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Illinois Radon Map and Levels by County

Illinois's counties span all three EPA radon zones. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    37.8%

    2.8 pts above U.S.

    Illinois
    37.8%
    U.S.
    34.9%

    187,881 tests across 98 counties, 2014

  • Rank among states

    7 of 19

    Ten highest states

    Illinois
    37.8%
    Connecticut
    53.1%

    By share, every state pooled the same way, 2014

  • Counties in EPA Zone 1

    56 of 102

    Most at highest potential

    Zone 1
    56
    Zone 2
    43

    Most counties sit in Zone 1; Zone 1 is the highest potential

  • Highest county

    100.0%

    Putnam County

    Putnam
    100.0%
    Fayette
    12.5%

    Counties with 30+ tests, 2014

Read a result for Illinois

Starts at EPA's action level

4.0pCi/L

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

EPA’s reading of 4.0 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. 37.8% of Illinois's reported tests reached 4 pCi/L, 2014.

Interpret this readingWhat a fix costs

The data

Illinois, At a glance

Illinois at a glance

Predicted: EPA radon zone

102 of 102 counties classified

EPA classifies counties, not states. Of the 102 counties in Illinois with a zone, 56 are in Zone 1, 43 in Zone 2 and 3 in Zone 3.

  • Zone 1: Highest predicted potentialgreater than 4 pCi/L56 of 102 counties · 54.9%
  • Zone 2: Moderate predicted potential2 to 4 pCi/L43 of 102 counties · 42.2%
  • Zone 3: Lower predicted potentialless than 2 pCi/L3 of 102 counties · 2.9%

An EPA radon zone predicts a whole county. It is not intended to determine whether any individual home should be tested: homes with elevated levels occur in all three zones, and EPA recommends testing every home regardless of zone.

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

CDC test figures, county by county

CDC publishes Illinois's radon test figures by county: 102 of its 102 counties have one. Each one's share is in the county list.

How to read these figures

Illinois, Compared

Illinois radon figures, compared

Calculated by Radon411
Illinois, 2014
37.8%
of 187,881 tests at or above 4 pCi/L, pooled
Against the U.S.
+2.8points
34.9% pooled
Rank among the states
7 of 19
1 is the highest share
Counties with 30 or more tests
74
Highest
100.0%
Putnam County
Lowest
12.5%
Fayette County

Illinois pools to 37.8%: that share of 187,881 reported tests from 98 counties in 2014 reached EPA's action level. Nationally the pooled share is 34.9%: 2.8 points lower than here.

Among 19 states pooled the same way it ranks 7th, with Minnesota (42.9%) above it and Pennsylvania (36.1%) below. Putnam County reports the highest share (100.0% of 54 tests) and Fayette County the lowest (12.5%); the most tests came from Cook County, 36,777 of them at 20.5%.

Year by year (4 years pooled), the share went from 37.8% (2014) to 33.7% (2017), down 4.0 points, with 2014 the highest at 37.8%. By band, 33 counties at 50% or more, 28 counties at 30% to 50%, 12 counties at 15% to 30%, 1 county at 5% to 15%.

EPA's 1993 map puts 56 of its 102 classified counties in Zone 1; the tests reported since bear that out at 37.8%.

