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Radon Levels in Champaign County, Illinois

EPA puts Champaign County in Zone 1, its highest radon zone, and high results are common there: 44.7% of the 3,159 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

    44.7%

    11.0 pts above IL

    Champaign
    44.7%
    Illinois
    33.7%

    3,159 tests, 2017

  • Median result

    3.4pCi/L

    Below action level

    Champaign
    3.4 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    3,159

    12th of 70 by tests

    Champaign
    3,159
    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

    33 of 70

    Middle half

    Champaign
    44.7%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Champaign County

Starts at Champaign County's median, 3.4 pCi/L

3.4pCi/L

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

EPA’s reading of 3.4 pCi/L

Between 2 and 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Champaign County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Champaign County, At a glance

Champaign County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Champaign 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 Champaign County, 2017

Share of reported tests at or above 4 pCi/L, by year, Champaign County
Share of reported tests at or above 4 pCi/L, by year, Champaign County
YearShare of reported tests at or above 4 pCi/L
201452.4%
201551.2%
201650.0%
201744.7%

2017: 44.7%. Across these years the share ran from 44.7% to 52.4%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 3,159 tests reported to CDC for Champaign 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

Champaign County, Compared

Champaign County radon figures, compared

Calculated by Radon411

In Champaign County, about 4 in 10 reported tests in 2017 (1,413 of 3,159) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 13.0 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Champaign County runs 11.0 points above its state.

Of 5 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 42.5% (McLean County) to 57.1% (Ford County). By share, Champaign County is 33rd of 70 Illinois counties with 30 or more tests for the same period.

Year by year, 2014 opened at 52.4% and 2017 closed at 44.7% (down 7.7 points), with 2014 the high at 52.4%. Half the tests came in under 3.4 pCi/L and half over it; the single highest reached 47.2 pCi/L. Below the action level, 942 tests (29.8%) came in under 2 pCi/L, against 37.7% statewide, and 804 tests (25.5%) fell between 2 and 4, against 28.6% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 44.7% share point the same way here. USGS geology rates 100% of the county's land high radon potential.

The busiest year on file was 2014, with 4,500 tests reported; the quietest, 2016, had 6.

Share of reported tests at or above 4 pCi/L by year, Champaign County against Illinois2014 to 2017, years with 30 or more tests: Champaign County 52.4% to 44.7%, the state's pooled share 33.7% in 2017.
Champaign CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Champaign County against Illinois: data table
YearTestsChampaign County, at or above 4 pCi/LIllinois, pooled
20144,50052.4%37.8%
20151,92051.2%36.6%
20173,15944.7%33.7%
Champaign County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Champaign County
Champaign County3,15944.7%3.4 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−11.0 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−13.0 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+24.5 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−36.3 points
Ford County, ILborders it4257.1%4.0 pCi/L+12.4 points
Edgar County, ILborders it2157.1%4.5 pCi/L+12.4 points
Piatt County, ILborders it27954.8%4.3 pCi/L+10.1 points
Vermilion County, ILborders it3953.8%4.7 pCi/L+9.1 points
Douglas County, ILborders it8450.0%3.8 pCi/L+5.3 points
McLean County, ILborders it4,54842.5%3.3 pCi/L−2.2 points
Where Champaign County's reported results fell, 2017, beside Illinois and the United States
ResultChampaign County testsChampaign County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L94229.8%37.7%43.5%−7.9 points
2 to 4 pCi/L80425.5%28.6%24.8%−3.1 points
4 pCi/L and above1,41344.7%33.7%31.7%+11.0 points
Champaign 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
Tazewell County28 of 702,72446.4%3.6 pCi/L
Adams County29 of 7088546.1%3.6 pCi/L
Logan County30 of 707245.8%3.4 pCi/L
LaSalle County31 of 701,00245.8%3.6 pCi/L
Jo Daviess County32 of 7051345.0%3.5 pCi/L
Champaign County33 of 703,15944.7%3.4 pCi/L
Montgomery County34 of 7012343.9%3.3 pCi/L
Lee County35 of 7021943.8%3.3 pCi/L
Sangamon County36 of 703,37843.7%3.7 pCi/L
Whiteside County37 of 7069643.1%3.3 pCi/L
McLean County38 of 704,54842.5%3.3 pCi/L
Champaign County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
20173,15944.7%3.4 pCi/L47.2 pCi/L33.7%−5.3 points
2016650.0%5.1 pCi/L7.2 pCi/L17.4%−1.2 points
20151,92051.2%4.1 pCi/L50.8 pCi/L36.6%−1.2 points
20144,50052.4%4.2 pCi/L41.0 pCi/L37.8%First on file

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

Champaign County, Geology

The ground under Champaign County

Predicted

USGS's geologic map puts all of Champaign County's 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).

