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Radon Levels in Will County, Illinois

EPA puts Will County in Zone 2, its middle radon zone, and high results are common there: 40.0% of the 10,776 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

    40.0%

    6.3 pts above IL

    Will
    40.0%
    Illinois
    33.7%

    10,776 tests, 2017

  • Median result

    3.1pCi/L

    Below action level

    Will
    3.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    10,776

    4th of 70 by tests

    Will
    10,776
    Cook
    26,937

    Reported to CDC before any fix, 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Illinois

    42 of 70

    Middle half

    Will
    40.0%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Will County

Starts at Will County's median, 3.1 pCi/L

3.1pCi/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

  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. Will County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Will County, At a glance

Will County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Will County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: High across 60% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Will County, 2017

Share of reported tests at or above 4 pCi/L, by year, Will County
Share of reported tests at or above 4 pCi/L, by year, Will County
YearShare of reported tests at or above 4 pCi/L
201442.0%
201542.3%
201618.6%
201740.0%

2017: 40.0%. Across these years the share ran from 18.6% to 42.3%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 10,776 tests reported to CDC for Will 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

Will County, Compared

Will County radon figures, compared

Calculated by Radon411

In Will County, about 4 in 10 reported tests in 2017 (4,314 of 10,776) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 8.3 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Will County runs 6.3 points above its state.

Of 6 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 19.4% (Cook County) to 36.6% (Kane County). By share, Will County is 42nd of 70 Illinois counties with 30 or more tests for the same period.

Year by year, 2014 opened at 42.0% and 2017 closed at 40.0% (down 2.0 points), with 2015 the high at 42.3%. Half the tests came in under 3.1 pCi/L and half over it; the single highest reached 203.5 pCi/L. Below the action level, 3,495 tests (32.4%) came in under 2 pCi/L, against 37.7% statewide, and 2,967 tests (27.5%) fell between 2 and 4, against 28.6% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 40.0% share point the same way here. USGS geology rates 60% of the county's land high radon potential.

The busiest year on file was 2014, with 13,263 tests reported; the quietest, 2016, had 306.

Share of reported tests at or above 4 pCi/L by year, Will County against Illinois2014 to 2017, years with 30 or more tests: Will County 42.0% to 40.0%, the state's pooled share 33.7% in 2017.
Will CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Will County against Illinois: data table
YearTestsWill County, at or above 4 pCi/LIllinois, pooled
201413,26342.0%37.8%
20157,91742.3%36.6%
201630618.6%17.4%
201710,77640.0%33.7%
Will County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Will County
Will County10,77640.0%3.1 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−6.3 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−8.3 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+29.2 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−31.6 points
Kane County, ILborders it8,68236.6%2.8 pCi/L−3.4 points
Kendall County, ILborders it3,04535.0%2.8 pCi/L−5.0 points
DuPage County, ILborders it19,40133.7%2.7 pCi/L−6.3 points
Grundy County, ILborders it39032.3%2.4 pCi/L−7.7 points
Kankakee County, ILborders it52231.6%2.7 pCi/L−8.4 points
Cook County, ILborders it26,93719.4%1.9 pCi/L−20.6 points
Where Will County's reported results fell, 2017, beside Illinois and the United States
ResultWill County testsWill County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L3,49532.4%37.7%43.5%−5.3 points
2 to 4 pCi/L2,96727.5%28.6%24.8%−1.1 points
4 pCi/L and above4,31440.0%33.7%31.7%+6.3 points
Will 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
Whiteside County37 of 7069643.1%3.3 pCi/L
McLean County38 of 704,54842.5%3.3 pCi/L
Christian County39 of 7021342.3%3.5 pCi/L
DeKalb County40 of 701,70741.1%3.3 pCi/L
Peoria County41 of 703,81640.2%3.1 pCi/L
Will County42 of 7010,77640.0%3.1 pCi/L
Monroe County43 of 7071439.9%3.0 pCi/L
Macon County44 of 701,25138.8%3.1 pCi/L
Effingham County45 of 7014138.3%2.7 pCi/L
Clinton County46 of 7058237.6%3.0 pCi/L
Kane County47 of 708,68236.6%2.8 pCi/L
Will County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
201710,77640.0%3.1 pCi/L203.5 pCi/L33.7%+21.4 points
201630618.6%1.2 pCi/L20.2 pCi/L17.4%−23.7 points
20157,91742.3%3.2 pCi/L115.5 pCi/L36.6%+0.3 points
201413,26342.0%3.2 pCi/L165.8 pCi/L37.8%First on file

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

Will County, Geology

The ground under Will County

Predicted

USGS's geologic map splits Will County: 59.8% of its land is high radon potential and 40.2% moderate. The map puts 59.8% of Will County in the area it calls Bloomington Ridged Plain and 40.2% in Wheaton Morainal Country. USGS gives the first a radon index of 13, in the high band (12 to 17), and the second 11, in the moderate band (9 to 11).

