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Radon Levels in Montgomery County, Iowa

EPA puts Montgomery County in Zone 1, its highest radon zone, and high results are common there: 67.4% of the 233 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

    67.4%

    8.9 pts above IA

    Montgomery
    67.4%
    Iowa
    58.5%

    233 tests, 2008 to 2017

  • Median result

    6.1pCi/L

    Action level reached

    Montgomery
    6.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    233

    79th of 99 by tests

    Montgomery
    233
    Polk
    10,945

    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 Iowa

    41 of 99

    Middle half

    Montgomery
    67.4%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Montgomery County

Starts at Montgomery County's median, 6.1 pCi/L

6.1pCi/L

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

EPA’s reading of 6.1 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. Montgomery County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Montgomery County, At a glance

Montgomery County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Montgomery County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 18%4 pCi/L and above: 67%

Of 233 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Montgomery County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L3515.0%
2 to 4 pCi/L4117.6%
4 pCi/L and above15767.4%
What these figures count

These are the 233 tests reported to CDC for Montgomery 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

Montgomery County, Compared

Montgomery County radon figures, compared

Calculated by Radon411

More than half: 67.4% of the 233 radon tests reported to CDC for Montgomery County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 41st of 99 Iowa counties with 30 or more tests for the same period. That is 8.9 points above the 58.5% pooled from 99 Iowa counties.

The median result, 6.1 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 60.6 pCi/L. The rest split 15.0% under 2 pCi/L and 17.6% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 67.4% share point the same way here.

4 of its 7 bordering counties with figures ran higher, led by Cass County at 77.4%; Pottawattamie County reported 57.4%. Statewide for the same period, Sioux County reported the highest share (84.2%) and Decatur County the lowest (25.9%).

CDC's ten-year totals for Montgomery County went from 194 tests (2005 to 2014) to 233 (2008 to 2017), the share going from 65.5% to 67.4%.

Nationally, every county with a figure for the same period pools to 35.7%; Montgomery County sits 31.7 points above it. CDC also counts 26 tests taken after mitigation in Montgomery County for the same period: tests in homes where a fix was already in.

Montgomery County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Montgomery County
Montgomery County23367.4%6.1 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−8.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−31.7 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+16.8 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−41.5 points
Cass County, IAborders it32777.4%8.1 pCi/L+10.0 points
Page County, IAborders it65371.7%7.2 pCi/L+4.3 points
Mills County, IAborders it46570.1%6.1 pCi/L+2.7 points
Fremont County, IAborders it20569.8%7.2 pCi/L+2.4 points
Adams County, IAborders it8165.4%6.1 pCi/L−2.0 points
Taylor County, IAborders it23560.9%4.6 pCi/L−6.5 points
Pottawattamie County, IAborders it1,86857.4%4.7 pCi/L−10.0 points
Where Montgomery County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultMontgomery County testsMontgomery County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L3515.0%21.8%39.6%−6.8 points
2 to 4 pCi/L4117.6%19.7%24.7%−2.1 points
4 pCi/L and above15767.4%58.5%35.7%+8.9 points
Montgomery County ranked among the 99 Iowa counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Woodbury County36 of 993,54169.2%6.1 pCi/L
Pocahontas County37 of 9941768.8%6.4 pCi/L
Boone County38 of 991,13468.7%6.0 pCi/L
Tama County39 of 9933367.9%7.0 pCi/L
Worth County40 of 9915467.5%6.0 pCi/L
Montgomery County41 of 9923367.4%6.1 pCi/L
Marion County42 of 991,15167.3%6.0 pCi/L
Osceola County43 of 9912267.2%6.8 pCi/L
Grundy County44 of 9950166.9%6.9 pCi/L
Wright County45 of 9929266.8%6.2 pCi/L
Winneshiek County46 of 991,07166.4%6.2 pCi/L
Montgomery County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201723367.4%6.1 pCi/L60.6 pCi/L58.5%−1.5 points
2007 to 201623568.9%6.3 pCi/L80.0 pCi/L58.6%+1.3 points
2006 to 201521367.6%6.1 pCi/L80.0 pCi/L59.4%+2.1 points
2005 to 201419465.5%6.0 pCi/L80.0 pCi/L59.6%First on file