Illinois ranked among 19 states by pooled share of tests at or above 4 pCi/L, 2014
StateRankCountiesTestsAt or above 4 pCi/L
Wisconsin2 of 197216,18551.1%
Nebraska3 of 198556,51750.5%
Colorado4 of 19588,11346.5%
Utah5 of 19263,40943.4%
Minnesota6 of 198739,97442.9%
Illinois7 of 1998187,88137.8%
Pennsylvania8 of 196778,92236.1%
Missouri9 of 19983,05034.4%
Alaska10 of 1996428.1%
Florida11 of 194310,82825.7%
Oregon12 of 19325,71025.1%
Illinois' highest and lowest counties with 30 or more tests, by share at or above 4 pCi/L, 2014
CountyRankTestsAt or above 4 pCi/L
Putnam County1 of 7454100.0%
Stark County2 of 743080.0%
Marshall County3 of 747876.9%
Warren County4 of 747275.0%
Carroll County5 of 7431873.6%
De Witt County6 of 749073.3%
Stephenson County7 of 7438467.2%
Bureau County8 of 7442067.1%
Knox County9 of 7439665.2%
Henry County10 of 7478664.1%
Fayette County74 of 744812.5%
Jersey County73 of 7412918.6%
Randolph County72 of 746020.0%
Cook County71 of 7436,77720.5%
Clinton County70 of 7431822.6%
Illinois' counties with 30 or more tests, by their own share at or above 4 pCi/L, 2014
ShareCountiesTheir testsFor example
50% or more3324,495Putnam County, Stark County, Marshall County
30% to 50%28124,545Sangamon County, Coles County, McLean County
15% to 30%1238,463Livingston County, Montgomery County, Pike County
5% to 15%148Fayette County
Under 5%00None
Illinois pooled by year, against the United States
YearCountiesTestsAt or above 4 pCi/LUnited StatesChange from the row before
201793138,00633.7%31.7%+16.3 points
2016335,64917.4%31.2%−19.2 points
20159299,26436.6%35.5%−1.2 points
201498187,88137.8%34.9%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period. CDC publishes no state or national figure.

Illinois, Counties

Illinois counties by EPA zone

Predicted

The map of Illinois, then its 102 counties zone by zone, each with its reported share at or above 4 pCi/L and a report of its own.

Illinois radon map by county: EPA radon zones. Map of Illinois's 102 counties shaded by EPA radon zone: Zone 1 in red-orange, Zone 2 in amber, Zone 3 in pale sand. 56 in Zone 1, 43 in Zone 2, 3 in Zone 3.
Illinois radon map by countyEPA radon zones for Illinois's counties: 56 counties in Zone 1, 43 counties in Zone 2, 3 counties in Zone 3.A prediction for each county, not a reading of any home; elevated homes occur in all three zones.

The 12 highest in Illinois, 2014

Zone 1: highest predicted potential56

Local help

Illinois, Local resources

Local resources in Illinois

Who to ask in Illinois: its radon program, test kits and professionals.

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

Illinois, Questions

Questions about radon in Illinois

Is radon a problem in Illinois?

Illinois has 102 counties on EPA's Map of Radon Zones: Zone 1, the highest predicted potential, for 56; Zone 2 for 43; Zone 3 for 3. Pooled from 98 counties, 37.8% of the 187,881 radon tests reported to CDC in 2014 were at or above 4 pCi/L, 7th of 19 states.

Who does radon mitigation in Illinois?

Radon411's Illinois directory lists 339 radon businesses for testing, mitigation or both, each with the licensing list it was read from.

Which Illinois counties are in EPA radon Zone 1?

56 counties are in Zone 1: Adams County, Boone County, Brown County, Bureau County, Calhoun County, Carroll County, Cass County, Champaign County, and 48 more in the county table on this page.

Which Illinois counties have the highest radon?

By the share of reported tests at or above 4 pCi/L, 2014: Putnam County 100.0% (54 tests), Stark County 80.0% (30 tests), Marshall County 76.9% (78 tests), Warren County 75.0% (72 tests), Carroll County 73.6% (318 tests).

Which EPA region is Illinois in?

Illinois is in EPA Region 5: Great Lakes.

Products

Illinois, Products

Testing a home in Illinois

37.8% of the 187,881 tests reported to CDC for Illinois in 2014 reached 4 pCi/L: a short-term kit (2 to 90 days) gives a first answer in days, a long-term test the year-round average. A short-term kit (2 to 90 days) is the quick first check for a home in Illinois; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Illinois homes, compared

Explore

Cities in Illinois with their own page

Radon data is published by county, not by city. Each city page sets the figures of the counties the city lies in side by side.