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Radon Levels in Adams County, Indiana

EPA puts Adams County in Zone 1, its highest radon zone, and high results are common there: 48.5% of the 66 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

    48.5%

    9.6 pts above IN

    Adams
    48.5%
    Indiana
    38.9%

    66 tests, 2008 to 2017

  • Median result

    3.8pCi/L

    Below action level

    Adams
    3.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    66

    57th of 69 by tests

    Adams
    66
    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

    22 of 69

    Middle half

    Adams
    48.5%
    Miami
    63.3%

    By share, of 69 with 30+ tests

Read a result for Adams County

Starts at Adams County's median, 3.8 pCi/L

3.8pCi/L

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

EPA’s reading of 3.8 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. Adams County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Adams County, At a glance

Adams County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Adams County, 2008 to 2017, laboratory
Under 2 pCi/L: 27%2 to 4 pCi/L: 24%4 pCi/L and above: 49%

Of 66 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Adams County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1827.3%
2 to 4 pCi/L1624.2%
4 pCi/L and above3248.5%
What these figures count

These are the 66 tests reported to CDC for Adams 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

Adams County, Compared

Adams County radon figures, compared

Calculated by Radon411

In Adams County, about 5 in 10 reported tests over the 2008 to 2017 laboratory totals (32 of 66) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 12.8 points higher. Across 92 Indiana counties pooled together, 38.9% of tests reached that level, so Adams County runs 9.6 points above its state.

Of 3 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 41.8% (Allen County) to 57.7% (Mercer County, OH). By share, Adams County is 22nd of 69 Indiana counties with 30 or more tests for the same period.

Half the tests came in under 3.8 pCi/L and half over it; the single highest reached 55.8 pCi/L. Below the action level, 18 tests (27.3%) came in under 2 pCi/L, against 32.8% statewide, and 16 tests (24.2%) fell between 2 and 4, against 28.3% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 48.5% share point the same way here. USGS geology rates 100% of the county's land high radon potential. CDC also counts 16 tests taken after mitigation in Adams County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Adams County went from 54 tests (2005 to 2014) to 66 (2008 to 2017), the share going from 51.9% to 48.5%.

Adams County against Indiana, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Adams County
Adams County6648.5%3.8 pCi/LThis county
Indiana, pooled92 counties, pooled43,14838.9%Not pooled−9.6 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−12.8 points
Miami Countyhighest in the state3063.3%5.3 pCi/L+14.8 points
Jasper Countylowest in the state7114.1%1.2 pCi/L−34.4 points
Mercer County, OHborders it14957.7%5.1 pCi/L+9.2 points
Van Wert County, OHborders it2653.8%4.3 pCi/L+5.3 points
Wells County, INborders it16147.8%3.6 pCi/L−0.7 points
Jay County, INborders it944.4%2.7 pCi/L−4.1 points
Allen County, INborders it3,99041.8%3.3 pCi/L−6.7 points
Where Adams County's reported results fell, 2008 to 2017, laboratory, beside Indiana and the United States
ResultAdams County testsAdams County shareIndiana shareU.S. shareAgainst Indiana
Under 2 pCi/L1827.3%32.8%39.6%−5.5 points
2 to 4 pCi/L1624.2%28.3%24.7%−4.1 points
4 pCi/L and above3248.5%38.9%35.7%+9.6 points
Adams 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
Shelby County17 of 698450.0%4.0 pCi/L
Tipton County18 of 696949.3%3.9 pCi/L
Howard County19 of 6921649.1%3.8 pCi/L
Madison County20 of 6923949.0%3.8 pCi/L
Bartholomew County21 of 691,70748.7%3.9 pCi/L
Adams County22 of 696648.5%3.8 pCi/L
Wells County23 of 6916147.8%3.6 pCi/L
Clark County24 of 6951247.7%3.6 pCi/L
Porter County25 of 691,13646.5%3.5 pCi/L
Fulton County26 of 699746.4%3.3 pCi/L
Elkhart County27 of 692,85646.4%3.7 pCi/L
Adams County ten-year laboratory totals, against Indiana's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIndiana, pooledChange from the row before
2008 to 20176648.5%3.8 pCi/L55.8 pCi/L38.9%−2.3 points
2007 to 20166150.8%4.1 pCi/L55.8 pCi/L39.2%+0.8 points
2006 to 20155850.0%4.0 pCi/L55.8 pCi/L39.6%−1.9 points
2005 to 20145451.9%4.2 pCi/L55.8 pCi/L39.3%First on file

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

Adams County, Geology

The ground under Adams County

Predicted

USGS's geologic map puts all of Adams 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 Adams 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.High1399.9%

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

Adams County beside the ground around it

Adams 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; Jay County comes nearest at 100%.

Share of land by USGS radon potential: Adams County, the 5 counties bordering it and Indiana
AreaEPA zoneLow potentialModerate potentialHigh potential
Adams CountyZone 1NoneNone100%
Wells CountyZone 1NoneNone100%
Van Wert County, OHZone 1None0.1%99.9%
Allen CountyZone 1NoneNone100%
Jay CountyZone 1NoneNone100%
Mercer County, OHZone 1NoneNone100%
Indiana92 counties, pooled by land areaVariesNone43.4%56.6%

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

Local help

Adams County, Local resources

Radon testing and mitigation in Adams 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

Adams County, Questions

Questions about radon in Adams County

Are radon levels high in Adams County?

Over the 2008 to 2017 laboratory totals, 48.5% of the radon tests reported to CDC for Adams County, Indiana were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.8 pCi/L. Of 69 Indiana counties with 30 or more tests for the same period, 21 reported a higher share; pooled, the state comes to 38.9%.

Which counties border Adams County?

Adams County borders 5 counties: Wells County, IN, Van Wert County, OH, Allen County, IN, Jay County, IN and Mercer County, OH.

Products

Adams County, Products

Testing a home in Adams County

In Adams County, 48.5% of 66 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 Adams 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

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

Explore

Adams County, Bordering counties

Counties bordering Adams County

Calculated by Radon411

Adams County, Cities and towns

Cities and towns in Adams County

The Census Bureau estimates 36,650 residents in Adams County for July 1, 2025, 798 more than in 2020 (+2.2%). That works out to 108 people per square mile of land. Its largest town, Decatur, has 10,090 residents, 27.5% of the total. Together its 4 incorporated places hold 45.2% of those residents; the other 54.8% live outside any of them. Reported testing is thin here: 66 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 Decatur to Monroe, CDC publishes no figure by town: each reads Adams County's.

The cities and towns in Adams County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Decatur10,090+1.6%27.5%
Berne4,286+2.5%11.7%
Geneva1,293+2.6%3.5%
Monroe901+2.2%2.5%

4 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).

Adams County, Homes

Homes in Adams County

Adams County is a place of houses on their own lots: 84% of its 13,250 homes are detached single-family houses, against 73% across Indiana. Half of its homes were built before 1970, close to Indiana's 1976: 40% date from before 1960 and 14% from 2000 or later. Owners live in 82% of the occupied homes (Indiana: 70%), so for most households a test and a fix are their own to order.

Homes in Adams County, Indiana, 2019 to 2023
HomesAdams CountyIndiana
Housing units13,2502,953,344
Detached houses84%73%
In buildings of 5 or more8%13%
Mobile homes1%4%
Built before 196040%32%
Built since 200014%21%
Middle year built19701976
Owner-occupied82%70%

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