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

Montgomery County, Geology

The ground under Montgomery County

Predicted

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

USGS's geologic areas under Montgomery County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High13100%

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

Montgomery County beside the ground around it

On high-potential ground Montgomery County is close to Iowa as a whole: 100% of its land against 98.8%. Of the 7 counties that border it, none has as large a share of high-potential ground; Adams County comes nearest at 100%.

Share of land by USGS radon potential: Montgomery County, the 7 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Montgomery CountyZone 1NoneNone100%
Page CountyZone 1NoneNone100%
Adams CountyZone 1NoneNone100%
Mills CountyZone 1NoneNone100%
Taylor CountyZone 1NoneNone100%
Pottawattamie CountyZone 1NoneNone100%
Cass CountyZone 1NoneNone100%
Fremont CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Montgomery County, Local resources

Radon testing and mitigation in Montgomery County

What Iowa's program says
Phone
(515) 281-4928
Licensing of radon professionals
Iowa’s radon program approves applications for persons who wish to become certified to perform radon testing or credentialed to perform mitigation and laboratories that provide radon testing devices and analytical services.
Disclosure when a home is sold or rented
However, per Iowa Code chapters 543B.9 and 543B.18 and Iowa Administrative Code 193E Chapter 14 administered by the Iowa Real Estate Commission, a seller must disclose any known tests for the presence of radon and if yes, provide the date of last report and the result(s).

What it means

Montgomery County, Questions

Questions about radon in Montgomery County

Are radon levels high in Montgomery County?

Over the 2008 to 2017 laboratory totals, 67.4% of the radon tests reported to CDC for Montgomery County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 6.1 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 40 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Montgomery County?

Montgomery County borders 7 counties: Page County, Adams County, Mills County, Taylor County, Pottawattamie County, Cass County and Fremont County.

Products

Montgomery County, Products

Testing a home in Montgomery County

In Montgomery County, 67.4% of 233 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 58.5% pooled across Iowa. In Zone 1 the year-round level in Montgomery 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

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

Explore

Montgomery County, Bordering counties

Counties bordering Montgomery County

Calculated by Radon411

Montgomery County, Cities and towns

Cities and towns in Montgomery County

About 10,002 people live in Montgomery County by the Census Bureau's estimate for July 1, 2025, 332 fewer than in 2020 (−3.2%). That works out to 24 people per square mile of land. Red Oak alone is home to 5,388 of them, 53.9% of the total. Together its 6 incorporated places hold 75.9% of those residents; the other 24.1% live outside any of them. CDC's 233 reported tests for 2008 to 2017 work out to 23.3 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Red Oak to Coburg, CDC publishes no figure by town: each reads Montgomery County's.

The cities and towns in Montgomery County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Red Oak5,388−3.7%53.9%
Villisca1,099−2.9%11.0%
Stanton664−0.7%6.6%
Elliott325−4.1%3.2%
Grant83−3.5%0.8%
Coburg29+3.6%0.3%

6 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).

Montgomery County, Homes

Homes in Montgomery County

Montgomery County is a place of houses on their own lots: 84% of its 5,011 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1955 (1971 for Iowa), and 54% date from before 1960. 72% of occupied homes are lived in by their owner (Iowa: 72%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Montgomery County, Iowa, 2019 to 2023
HomesMontgomery CountyIowa
Housing units5,0111,427,175
Detached houses84%72%
In buildings of 5 or more5%14%
Mobile homes3%3%
Built before 196054%39%
Built since 20009%21%
Middle year built19551971
Owner-occupied72%72%

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