USGS's geologic areas under Will County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Bloomington Ridged PlainWisconsinan glacial deposits and loess over Paleozoic sedimentary rocks.High1359.8%
Wheaton Morainal CountryGlacial lake deposits and clay-rich glacial till.Moderate1140.2%

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

Will County beside the ground around it

On high-potential ground Will County is close to Illinois as a whole: 59.8% of its land against 64.5%. Of the 7 counties that border it, 4 have more high-potential ground, Grundy County the most at 100%.

Share of land by USGS radon potential: Will County, the 7 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Will CountyZone 2None40.2%59.8%
Kankakee CountyZone 2None37.1%62.9%
Cook CountyZone 2None96.8%3.2%
DuPage CountyZone 2None80.1%19.9%
Lake County, INZone 2None99.3%None
Kendall CountyZone 1NoneNone100%
Grundy CountyZone 1NoneNone100%
Kane 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

Will County, Local resources

Radon testing and mitigation in Will County

Listed radon businesses with an address in Will County:

Listed radon professionals by town: Aurora, Naperville, Joliet, Bolingbrook, Orland Park, Tinley Park, Plainfield, Oswego, Woodridge, New Lenox, Lockport, Homer Glen, Crest Hill, Mokena, Shorewood, Lemont, Manhattan, Monee, Peotone

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

Will County, Questions

Questions about radon in Will County

Are radon levels high in Will County?

In 2017, 40.0% of the radon tests reported to CDC for Will County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.1 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 41 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Will County?

Will County borders 7 counties: Kankakee County, IL, Cook County, IL, DuPage County, IL, Lake County, IN, Kendall County, IL, Grundy County, IL and Kane County, IL.

Products

Will County, Products

Testing a home in Will County

In Will County, 40.0% of 10,776 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Will County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Will County homes, compared

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Will County, Bordering counties

Counties bordering Will County

Calculated by Radon411

Will County, Cities and towns

Cities and towns in Will County

The Census Bureau estimates 712,253 residents in Will County for July 1, 2025, 15,352 more than in 2020 (+2.2%). That works out to 852 people per square mile of land. Aurora, the largest place on its list (181,505 residents in all), extends beyond Will County, so no share of the total is worked out for it. CDC's 10,776 reported tests for 2017 work out to 15.1 per 1,000 residents (2025 estimate), close to Illinois' 10.9.

From Aurora to Symerton, CDC publishes no figure by town: each reads Will County's.

The 12 largest cities and towns in Will County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Auroraextends beyond Will County181,505+0.7%Counted whole
Napervilleextends beyond Will County153,114+2.5%Counted whole
Jolietextends beyond Will County152,241+1.2%Counted whole
Bolingbrookextends beyond Will County74,803+1.3%Counted whole
Orland Parkextends beyond Will County57,954−1.0%Counted whole
Tinley Parkextends beyond Will County55,140−1.2%Counted whole
Plainfieldextends beyond Will County50,043+11.3%Counted whole
Romeoville41,281+1.2%5.8%
Oswegoextends beyond Will County39,948+15.0%Counted whole
Woodridgeextends beyond Will County34,028−0.2%Counted whole
New Lenox28,893+6.0%4.1%
Lockport27,822+6.4%3.9%
  • Homer Glen (part)
  • Frankfort (part)
  • Park Forest (part)
  • Crest Hill
  • Mokena
  • Shorewood
  • Lemont (part)
  • Channahon (part)
  • Minooka (part)
  • Manhattan
  • Steger (part)
  • Crete (part)
  • University Park (part)
  • Braidwood (part)
  • Coal City (part)
  • Wilmington
  • Monee
  • Beecher
  • Peotone
  • Diamond (part)
  • Elwood
  • Rockdale
  • Braceville (part)
  • Godley (part)
The other 1 place in Will County
  • Symerton

37 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 Will County is counted whole, so it has no share.

Will County, Homes

Homes in Will County

Of Will County's 252,684 homes, 75% are detached houses, against 58% across Illinois; 8% are in buildings of five or more homes. Much of Will County is recent building: 32% of its homes have gone up since 2000 and the middle year built is 1992, against 1970 for Illinois. Owners live in 83% of the occupied homes (Illinois: 67%), so for most households a test and a fix are their own to order.

Homes in Will County, Illinois, 2019 to 2023
HomesWill CountyIllinois
Housing units252,6845,443,501
Detached houses75%58%
In buildings of 5 or more8%22%
Mobile homes1%2%
Built before 196016%38%
Built since 200032%16%
Middle year built19921970
Owner-occupied83%67%

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