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Radon Levels in Carroll County, Indiana

EPA puts Carroll County in Zone 1, its highest radon zone, and high results are common there: 60.5% of the 38 radon tests reported to CDC (2008 to 2017, laboratory totals) 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

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  • Share at 4+ pCi/L

    60.5%

    21.6 pts above IN

    Carroll
    60.5%
    Indiana
    38.9%

    38 tests, 2008 to 2017

  • Median result

    5.8pCi/L

    Action level reached

    Carroll
    5.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    38

    66th of 69 by tests

    Carroll
    38
    St. Joseph
    7,346

    Reported to CDC before any fix, 2008 to 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 Indiana

    4 of 69

    Top quarter

    Carroll
    60.5%
    Miami
    63.3%

    By share, of 69 with 30+ tests

Read a result for Carroll County

Starts at Carroll County's median, 5.8 pCi/L

5.8pCi/L

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

EPA’s reading of 5.8 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. Carroll County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Carroll County, At a glance

Carroll County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Carroll 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 Carroll County, 2008 to 2017, laboratory

Reported results by concentration band, Carroll County, 2008 to 2017, laboratory
Under 2 pCi/L: 21%2 to 4 pCi/L: 18%4 pCi/L and above: 61%

Of 38 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Carroll County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L821.1%
2 to 4 pCi/L718.4%
4 pCi/L and above2360.5%
What these figures count

These are the 38 tests reported to CDC for Carroll County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Carroll County, Compared

Carroll County radon figures, compared

Calculated by Radon411

More than half: 60.5% of the 38 radon tests reported to CDC for Carroll County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 4th of 69 Indiana counties with 30 or more tests for the same period. That is 21.6 points above the 38.9% pooled from 92 Indiana counties.

The median result, 5.8 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 54.0 pCi/L. The rest split 21.1% under 2 pCi/L and 18.4% from 2 to 4 (Indiana: 32.8% and 28.3%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 60.5% share point the same way here.

No bordering county with a figure for the same period reported a higher share; the closest is Howard County at 49.1%, the lowest Cass County at 34.1%. Statewide for the same period, Miami County reported the highest share (63.3%) and Jasper County the lowest (14.1%).

CDC's ten-year totals for Carroll County went from 44 tests (2005 to 2014) to 38 (2008 to 2017), the share going from 54.5% to 60.5%.

Nationally, every county with a figure for the same period pools to 35.7%; Carroll County sits 24.8 points above it.

Carroll County against Indiana, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Carroll County
Carroll County3860.5%5.8 pCi/LThis county
Indiana, pooled92 counties, pooled43,14838.9%Not pooled−21.6 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−24.8 points
Miami Countyhighest in the state3063.3%5.3 pCi/L+2.8 points
Jasper Countylowest in the state7114.1%1.2 pCi/L−46.4 points
Howard County, INborders it21649.1%3.8 pCi/L−11.4 points
Clinton County, INborders it8545.9%3.5 pCi/L−14.6 points
Tippecanoe County, INborders it1,21836.8%2.7 pCi/L−23.7 points
White County, INborders it4235.7%2.7 pCi/L−24.8 points
Cass County, INborders it9134.1%2.6 pCi/L−26.4 points
Where Carroll County's reported results fell, 2008 to 2017, laboratory, beside Indiana and the United States
ResultCarroll County testsCarroll County shareIndiana shareU.S. shareAgainst Indiana
Under 2 pCi/L821.1%32.8%39.6%−11.7 points
2 to 4 pCi/L718.4%28.3%24.7%−9.9 points
4 pCi/L and above2360.5%38.9%35.7%+21.6 points
Carroll County ranked among the 69 Indiana counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Miami County1 of 693063.3%5.3 pCi/L
Harrison County2 of 6922162.4%5.5 pCi/L
Benton County3 of 693461.8%5.7 pCi/L
Carroll County4 of 693860.5%5.8 pCi/L
Wabash County5 of 699159.3%5.8 pCi/L
Grant County6 of 697958.2%4.6 pCi/L
LaPorte County7 of 6979258.2%5.0 pCi/L
DeKalb County8 of 6924256.6%4.4 pCi/L
Wayne County9 of 6914056.4%4.5 pCi/L
Steuben County10 of 6914055.7%4.5 pCi/L
Delaware County11 of 6918755.1%4.2 pCi/L
Carroll County ten-year laboratory totals, against Indiana's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIndiana, pooledChange from the row before
2008 to 20173860.5%5.8 pCi/L54.0 pCi/L38.9%+4.1 points
2007 to 20163956.4%4.9 pCi/L54.0 pCi/L39.2%+4.1 points
2006 to 20154452.3%4.3 pCi/L54.0 pCi/L39.6%−2.2 points
2005 to 20144454.5%4.8 pCi/L54.0 pCi/L39.3%First on file

