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Radon Levels in Harrison County, Indiana

EPA puts Harrison County in Zone 1, its highest radon zone, and high results are common there: 62.4% of the 221 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

    62.4%

    23.5 pts above IN

    Harrison
    62.4%
    Indiana
    38.9%

    221 tests, 2008 to 2017

  • Median result

    5.5pCi/L

    Action level reached

    Harrison
    5.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    221

    27th of 69 by tests

    Harrison
    221
    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

    2 of 69

    Top quarter

    Harrison
    62.4%
    Miami
    63.3%

    By share, of 69 with 30+ tests

Read a result for Harrison County

Starts at Harrison County's median, 5.5 pCi/L

5.5pCi/L

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

EPA’s reading of 5.5 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. Harrison County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Harrison County, At a glance

Harrison County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Harrison 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: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Harrison County, 2008 to 2017, laboratory

Reported results by concentration band, Harrison County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 23%4 pCi/L and above: 62%

Of 221 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Harrison County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L3214.5%
2 to 4 pCi/L5123.1%
4 pCi/L and above13862.4%
What these figures count

These are the 221 tests reported to CDC for Harrison 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

Harrison County, Compared

Harrison County radon figures, compared

Calculated by Radon411

More than half: 62.4% of the 221 radon tests reported to CDC for Harrison County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 2nd of 69 Indiana counties with 30 or more tests for the same period. That is 23.5 points above the 38.9% pooled from 92 Indiana counties.

The median result, 5.5 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 119.2 pCi/L. The rest split 14.5% under 2 pCi/L and 23.1% from 2 to 4 (Indiana: 32.8% and 28.3%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 62.4% share point the same way here.

1 of its 5 bordering counties with figures ran higher, led by Meade County, KY at 68.4%; Jefferson County, KY reported 39.4%. 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 Harrison County went from 167 tests (2005 to 2014) to 221 (2008 to 2017), the share going from 68.3% to 62.4%.

Nationally, every county with a figure for the same period pools to 35.7%; Harrison County sits 26.7 points above it. CDC also counts 14 tests taken after mitigation in Harrison County for the same period: tests in homes where a fix was already in.

Harrison County against Indiana, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Harrison County
Harrison County22162.4%5.5 pCi/LThis county
Indiana, pooled92 counties, pooled43,14838.9%Not pooled−23.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−26.7 points
Miami Countyhighest in the state3063.3%5.3 pCi/L+0.9 points
Jasper Countylowest in the state7114.1%1.2 pCi/L−48.3 points
Meade County, KYborders it11768.4%8.2 pCi/L+6.0 points
Hardin County, KYborders it42950.3%4.0 pCi/L−12.1 points
Floyd County, INborders it31642.4%3.3 pCi/L−20.0 points
Washington County, INborders it3842.1%3.5 pCi/L−20.3 points
Jefferson County, KYborders it6,59039.4%2.7 pCi/L−23.0 points
Crawford County, INborders it1030.0%2.7 pCi/L−32.4 points
Where Harrison County's reported results fell, 2008 to 2017, laboratory, beside Indiana and the United States
ResultHarrison County testsHarrison County shareIndiana shareU.S. shareAgainst Indiana
Under 2 pCi/L3214.5%32.8%39.6%−18.3 points
2 to 4 pCi/L5123.1%28.3%24.7%−5.2 points
4 pCi/L and above13862.4%38.9%35.7%+23.5 points
Harrison 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
Harrison County ten-year laboratory totals, against Indiana's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIndiana, pooledChange from the row before
2008 to 201722162.4%5.5 pCi/L119.2 pCi/L38.9%−0.2 points
2007 to 201619062.6%6.0 pCi/L119.2 pCi/L39.2%−4.6 points
2006 to 201518367.2%6.2 pCi/L119.2 pCi/L39.6%−1.1 points
2005 to 201416768.3%6.3 pCi/L119.2 pCi/L39.3%First on file

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

Harrison County, Geology

The ground under Harrison County

Predicted

USGS's geologic map puts all of Harrison County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Crawford Upland/Mitchell Plain/Norman Upland, to which USGS gives a radon index of 11, in the moderate band (9 to 11).

