above 4 pCi/L, by year, Ogle County
YearShare of reported tests at or above 4 pCi/L
201461.9%
201545.8%
2016100.0%
201752.4%

2017: 52.4%. Across these years the share ran from 45.8% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 636 tests reported to CDC for Ogle 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).

How to read these figures

Ogle County, Compared

Ogle County radon figures, compared

Calculated by Radon411

More than half: 52.4% of the 636 radon tests reported to CDC for Ogle County in 2017 read at least 4 pCi/L. That places it 18th of 70 Illinois counties with 30 or more tests for the same period. That is 18.7 points above the 33.7% pooled from 93 Illinois counties.

The median result, 4.1 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 51.5 pCi/L. The rest split 19.3% under 2 pCi/L and 28.3% from 2 to 4 (Illinois: 37.7% and 28.6%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 52.4% share point the same way here.

2 of its 7 bordering counties with figures ran higher, led by Carroll County at 62.9%; Winnebago County reported 34.9%. Statewide for the same period, Stark County reported the highest share (69.2%) and Williamson County the lowest (8.4%).

The busiest year on file was 2014, with 678 tests reported; the quietest, 2016, had 3.

Over 3 years of annual figures the share fell 9.5 points, from 61.9% in 2014 to 52.4% in 2017; its peak was 61.9% in 2014. Nationally, every county with a figure for the same period pools to 31.7%; Ogle County sits 20.7 points above it.

Share of reported tests at or above 4 pCi/L by year, Ogle County against Illinois2014 to 2017, years with 30 or more tests: Ogle County 61.9% to 52.4%, the state's pooled share 33.7% in 2017.
Ogle CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Ogle County against Illinois: data table
YearTestsOgle County, at or above 4 pCi/LIllinois, pooled
201467861.9%37.8%
201517745.8%36.6%
201763652.4%33.7%
Ogle County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Ogle County
Ogle County63652.4%4.1 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−18.7 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−20.7 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+16.8 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−44.0 points
Carroll County, ILborders it21062.9%5.5 pCi/L+10.5 points
Stephenson County, ILborders it51957.2%4.8 pCi/L+4.8 points
Boone County, ILborders it52546.9%3.4 pCi/L−5.5 points
Lee County, ILborders it21943.8%3.3 pCi/L−8.6 points
Whiteside County, ILborders it69643.1%3.3 pCi/L−9.3 points
DeKalb County, ILborders it1,70741.1%3.3 pCi/L−11.3 points
Winnebago County, ILborders it2,70334.9%2.9 pCi/L−17.5 points
Where Ogle County's reported results fell, 2017, beside Illinois and the United States
ResultOgle County testsOgle County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L12319.3%37.7%43.5%−18.4 points
2 to 4 pCi/L18028.3%28.6%24.8%−0.3 points
4 pCi/L and above33352.4%33.7%31.7%+18.7 points
Ogle County ranked among the 70 Illinois counties with 30 or more tests, by share at or above 4 pCi/L, 2017
CountyRankTestsAt or above 4 pCi/LMedian
McDonough County12 of 7021055.7%4.3 pCi/L
Piatt County14 of 7027954.8%4.3 pCi/L
Vermilion County15 of 703953.8%4.7 pCi/L
Putnam County16 of 704553.3%4.5 pCi/L
Woodford County17 of 7076552.9%4.2 pCi/L
Ogle County18 of 7063652.4%4.1 pCi/L
Menard County19 of 7016851.8%4.3 pCi/L
Coles County20 of 7019851.5%4.2 pCi/L
Douglas County21 of 708450.0%3.8 pCi/L
Warren County21 of 704250.0%3.6 pCi/L
Marshall County23 of 708148.1%3.8 pCi/L
Ogle County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
201763652.4%4.1 pCi/L51.5 pCi/L33.7%−47.6 points
20163100.0%6.3 pCi/L6.3 pCi/L17.4%+54.2 points
201517745.8%3.7 pCi/L24.8 pCi/L36.6%−16.1 points
201467861.9%5.3 pCi/L37.5 pCi/L37.8%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Ogle County, Geology

