Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Hardin County, Iowa
EPA puts Hardin County in Zone 1, its highest radon zone, and high results are common there: 62.8% of the 349 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
Share at 4+ pCi/L
62.8%
4.3 pts above IA
- Hardin
- 62.8%
- Iowa
- 58.5%
349 tests, 2008 to 2017
Median result
5.6pCi/L
Action level reached
- Hardin
- 5.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
349
66th of 99 by tests
- Hardin
- 349
- Polk
- 10,945
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Iowa
53 of 99
Middle half
- Hardin
- 62.8%
- Sioux
- 84.2%
By share, of 99 with 30+ tests
Read a result for Hardin County
Starts at Hardin County's median, 5.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 5.6 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 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. Hardin County's median reported result, 2008 to 2017.
The data
Hardin County, At a glance
Hardin County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Hardin County in
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 Hardin County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 22%4 pCi/L and above: 63%
Of 349 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 52 | 14.9% |
| 2 to 4 pCi/L | 78 | 22.3% |
| 4 pCi/L and above | 219 | 62.8% |
What these figures count
These are the 349 tests reported to CDC for Hardin 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).
Hardin County, Compared
Hardin County radon figures, compared
Calculated by Radon411More than half: 62.8% of the 349 radon tests reported to CDC for Hardin County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 53rd of 99 Iowa counties with 30 or more tests for the same period. That is 4.3 points above the 58.5% pooled from 99 Iowa counties.
The median result, 5.6 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 51.9 pCi/L. The rest split 14.9% under 2 pCi/L and 22.3% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 62.8% share point the same way here.
5 of its 7 bordering counties with figures ran higher, led by Franklin County at 73.5%; Butler County reported 59.9%. 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 Hardin County went from 309 tests (2005 to 2014) to 349 (2008 to 2017), the share going from 63.1% to 62.8%.
Nationally, every county with a figure for the same period pools to 35.7%; Hardin County sits 27.1 points above it. CDC also counts 52 tests taken after mitigation in Hardin County for the same period: tests in homes where a fix was already in.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Hardin County, Geology
The ground under Hardin County
PredictedUSGS's geologic map puts all of Hardin County's mapped land in one class: high radon potential. The map puts 67.9% of Hardin County in the area it calls Des Moines Lobe and 30.5% in Loess-Covered Drift Plains, with one smaller area beside them. USGS gives the first a radon index of 12 and the second 13, both in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Des Moines Lobe | Calcareous loamy till derived from shale, limestone, dolomite, sandstone. | High | 12 | 67.9% |
| Loess-Covered Drift Plains | Pre-Illinoian and Illinoian glacial deposits, and loess. | High | 13 | 30.5% |
| Iowan Surface | Pre-Illinoian glaical deposits and loess. | High | 12 | 1.5% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Hardin County beside the ground around it
On high-potential ground Hardin 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; Butler County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Hardin County, Local resources
Radon testing and mitigation in Hardin County
Listed radon businesses with an address in Hardin County:
- Iowa HHS Radon ProgramIowa HHS Radon Program, run by Iowa Department of Health and Human Services, licenses or certifies radon professionals, offers free or discounted test kits and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in Iowa.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
You can reach the Hotline by calling 1-800-383-5992 to order low-cost radon test kits and find answers to your radon questions.
- Compare kits
- Professionals in Iowa185 professionals are listed in Iowa.
Listed radon professionals by town: Iowa Falls, Steamboat Rock
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
Hardin County, Questions
Questions about radon in Hardin County
Are radon levels high in Hardin County?
Over the 2008 to 2017 laboratory totals, 62.8% of the radon tests reported to CDC for Hardin County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.6 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 52 reported a higher share; pooled, the state comes to 58.5%.
Which counties border Hardin County?
Hardin County borders 7 counties: Hamilton County, Grundy County, Story County, Marshall County, Franklin County, Butler County and Wright County.
Products
Hardin County, Products
Testing a home in Hardin County
In Hardin County, 62.8% of 349 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 Hardin 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 monitorMonitorSafetySiren
Pro4 plug-in radon detector with a display and alarm
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
First reading: Within 48 hours
Short-term kit
Radon Short Term Test Kit short-term charcoal radon test kit, lab fee included
- Lab fee included
Method: Charcoal
In home: 2 to 7 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Hardin County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Hardin County
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Hardin County, Bordering counties
Counties bordering Hardin County
Calculated by Radon411- Radon levels in Franklin CountyEPA zone 1
73.5%at or above 4 pCi/L
Median 6.2 pCi/L · 313 tests · 10.7 points above Hardin County
- Radon levels in Marshall CountyEPA zone 1
70.2%at or above 4 pCi/L
Median 8.2 pCi/L · 570 tests · 7.4 points above Hardin County
- Radon levels in Grundy CountyEPA zone 1
66.9%at or above 4 pCi/L
Median 6.9 pCi/L · 501 tests · 4.1 points above Hardin County
- Radon levels in Wright CountyEPA zone 1
66.8%at or above 4 pCi/L
Median 6.2 pCi/L · 292 tests · 4.0 points above Hardin County
- Radon levels in Hamilton CountyEPA zone 1
64.3%at or above 4 pCi/L
Median 5.5 pCi/L · 252 tests · 1.5 points above Hardin County
- Radon levels in Story CountyEPA zone 1
59.9%at or above 4 pCi/L
Median 5.0 pCi/L · 2,568 tests · 2.9 points below Hardin County
- Radon levels in Butler CountyEPA zone 1
59.9%at or above 4 pCi/L
Median 5.2 pCi/L · 377 tests · 2.9 points below Hardin County
Hardin County, Cities and towns
Cities and towns in Hardin County
About 16,455 people live in Hardin County by the Census Bureau's estimate for July 1, 2025, 376 fewer than in 2020 (−2.2%). That works out to 29 people per square mile of land. Its largest town, Iowa Falls, has 5,013 residents, 30.5% of the total. CDC's 349 reported tests for 2008 to 2017 work out to 21.2 per 1,000 residents (2025 estimate), close to Iowa's 29.4.
From Iowa Falls to Owasa, CDC publishes no figure by town: each reads Hardin County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Iowa Falls | 5,013 | −1.6% | 30.5% |
| Eldora | 2,593 | −2.4% | 15.8% |
| Ackleyextends beyond Hardin County | 1,530 | −3.8% | Counted whole |
| Hubbard | 835 | −2.7% | 5.1% |
| Alden | 735 | −3.4% | 4.5% |
| Radcliffe | 540 | −2.9% | 3.3% |
| Union | 382 | −3.0% | 2.3% |
| Steamboat Rock | 260 | −1.9% | 1.6% |
| New Providence | 229 | −2.6% | 1.4% |
| Whitten | 97 | −3.0% | 0.6% |
| Buckeye | 82 | −1.2% | 0.5% |
| Owasa | 30 | −3.2% | 0.2% |
12 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 Hardin County is counted whole, so it has no share.
Hardin County, Homes
Homes in Hardin County
Hardin County is a place of houses on their own lots: 84% of its 8,028 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1954 (1971 for Iowa), and 58% date from before 1960. 73% 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 | Hardin County | Iowa |
|---|---|---|
| Housing units | 8,028 | 1,427,175 |
| Detached houses | 84% | 72% |
| In buildings of 5 or more | 4% | 14% |
| Mobile homes | 2% | 3% |
| Built before 1960 | 58% | 39% |
| Built since 2000 | 5% | 21% |
| Middle year built | 1954 | 1971 |
| Owner-occupied | 73% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.