USGS's geologic areas under Harrison County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Crawford Upland/Mitchell Plain/Norman UplandUnglaciated, underlain by karsted Mississippian carbonate rocks.Moderate1199.9%

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

Harrison County beside the ground around it

Across Indiana 56.6% of the land is rated high; none of Harrison County's is. Of the 6 counties that border it, 3 have more high-potential ground, Jefferson County, KY the most at 55.1%.

Share of land by USGS radon potential: Harrison County, the 6 counties bordering it and Indiana
AreaEPA zoneLow potentialModerate potentialHigh potential
Harrison CountyZone 1None100%None
Floyd CountyZone 2None95.7%4.3%
Meade County, KYZone 2None100%None
Crawford CountyZone 2None100%None
Jefferson County, KYZone 1None44.9%55.1%
Washington CountyZone 1None100%None
Hardin County, KYZone 2None96.6%3.4%
Indiana92 counties, pooled by land areaVariesNone43.4%56.6%

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

Local help

Harrison County, Local resources

Radon testing and mitigation in Harrison 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

Harrison County, Questions

Questions about radon in Harrison County

Are radon levels high in Harrison County?

Over the 2008 to 2017 laboratory totals, 62.4% of the radon tests reported to CDC for Harrison County, Indiana were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.5 pCi/L. Of 69 Indiana counties with 30 or more tests for the same period, 1 reported a higher share; pooled, the state comes to 38.9%.

Which counties border Harrison County?

Harrison County borders 6 counties: Floyd County, IN, Meade County, KY, Crawford County, IN, Jefferson County, KY, Washington County, IN and Hardin County, KY.

Products

Harrison County, Products

Testing a home in Harrison County

In Harrison County, 62.4% of 221 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 Harrison 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

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

Explore

Harrison County, Bordering counties

Counties bordering Harrison County

Calculated by Radon411

Harrison County, Cities and towns

Cities and towns in Harrison County

The Census Bureau estimates 40,437 residents in Harrison County for July 1, 2025, 764 more than in 2020 (+1.9%). That works out to 84 people per square mile of land. No town dominates: Corydon, the largest, has 3,196 residents, 7.9% of the total. CDC's 221 reported tests for 2008 to 2017 work out to 5.5 per 1,000 residents (2025 estimate), close to Indiana's 6.2.

From Corydon to New Amsterdam, CDC publishes no figure by town: each reads Harrison County's.

The cities and towns in Harrison County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Corydon3,196+0.7%7.9%
Lanesville947+1.2%2.3%
Palmyra913+1.6%2.3%
Milltownextends beyond Harrison County807+2.5%Counted whole
Elizabeth207+1.0%0.5%
Crandall135+1.5%0.3%
New Middletown90Level0.2%
Laconia75Level0.2%
Mauckport45Level0.1%
New Amsterdam13LevelUnder 0.1%

10 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 Harrison County is counted whole, so it has no share.

Harrison County, Homes

Homes in Harrison County

Harrison County is a place of houses on their own lots: 79% of its 16,842 homes are detached single-family houses, against 73% across Indiana. Much of Harrison County is recent building: 25% of its homes have gone up since 2000 and the middle year built is 1987, against 1976 for Indiana. Owners live in 84% of the occupied homes (Indiana: 70%), so for most households a test and a fix are their own to order.

Homes in Harrison County, Indiana, 2019 to 2023
HomesHarrison CountyIndiana
Housing units16,8422,953,344
Detached houses79%73%
In buildings of 5 or more5%13%
Mobile homes12%4%
Built before 196023%32%
Built since 200025%21%
Middle year built19871976
Owner-occupied84%70%

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