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Radon Levels in Logan County, Illinois

EPA puts Logan County in Zone 1, its highest radon zone, and high results are common there: 45.8% of the 72 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

    45.8%

    12.1 pts above IL

    Logan
    45.8%
    Illinois
    33.7%

    72 tests, 2017

  • Median result

    3.4pCi/L

    Below action level

    Logan
    3.4 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    72

    55th of 70 by tests

    Logan
    72
    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

    30 of 70

    Middle half

    Logan
    45.8%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Logan County

Starts at Logan 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. Logan County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Logan County, At a glance

Logan County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Logan 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 Logan County, 2017

Share of reported tests at or above 4 pCi/L, by year, Logan County
Share of reported tests at or above 4 pCi/L, by year, Logan County
YearShare of reported tests at or above 4 pCi/L
201456.5%
201554.3%
201745.8%

2017: 45.8%. Across these years the share ran from 45.8% to 56.5%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 72 tests reported to CDC for Logan 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

Logan County, Compared

Logan County radon figures, compared

Calculated by Radon411

In Logan County, about 5 in 10 reported tests in 2017 (33 of 72) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 14.1 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Logan County runs 12.1 points above its state.

Of 7 neighbours with a figure, 3 reported a larger share at or above 4 pCi/L and 4 a smaller one; the spread is 21.4% (Mason County) to 57.1% (De Witt County). By share, Logan County is 30th of 70 Illinois counties with 30 or more tests for the same period.

Year by year, 2014 opened at 56.5% and 2017 closed at 45.8% (down 10.7 points), with 2014 the high at 56.5%. Half the tests came in under 3.4 pCi/L and half over it; the single highest reached 18.2 pCi/L. Below the action level, 24 tests (33.3%) came in under 2 pCi/L, against 37.7% statewide, and 15 tests (20.8%) fell between 2 and 4, against 28.6% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 45.8% 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 138 tests reported; the quietest, 2017, had 72.

Share of reported tests at or above 4 pCi/L by year, Logan County against Illinois2014 to 2017, years with 30 or more tests: Logan County 56.5% to 45.8%, the state's pooled share 33.7% in 2017.
Logan CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Logan County against Illinois: data table
YearTestsLogan County, at or above 4 pCi/LIllinois, pooled
201413856.5%37.8%
201510554.3%36.6%
20177245.8%33.7%
Logan County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Logan County
Logan County7245.8%3.4 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−12.1 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−14.1 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+23.4 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−37.4 points
De Witt County, ILborders it12657.1%5.2 pCi/L+11.3 points
Menard County, ILborders it16851.8%4.3 pCi/L+6.0 points
Tazewell County, ILborders it2,72446.4%3.6 pCi/L+0.6 points
Sangamon County, ILborders it3,37843.7%3.7 pCi/L−2.1 points
McLean County, ILborders it4,54842.5%3.3 pCi/L−3.3 points
Macon County, ILborders it1,25138.8%3.1 pCi/L−7.0 points
Mason County, ILborders it4221.4%2.8 pCi/L−24.4 points
Where Logan County's reported results fell, 2017, beside Illinois and the United States
ResultLogan County testsLogan County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L2433.3%37.7%43.5%−4.4 points
2 to 4 pCi/L1520.8%28.6%24.8%−7.8 points
4 pCi/L and above3345.8%33.7%31.7%+12.1 points
Logan 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
Moultrie County25 of 704546.7%3.3 pCi/L
Rock Island County26 of 702,28346.5%3.7 pCi/L
Jersey County27 of 7012946.5%3.6 pCi/L
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
Logan County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
20177245.8%3.4 pCi/L18.2 pCi/L33.7%−8.5 points
201510554.3%4.5 pCi/L19.1 pCi/L36.6%−2.2 points
201413856.5%4.3 pCi/L17.7 pCi/L37.8%First on file

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

Logan County, Geology

The ground under Logan County

Predicted

USGS's geologic map puts all of Logan County's mapped land in one class: high radon potential. The map puts 84.1% of Logan County in the area it calls Galesburg Plain and 15.9% in Bloomington Ridged Plain. USGS gives both a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Logan County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Galesburg PlainIllinoian glacial deposits and loess over Paleozoic sedimentary rocks.High1384.1%
Bloomington Ridged PlainWisconsinan glacial deposits and loess over Paleozoic sedimentary rocks.High1315.9%

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

Logan County beside the ground around it

Logan 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; De Witt County comes nearest at 100%.

Share of land by USGS radon potential: Logan County, the 7 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Logan CountyZone 1NoneNone100%
Menard CountyZone 1NoneNone100%
De Witt CountyZone 1NoneNone100%
Macon CountyZone 1NoneNone100%
Mason CountyZone 1NoneNone100%
Sangamon CountyZone 1NoneNone100%
Tazewell CountyZone 1NoneNone100%
McLean 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

Logan County, Local resources

Radon testing and mitigation in Logan County

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

Logan County, Questions

Questions about radon in Logan County

Are radon levels high in Logan County?

In 2017, 45.8% of the radon tests reported to CDC for Logan 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, 29 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Logan County?

Logan County borders 7 counties: Menard County, De Witt County, Macon County, Mason County, Sangamon County, Tazewell County and McLean County.

Products

Logan County, Products

Testing a home in Logan County

In Logan County, 45.8% of 72 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Logan 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

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

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Logan County, Bordering counties

Counties bordering Logan County

Calculated by Radon411

Logan County, Cities and towns

Cities and towns in Logan County

About 27,182 people live in Logan County by the Census Bureau's estimate for July 1, 2025, 710 fewer than in 2020 (−2.5%). That works out to 44 people per square mile of land. Its largest town, Lincoln, has 12,981 residents, 47.8% of the total. Reported testing is thin here: 72 tests over 2017, or 2.6 for every 1,000 residents (2025 estimate), where Illinois as a whole comes to 10.9.

From Lincoln to Broadwell, CDC publishes no figure by town: each reads Logan County's.

The cities and towns in Logan County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Lincoln12,981−2.0%47.8%
Atlanta1,626−2.5%6.0%
Mount Pulaski1,499−2.2%5.5%
San Joseextends beyond Logan County460−4.2%Counted whole
Emden452−2.8%1.7%
Elkhart437−2.5%1.6%
Latham321−2.7%1.2%
Middletown317−1.9%1.2%
New Holland262−2.6%1.0%
Hartsburg255−2.3%0.9%
Broadwell138−2.1%0.5%

11 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 Logan County is counted whole, so it has no share.

Logan County, Homes

Homes in Logan County

Logan County is a place of houses on their own lots: 81% of its 11,984 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1964, close to Illinois' 1970: 44% date from before 1960 and 8% from 2000 or later. 69% 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 Logan County, Illinois, 2019 to 2023
HomesLogan CountyIllinois
Housing units11,9845,443,501
Detached houses81%58%
In buildings of 5 or more9%22%
Mobile homes3%2%
Built before 196044%38%
Built since 20008%16%
Middle year built19641970
Owner-occupied69%67%

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