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Radon Levels in Floyd County, Iowa

EPA puts Floyd County in Zone 1, its highest radon zone, and high results are common there: 59.5% of the 697 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

    59.5%

    1.0 pts above IA

    Floyd
    59.5%
    Iowa
    58.5%

    697 tests, 2008 to 2017

  • Median result

    5.1pCi/L

    Action level reached

    Floyd
    5.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    697

    33rd of 99 by tests

    Floyd
    697
    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

    66 of 99

    Middle half

    Floyd
    59.5%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Floyd County

Starts at Floyd County's median, 5.1 pCi/L

5.1pCi/L

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

EPA’s reading of 5.1 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. Floyd County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Floyd County, At a glance

Floyd County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Floyd County, 2008 to 2017, laboratory
Under 2 pCi/L: 19%2 to 4 pCi/L: 22%4 pCi/L and above: 59%

Of 697 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Floyd County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L12918.5%
2 to 4 pCi/L15322.0%
4 pCi/L and above41559.5%
What these figures count

These are the 697 tests reported to CDC for Floyd 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

Floyd County, Compared

Floyd County radon figures, compared

Calculated by Radon411

More than half: 59.5% of the 697 radon tests reported to CDC for Floyd County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 66th of 99 Iowa counties with 30 or more tests for the same period. That is 1.0 points above the 58.5% pooled from 99 Iowa counties.

The median result, 5.1 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 133.5 pCi/L. The rest split 18.5% under 2 pCi/L and 22.0% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 59.5% share point the same way here.

4 of its 7 bordering counties with figures ran higher, led by Franklin County at 73.5%; Bremer County reported 53.0%. 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 Floyd County went from 607 tests (2005 to 2014) to 697 (2008 to 2017), the share going from 62.3% to 59.5%.

Nationally, every county with a figure for the same period pools to 35.7%; Floyd County sits 23.8 points above it. CDC also counts 72 tests taken after mitigation in Floyd County for the same period: tests in homes where a fix was already in.

Floyd County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Floyd County
Floyd County69759.5%5.1 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−1.0 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−23.8 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+24.7 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−33.6 points
Franklin County, IAborders it31373.5%6.2 pCi/L+14.0 points
Mitchell County, IAborders it44470.7%6.4 pCi/L+11.2 points
Howard County, IAborders it38861.3%5.9 pCi/L+1.8 points
Butler County, IAborders it37759.9%5.2 pCi/L+0.4 points
Cerro Gordo County, IAborders it1,66259.0%4.8 pCi/L−0.5 points
Chickasaw County, IAborders it49859.0%4.9 pCi/L−0.5 points
Bremer County, IAborders it95753.0%4.3 pCi/L−6.5 points
Where Floyd County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultFloyd County testsFloyd County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L12918.5%21.8%39.6%−3.3 points
2 to 4 pCi/L15322.0%19.7%24.7%+2.3 points
4 pCi/L and above41559.5%58.5%35.7%+1.0 points
Floyd 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
Taylor County61 of 9923560.9%4.6 pCi/L
Cedar County62 of 9976560.4%5.0 pCi/L
Keokuk County63 of 9921460.3%5.2 pCi/L
Butler County64 of 9937759.9%5.2 pCi/L
Story County65 of 992,56859.9%5.0 pCi/L
Floyd County66 of 9969759.5%5.1 pCi/L
Jones County67 of 9955559.3%5.1 pCi/L
Iowa County68 of 9951959.2%5.1 pCi/L
Chickasaw County69 of 9949859.0%4.9 pCi/L
Cerro Gordo County70 of 991,66259.0%4.8 pCi/L
Dallas County71 of 992,35258.5%4.9 pCi/L
Floyd County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201769759.5%5.1 pCi/L133.5 pCi/L58.5%−0.5 points
2007 to 201668860.0%5.1 pCi/L133.5 pCi/L58.6%−1.4 points
2006 to 201564261.4%5.2 pCi/L133.5 pCi/L59.4%−0.9 points
2005 to 201460762.3%5.2 pCi/L133.5 pCi/L59.6%First on file

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

Floyd County, Geology

The ground under Floyd County

Predicted

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

USGS's geologic areas under Floyd County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Iowan SurfacePre-Illinoian glaical deposits and loess.High12100%

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

Floyd County beside the ground around it

On high-potential ground Floyd 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; Bremer County comes nearest at 100%.

Share of land by USGS radon potential: Floyd County, the 7 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Floyd CountyZone 1NoneNone100%
Butler CountyZone 1NoneNone100%
Mitchell CountyZone 1NoneNone100%
Cerro Gordo CountyZone 1NoneNone100%
Chickasaw CountyZone 1NoneNone100%
Bremer CountyZone 1NoneNone100%
Howard CountyZone 1NoneNone100%
Franklin CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Floyd County, Local resources

Radon testing and mitigation in Floyd 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

Floyd County, Questions

Questions about radon in Floyd County

Are radon levels high in Floyd County?

Over the 2008 to 2017 laboratory totals, 59.5% of the radon tests reported to CDC for Floyd County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.1 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 65 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Floyd County?

Floyd County borders 7 counties: Butler County, Mitchell County, Cerro Gordo County, Chickasaw County, Bremer County, Howard County and Franklin County.

Products

Floyd County, Products

Testing a home in Floyd County

In Floyd County, 59.5% of 697 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 Floyd 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

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

Explore

Floyd County, Bordering counties

Counties bordering Floyd County

Calculated by Radon411

Floyd County, Cities and towns

Cities and towns in Floyd County

About 14,901 people live in Floyd County by the Census Bureau's estimate for July 1, 2025, 694 fewer than in 2020 (−4.5%). That works out to 30 people per square mile of land. Its largest town, Charles City, has 7,013 residents, 47.1% of the total. Testing is reported here more often than across the state: CDC's 697 reported tests for 2008 to 2017 come to 46.8 for every 1,000 residents (2025 estimate), against 29.4 for Iowa.

From Charles City to Colwell, CDC publishes no figure by town: each reads Floyd County's.

The cities and towns in Floyd County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Charles City7,013−5.0%47.1%
Nashuaextends beyond Floyd County1,505−3.0%Counted whole
Nora Springsextends beyond Floyd County1,316−3.6%Counted whole
Greeneextends beyond Floyd County939−5.6%Counted whole
Rockford715−5.8%4.8%
Rudd336−5.9%2.3%
Floyd294−4.9%2.0%
Marble Rock255−5.2%1.7%
Colwell53−5.4%0.4%

9 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 Floyd County is counted whole, so it has no share.

Floyd County, Homes

Homes in Floyd County

Floyd County is a place of houses on their own lots: 83% of its 7,308 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1960 (1971 for Iowa), and 51% date from before 1960. 74% 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 Floyd County, Iowa, 2019 to 2023
HomesFloyd CountyIowa
Housing units7,3081,427,175
Detached houses83%72%
In buildings of 5 or more9%14%
Mobile homes1%3%
Built before 196051%39%
Built since 200010%21%
Middle year built19601971
Owner-occupied74%72%

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