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

Carroll County, Geology

The ground under Carroll County

Predicted

USGS's geologic map puts all of Carroll County's mapped land in one class: high radon potential. All of it lies in the area the map calls Huron-Erie Lobe, to which USGS gives a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Carroll County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Huron-Erie LobeCalcareous clayey and loamy glacial deposits derived from marine carbonate and clastic 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.

Carroll County beside the ground around it

Carroll County has more high-potential ground than Indiana as a whole: 100% of its land against 56.6%. Of the 5 counties that border it, none has as large a share of high-potential ground; Clinton County comes nearest at 100%.

Share of land by USGS radon potential: Carroll County, the 5 counties bordering it and Indiana
AreaEPA zoneLow potentialModerate potentialHigh potential
Carroll CountyZone 1NoneNone100%
Cass CountyZone 1NoneNone100%
White CountyZone 1None0.7%99.3%
Tippecanoe CountyZone 1NoneNone100%
Clinton CountyZone 1NoneNone100%
Howard CountyZone 1NoneNone100%
Indiana92 counties, pooled by land areaVariesNone43.4%56.6%

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

Local help

Carroll County, Local resources

Radon testing and mitigation in Carroll County

What Indiana's program says
Phone
1-800-272-9723
Licensing of radon professionals
According to the Indiana Radon Rule, 410 IAC 5.1, everyone who is serving Indiana by doing radon testing, analysis and mitigation (radon reduction) in residential structures must be certified by the Indiana State Department of Health.

What it means

Carroll County, Questions

Questions about radon in Carroll County

Are radon levels high in Carroll County?

Over the 2008 to 2017 laboratory totals, 60.5% of the radon tests reported to CDC for Carroll County, Indiana were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.8 pCi/L. Of 69 Indiana counties with 30 or more tests for the same period, 3 reported a higher share; pooled, the state comes to 38.9%.

Which counties border Carroll County?

Carroll County borders 5 counties: Cass County, White County, Tippecanoe County, Clinton County and Howard County.

Products

Carroll County, Products

Testing a home in Carroll County

In Carroll County, 60.5% of 38 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 38.9% pooled across Indiana. In Zone 1 the year-round level in Carroll 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

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

Explore

Carroll County, Bordering counties

Counties bordering Carroll County

Calculated by Radon411

Carroll County, Cities and towns

Cities and towns in Carroll County

The Census Bureau estimates 20,655 residents in Carroll County for July 1, 2025, 316 more than in 2020 (+1.6%). That works out to 55 people per square mile of land. No town dominates: Delphi, the largest, has 2,973 residents, 14.4% of the total. Together its 5 incorporated places hold 30.7% of those residents; the other 69.3% live outside any of them. Reported testing is thin here: 38 tests over 2008 to 2017, or 1.8 for every 1,000 residents (2025 estimate), where Indiana as a whole comes to 6.2.

From Delphi to Yeoman, CDC publishes no figure by town: each reads Carroll County's.

The cities and towns in Carroll County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Delphi2,973+0.8%14.4%
Flora2,106−0.2%10.2%
Camden601+1.7%2.9%
Burlington533+1.7%2.6%
Yeoman122+1.7%0.6%

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).

Carroll County, Homes

Homes in Carroll County

Carroll County is a place of houses on their own lots: 85% of its 9,539 homes are detached single-family houses, against 73% across Indiana. The homes are older than Indiana's as a whole: half were built before 1965 (1976 for Indiana), and 45% date from before 1960. Owners live in 81% of the occupied homes (Indiana: 70%), so for most households a test and a fix are their own to order.

Homes in Carroll County, Indiana, 2019 to 2023
HomesCarroll CountyIndiana
Housing units9,5392,953,344
Detached houses85%73%
In buildings of 5 or more4%13%
Mobile homes6%4%
Built before 196045%32%
Built since 200015%21%
Middle year built19651976
Owner-occupied81%70%

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