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Radon Levels in Richland County, Illinois

EPA puts Richland County in Zone 2, its middle radon zone, and only 21 radon tests from it are on file with CDC (2017). 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

    18.9%

    24.2 pts below IL

    Richland
    18.9%
    Illinois
    43.1%

    148 tests, 2008 to 2017

  • Median result

    1.8pCi/L

    Below action level

    Richland
    1.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    148

    62nd of 93 by tests

    Richland
    148
    Cook
    14,199

    Reported to CDC before any fix, 2008 to 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

    87 of 93

    Lowest quarter

    Richland
    18.9%
    Stark
    80.5%

    By share, of 93 with 30+ tests

Read a result for Richland County

Starts at Richland County's median, 1.8 pCi/L

1.8pCi/L

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

EPA’s reading of 1.8 pCi/L

Below 2 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 below 2 pCi/L, the level at which EPA says a fix should be considered. Richland County's median reported result, 2008 to 2017.

Interpret this reading

The data

Richland County, At a glance

Richland County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Richland 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: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Richland County, 2017

Share of reported tests at or above 4 pCi/L, by year, Richland County
Share of reported tests at or above 4 pCi/L, by year, Richland County
YearShare of reported tests at or above 4 pCi/L
201423.1%
201714.3%

2017: 14.3%. Across these years the share ran from 14.3% to 23.1%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 21 tests were reported to CDC for Richland County over 2017, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor 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

Richland County, Compared

Richland County radon figures, compared

Calculated by Radon411

Richland County's 148 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.8 pCi/L and a maximum of 20.7 pCi/L, and 18.9% reached 4 pCi/L. Illinois as a whole (102 Illinois counties, pooled) comes to 43.1%: 24.2 points higher than here.

The newest figure, in 2017, counts only 21 tests (14.3% at or above 4 pCi/L), too few to compare, so this reading uses the 148-test figure.

Among its state's counties it ranks 87th of 93 Illinois counties with 30 or more tests for the same period. Statewide for the same period, Stark County reported the highest share (80.5%) and Williamson County the lowest (13.3%).

Below the action level, 79 tests (53.4%) came in under 2 pCi/L, against 31.6% statewide, and 41 tests (27.7%) fell between 2 and 4, against 25.3% statewide. The busiest year on file was 2014, with 78 tests reported; the quietest, 2017, had 21.

EPA's 1993 zone map puts Richland County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.

Next door, the shares run from 14.7% in Clay County to 32.4% in Wabash County, with Lawrence County, Wayne County and Clay County below Richland County.

Richland County against Illinois, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Richland County
Richland County14818.9%1.8 pCi/LThis county
Illinois, pooled102 counties, pooled108,90943.1%Not pooled+24.2 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+16.8 points
Stark Countyhighest in the state8780.5%7.4 pCi/L+61.6 points
Williamson Countylowest in the state60113.3%1.3 pCi/L−5.6 points
Wabash County, ILborders it3432.4%3.0 pCi/L+13.5 points
Jasper County, ILborders it7623.7%1.9 pCi/L+4.8 points
Edwards County, ILborders it1921.1%2.1 pCi/L+2.2 points
Crawford County, ILborders it18119.3%1.8 pCi/L+0.4 points
Lawrence County, ILborders it4818.8%1.8 pCi/L−0.1 points
Wayne County, ILborders it8615.1%1.4 pCi/L−3.8 points
Clay County, ILborders it6814.7%1.1 pCi/L−4.2 points
Where Richland County's reported results fell, 2008 to 2017, laboratory, beside Illinois and the United States
ResultRichland County testsRichland County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L7953.4%31.6%39.6%+21.8 points
2 to 4 pCi/L4127.7%25.3%24.7%+2.4 points
4 pCi/L and above2818.9%43.1%35.7%−24.2 points
Richland County ranked among the 93 Illinois counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Saline County82 of 938220.7%1.7 pCi/L
Marion County83 of 9336420.6%1.7 pCi/L
Cook County84 of 9314,19920.2%1.8 pCi/L
Franklin County85 of 9319919.6%1.8 pCi/L
Crawford County86 of 9318119.3%1.8 pCi/L
Richland County87 of 9314818.9%1.8 pCi/L
Lawrence County88 of 934818.8%1.8 pCi/L
Massac County89 of 933315.2%1.9 pCi/L
Wayne County90 of 938615.1%1.4 pCi/L
Clay County91 of 936814.7%1.1 pCi/L
Johnson County92 of 934814.6%1.8 pCi/L
Richland County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
20172114.3%1.0 pCi/L11.1 pCi/L33.7%−8.8 points
20147823.1%1.7 pCi/L4.7 pCi/L37.8%First on file

