Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Carroll County, Iowa
EPA puts Carroll County in Zone 1, its highest radon zone, and high results are common there: 77.6% of the 594 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
77.6%
19.1 pts above IA
- Carroll
- 77.6%
- Iowa
- 58.5%
594 tests, 2008 to 2017
Median result
7.8pCi/L
Action level reached
- Carroll
- 7.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
594
40th of 99 by tests
- Carroll
- 594
- 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
8 of 99
Top quarter
- Carroll
- 77.6%
- Sioux
- 84.2%
By share, of 99 with 30+ tests
Read a result for Carroll County
Starts at Carroll County's median, 7.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 7.8 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. Carroll County's median reported result, 2008 to 2017.
The data
Carroll County, At a glance
Carroll County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Carroll 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 Carroll County, 2008 to 2017, laboratory
Under 2 pCi/L: 9%2 to 4 pCi/L: 13%4 pCi/L and above: 78%
Of 594 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 56 | 9.4% |
| 2 to 4 pCi/L | 77 | 13.0% |
| 4 pCi/L and above | 461 | 77.6% |
What these figures count
These are the 594 tests reported to CDC for Carroll 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).
Carroll County, Compared
Carroll County radon figures, compared
Calculated by Radon411More than half: 77.6% of the 594 radon tests reported to CDC for Carroll County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 8th of 99 Iowa counties with 30 or more tests for the same period. That is 19.1 points above the 58.5% pooled from 99 Iowa counties.
The median result, 7.8 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 149.5 pCi/L. The rest split 9.4% under 2 pCi/L and 13.0% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 77.6% share point the same way here.
2 of its 7 bordering counties with figures ran higher, led by Shelby County at 78.4%; Calhoun County reported 69.8%. 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 Carroll County went from 625 tests (2005 to 2014) to 594 (2008 to 2017), the share going from 80.2% to 77.6%.
Nationally, every county with a figure for the same period pools to 35.7%; Carroll County sits 41.9 points above it. CDC also counts 43 tests taken after mitigation in Carroll 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.
Carroll County, Geology
The ground under Carroll County
PredictedUSGS's geologic map puts all of Carroll County's mapped land in one class: high radon potential. The map puts 58.5% of Carroll County in the area it calls Des Moines Lobe and 41.5% in Loess-Covered Drift Plains. 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 | 58.5% |
| Loess-Covered Drift Plains | Pre-Illinoian and Illinoian glacial deposits, and loess. | High | 13 | 41.5% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Carroll County beside the ground around it
On high-potential ground Carroll 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; Audubon County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Carroll County, Local resources
Radon testing and mitigation in Carroll 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.
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
Carroll County, Questions
Questions about radon in Carroll County
Are radon levels high in Carroll County?
Over the 2008 to 2017 laboratory totals, 77.6% of the radon tests reported to CDC for Carroll County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 7.8 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 7 reported a higher share; pooled, the state comes to 58.5%.
Which counties border Carroll County?
Carroll County borders 7 counties: Audubon County, Greene County, Sac County, Calhoun County, Crawford County, Guthrie County and Shelby County.
Products
Carroll County, Products
Testing a home in Carroll County
In Carroll County, 77.6% of 594 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 Carroll 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
Monitor
EcoBlu plug-in digital radon monitor with a display
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
Method: Ion chamber
First reading: Within 10 minutes
Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Carroll County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Carroll County
Explore
Carroll County, Bordering counties
Counties bordering Carroll County
Calculated by Radon411- Radon levels in Shelby CountyEPA zone 1
78.4%at or above 4 pCi/L
Median 9.0 pCi/L · 857 tests · 0.8 points above Carroll County
- Radon levels in Audubon CountyEPA zone 1
78.3%at or above 4 pCi/L
Median 9.5 pCi/L · 189 tests · 0.7 points above Carroll County
- Radon levels in Sac CountyEPA zone 1
76.6%at or above 4 pCi/L
Median 7.0 pCi/L · 491 tests · 1.0 points below Carroll County
- Radon levels in Crawford CountyEPA zone 1
74.8%at or above 4 pCi/L
Median 7.0 pCi/L · 373 tests · 2.8 points below Carroll County
- Radon levels in Greene CountyEPA zone 1
71.3%at or above 4 pCi/L
Median 6.2 pCi/L · 143 tests · 6.3 points below Carroll County
- Radon levels in Guthrie CountyEPA zone 1
70.8%at or above 4 pCi/L
Median 6.9 pCi/L · 257 tests · 6.8 points below Carroll County
- Radon levels in Calhoun CountyEPA zone 1
69.8%at or above 4 pCi/L
Median 6.1 pCi/L · 507 tests · 7.8 points below Carroll County
Carroll County, Cities and towns
Cities and towns in Carroll County
About 20,303 people live in Carroll County by the Census Bureau's estimate for July 1, 2025, 422 fewer than in 2020 (−2.0%). That works out to 36 people per square mile of land. Its largest town, Carroll, has 10,085 residents, 49.7% of the total. CDC's 594 reported tests for 2008 to 2017 work out to 29.3 per 1,000 residents (2025 estimate), close to Iowa's 29.4.
From Carroll to Willey, CDC publishes no figure by town: each reads Carroll County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Carroll | 10,085 | −2.2% | 49.7% |
| Manning | 1,375 | −5.2% | 6.8% |
| Coon Rapidsextends beyond Carroll County | 1,251 | −3.9% | Counted whole |
| Glidden | 1,133 | −1.4% | 5.6% |
| Arcadia | 586 | +11.0% | 2.9% |
| Breda | 488 | −2.6% | 2.4% |
| Templeton | 339 | −2.6% | 1.7% |
| Halbur | 266 | −2.2% | 1.3% |
| Dedham | 219 | −1.4% | 1.1% |
| Lidderdale | 159 | −4.8% | 0.8% |
| Lanesboro | 112 | −5.1% | 0.6% |
| Ralstonextends beyond Carroll County | 75 | −3.8% | Counted whole |
- Willey
13 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Carroll County is counted whole, so it has no share.
Carroll County, Homes
Homes in Carroll County
Carroll County is a place of houses on their own lots: 81% of its 9,508 homes are detached single-family houses, against 72% across Iowa. Half of its homes were built before 1964, close to Iowa's 1971: 46% date from before 1960 and 13% from 2000 or later. Owners live in 75% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.
| Homes | Carroll County | Iowa |
|---|---|---|
| Housing units | 9,508 | 1,427,175 |
| Detached houses | 81% | 72% |
| In buildings of 5 or more | 10% | 14% |
| Mobile homes | 1% | 3% |
| Built before 1960 | 46% | 39% |
| Built since 2000 | 13% | 21% |
| Middle year built | 1964 | 1971 |
| Owner-occupied | 75% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.