The ground under Ogle County

Predicted

USGS's geologic map puts all of Ogle County's mapped land in one class: high radon potential. 96.9% of it lies in the area the map calls Galesburg Plain, to which USGS gives a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Ogle County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Galesburg PlainIllinoian glacial deposits and loess over Paleozoic sedimentary rocks.High1396.9%
Bloomington Ridged PlainWisconsinan glacial deposits and loess over Paleozoic sedimentary rocks.High133.1%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Ogle County beside the ground around it

Ogle County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 7 counties that border it, none has as large a share of high-potential ground; Boone County comes nearest at 100%.

Share of land by USGS radon potential: Ogle County, the 7 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Ogle CountyZone 1NoneNone100%
Lee CountyZone 1NoneNone100%
Winnebago CountyZone 1NoneNone100%
Stephenson CountyZone 1NoneNone100%
DeKalb CountyZone 1NoneNone100%
Carroll CountyZone 1NoneNone100%
Boone CountyZone 1NoneNone100%
Whiteside CountyZone 1NoneNone100%
Illinois102 counties, pooled by land areaVaries0.9%34.5%64.5%

The map rates the ground, not the air in any home.

Local help

Ogle County, Local resources

Radon testing and mitigation in Ogle County

Listed radon businesses with an address in Ogle County:

Listed radon professionals by town: Rockford, Oregon

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

Ogle County, Questions

Questions about radon in Ogle County

Are radon levels high in Ogle County?

In 2017, 52.4% of the radon tests reported to CDC for Ogle County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.1 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 17 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Ogle County?

Ogle County borders 7 counties: Lee County, Winnebago County, Stephenson County, DeKalb County, Carroll County, Boone County and Whiteside County.

Products

Ogle County, Products

Testing a home in Ogle County

In Ogle County, 52.4% of 636 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Ogle 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

Ogle County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Ogle County

Explore

Ogle County, Bordering counties

Counties bordering Ogle County

Calculated by Radon411

Ogle County, Cities and towns

Cities and towns in Ogle County

About 51,399 people live in Ogle County by the Census Bureau's estimate for July 1, 2025, 366 fewer than in 2020 (−0.7%). That works out to 68 people per square mile of land. Rockford, the largest place on its list (147,384 residents in all), extends beyond Ogle County, so no share of the total is worked out for it. CDC's 636 reported tests for 2017 work out to 12.4 per 1,000 residents (2025 estimate), close to Illinois' 10.9.

From Rockford to Adeline, CDC publishes no figure by town: each reads Ogle County's.

The 12 largest cities and towns in Ogle County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Rockfordextends beyond Ogle County147,384−0.9%Counted whole
Rochelleextends beyond Ogle County9,498+0.3%Counted whole
Byron3,777−0.2%7.3%
Oregon3,573−1.6%7.0%
Mount Morris2,787−2.1%5.4%
Davis Junction2,566+2.2%5.0%
Polo2,235−2.1%4.3%
Forreston1,402−2.2%2.7%
Hillcrest1,210−1.4%2.4%
Stillman Valley1,058−1.4%2.1%
Creston637+1.3%1.2%
Leaf River417−2.3%0.8%
  • Monroe Center
  • Adeline

14 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Ogle County is counted whole, so it has no share.

Ogle County, Homes

Homes in Ogle County

Ogle County is a place of houses on their own lots: 83% of its 22,625 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1972, close to Illinois' 1970: 35% date from before 1960 and 15% from 2000 or later. 75% of occupied homes are lived in by their owner (Illinois: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Ogle County, Illinois, 2019 to 2023
HomesOgle CountyIllinois
Housing units22,6255,443,501
Detached houses83%58%
In buildings of 5 or more8%22%
Mobile homes3%2%
Built before 196035%38%
Built since 200015%16%
Middle year built19721970
Owner-occupied75%67%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.