USGS's geologic areas under Champaign County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Bloomington Ridged PlainWisconsinan glacial deposits and loess over Paleozoic sedimentary rocks.High13100%

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

Champaign County beside the ground around it

Champaign County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 6 counties that border it, none has as large a share of high-potential ground; Douglas County comes nearest at 100%.

Share of land by USGS radon potential: Champaign County, the 6 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Champaign CountyZone 1NoneNone100%
Douglas CountyZone 1NoneNone100%
Piatt CountyZone 1NoneNone100%
Vermilion CountyZone 1NoneNone100%
Edgar CountyZone 1None5.1%94.9%
McLean CountyZone 1NoneNone100%
Ford CountyZone 1None0.8%99.2%
Illinois102 counties, pooled by land areaVaries0.9%34.5%64.5%

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

Local help

Champaign County, Local resources

Radon testing and mitigation in Champaign County

Listed radon businesses with an address in Champaign County:

Listed radon professionals by town: Champaign, Mahomet

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

Champaign County, Questions

Questions about radon in Champaign County

Are radon levels high in Champaign County?

In 2017, 44.7% of the radon tests reported to CDC for Champaign County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.4 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 32 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Champaign County?

Champaign County borders 6 counties: Douglas County, Piatt County, Vermilion County, Edgar County, McLean County and Ford County.

Products

Champaign County, Products

Testing a home in Champaign County

In Champaign County, 44.7% of 3,159 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Champaign 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

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

Explore

Champaign County, Bordering counties

Counties bordering Champaign County

Calculated by Radon411

Champaign County, Cities and towns

Cities and towns in Champaign County

The Census Bureau estimates 209,972 residents in Champaign County for July 1, 2025, 3,750 more than in 2020 (+1.8%). That works out to 211 people per square mile of land. Its largest town, Champaign, has 91,195 residents, 43.4% of the total. CDC's 3,159 reported tests for 2017 work out to 15.0 per 1,000 residents (2025 estimate), close to Illinois' 10.9.

From Champaign to Foosland, CDC publishes no figure by town: each reads Champaign County's.

The 12 largest cities and towns in Champaign County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Champaign91,195+3.2%43.4%
Urbana39,719+2.2%18.9%
Rantoul11,991−2.7%5.7%
Mahomet10,516+10.8%5.0%
Savoy9,113+2.8%4.3%
St. Joseph3,689−2.8%1.8%
Tolono3,499−2.3%1.7%
Fisher2,087+1.7%1.0%
Philo1,352−2.7%0.6%
Sidney1,167−2.9%0.6%
Homer1,050−2.2%0.5%
Thomasboro1,003−2.7%0.5%
  • Gifford
  • Ogden
  • Pesotum
  • Sadorus
  • Bondville
  • Broadlands
  • Ludlow
  • Royal
  • Ivesdale (part)
  • Allerton (part)
  • Longview
  • Foosland

24 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).

Champaign County, Homes

Homes in Champaign County

Champaign County has 94,351 homes, and many share a building: 33% are in buildings of five or more, 52% are detached houses, against 58% across Illinois. Much of Champaign County is recent building: 28% of its homes have gone up since 2000 and the middle year built is 1982, against 1970 for Illinois. 53% 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 Champaign County, Illinois, 2019 to 2023
HomesChampaign CountyIllinois
Housing units94,3515,443,501
Detached houses52%58%
In buildings of 5 or more33%22%
Mobile homes3%2%
Built before 196023%38%
Built since 200028%16%
Middle year built19821970
Owner-occupied53%67%

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