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

Richland County, Geology

The ground under Richland County

Predicted

USGS's geologic map puts all of Richland County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Southern Central Lowland Province, to which USGS gives a radon index of 9, in the moderate band (9 to 11).

USGS's geologic areas under Richland County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Southern Central Lowland ProvinceIllinoian glacial deposits, sandstone, and gray shale.Moderate9100%

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

Richland County beside the ground around it

Across Illinois 64.5% of the land is rated high; none of Richland County's is. Of the 7 counties that border it, none has as large a share of moderate-potential ground; Clay County comes nearest at 100%.

Share of land by USGS radon potential: Richland County, the 7 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Richland CountyZone 2None100%None
Edwards CountyZone 2None100%None
Lawrence CountyZone 2None100%None
Clay CountyZone 2None100%None
Wabash CountyZone 2None100%None
Jasper CountyZone 2None100%None
Crawford CountyZone 2None100%None
Wayne CountyZone 2None100%None
Illinois102 counties, pooled by land areaVaries0.9%34.5%64.5%

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

Local help

Richland County, Local resources

Radon testing and mitigation in Richland 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

Richland County, Questions

Questions about radon in Richland County

Are radon levels high in Richland County?

In 2017, 14.3% of the radon tests reported to CDC for Richland County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.0 pCi/L. Of 93 Illinois counties with 30 or more tests for the same period, 86 reported a higher share; pooled, the state comes to 43.1%.

Which counties border Richland County?

Richland County borders 7 counties: Edwards County, Lawrence County, Clay County, Wabash County, Jasper County, Crawford County and Wayne County.

Products

Richland County, Products

Testing a home in Richland County

In Richland County, 18.9% of 148 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 43.1% pooled across Illinois. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Richland County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Richland County homes, compared

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Richland County, Bordering counties

Counties bordering Richland County

Calculated by Radon411

Richland County, Cities and towns

Cities and towns in Richland County

About 15,219 people live in Richland County by the Census Bureau's estimate for July 1, 2025, 589 fewer than in 2020 (−3.7%). That works out to 42 people per square mile of land. Olney alone is home to 8,347 of them, 54.8% of the total. Together its 5 incorporated places hold 62.1% of those residents; the other 37.9% live outside any of them. CDC's 148 reported tests for 2008 to 2017 work out to 9.7 per 1,000 residents (2025 estimate), close to Illinois' 8.6.

From Olney to Calhoun, CDC publishes no figure by town: each reads Richland County's.

The cities and towns in Richland County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Olney8,347−4.0%54.8%
Noble609−3.5%4.0%
Parkersburg184−1.6%1.2%
Claremont158−3.1%1.0%
Calhoun153−3.8%1.0%

5 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).

Richland County, Homes

Homes in Richland County

Richland County is a place of houses on their own lots: 79% of its 7,366 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1973, close to Illinois' 1970: 35% date from before 1960 and 14% from 2000 or later. 74% 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 Richland County, Illinois, 2019 to 2023
HomesRichland CountyIllinois
Housing units7,3665,443,501
Detached houses79%58%
In buildings of 5 or more4%22%
Mobile homes13%2%
Built before 196035%38%
Built since 200014%16%
Middle year built19731970
Owner-occupied74%67%

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