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 O'Brien County, Iowa
EPA puts O'Brien County in Zone 1, its highest radon zone, and high results are common there: 81.7% of the 652 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
81.7%
23.2 pts above IA
- O'Brien
- 81.7%
- Iowa
- 58.5%
652 tests, 2008 to 2017
Median result
8.9pCi/L
Action level reached
- O'Brien
- 8.9 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
652
37th of 99 by tests
- O'Brien
- 652
- 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
3 of 99
Top quarter
- O'Brien
- 81.7%
- Sioux
- 84.2%
By share, of 99 with 30+ tests
Read a result for O'Brien County
Starts at O'Brien County's median, 8.9 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 8.9 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. O'Brien County's median reported result, 2008 to 2017.
The data
O'Brien County, At a glance
O'Brien County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of O'Brien 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 O'Brien County, 2008 to 2017, laboratory
Under 2 pCi/L: 8%2 to 4 pCi/L: 10%4 pCi/L and above: 82%
Of 652 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 53 | 8.1% |
| 2 to 4 pCi/L | 66 | 10.1% |
| 4 pCi/L and above | 533 | 81.7% |
What these figures count
These are the 652 tests reported to CDC for O'Brien 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).
O'Brien County, Compared
O'Brien County radon figures, compared
Calculated by Radon411More than half: 81.7% of the 652 radon tests reported to CDC for O'Brien County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 3rd of 99 Iowa counties with 30 or more tests for the same period. That is 23.2 points above the 58.5% pooled from 99 Iowa counties.
The median result, 8.9 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 73.7 pCi/L. The rest split 8.1% under 2 pCi/L and 10.1% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 81.7% share point the same way here.
2 of its 8 bordering counties with figures ran higher, led by Sioux County at 84.2%; Osceola County reported 67.2%. 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 O'Brien County went from 468 tests (2005 to 2014) to 652 (2008 to 2017), the share going from 82.9% to 81.7%.
Nationally, every county with a figure for the same period pools to 35.7%; O'Brien County sits 46.0 points above it. CDC also counts 53 tests taken after mitigation in O'Brien 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.
O'Brien County, Geology
The ground under O'Brien County
PredictedUSGS's geologic map puts all of O'Brien 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).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Loess-Covered Drift Plains | Pre-Illinoian and Illinoian glacial deposits, and loess. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
O'Brien County beside the ground around it
On high-potential ground O'Brien County is close to Iowa as a whole: 100% of its land against 98.8%. Of the 8 counties that border it, none has as large a share of high-potential ground; Cherokee County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
O'Brien County, Local resources
Radon testing and mitigation in O'Brien 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
O'Brien County, Questions
Questions about radon in O'Brien County
Are radon levels high in O'Brien County?
Over the 2008 to 2017 laboratory totals, 81.7% of the radon tests reported to CDC for O'Brien County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 8.9 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 58.5%.
Which counties border O'Brien County?
O'Brien County borders 8 counties: Osceola County, Clay County, Sioux County, Cherokee County, Dickinson County, Lyon County, Buena Vista County and Plymouth County.
Products
O'Brien County, Products
Testing a home in O'Brien County
In O'Brien County, 81.7% of 652 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 O'Brien 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
MonitorAEGTEST
HOUND-3786 rechargeable radon monitor with a 3.5-inch color screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Ion chamber
First reading: Within 10 minutes
Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
O'Brien County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like O'Brien County
Explore
O'Brien County, Bordering counties
Counties bordering O'Brien County
Calculated by Radon411- Radon levels in Sioux CountyEPA zone 1
84.2%at or above 4 pCi/L
Median 10.7 pCi/L · 1,982 tests · 2.5 points above O'Brien County
- Radon levels in Plymouth CountyEPA zone 1
82.3%at or above 4 pCi/L
Median 8.6 pCi/L · 1,405 tests · 0.6 points above O'Brien County
- Radon levels in Clay CountyEPA zone 1
79.4%at or above 4 pCi/L
Median 9.6 pCi/L · 744 tests · 2.3 points below O'Brien County
- Radon levels in Lyon CountyEPA zone 1
77.6%at or above 4 pCi/L
Median 8.3 pCi/L · 237 tests · 4.1 points below O'Brien County
- Radon levels in Cherokee CountyEPA zone 1
74.5%at or above 4 pCi/L
Median 7.6 pCi/L · 795 tests · 7.2 points below O'Brien County
- Radon levels in Buena Vista CountyEPA zone 1
72.1%at or above 4 pCi/L
Median 6.9 pCi/L · 688 tests · 9.6 points below O'Brien County
- Radon levels in Dickinson CountyEPA zone 1
70.3%at or above 4 pCi/L
Median 7.0 pCi/L · 831 tests · 11.4 points below O'Brien County
- Radon levels in Osceola CountyEPA zone 1
67.2%at or above 4 pCi/L
Median 6.8 pCi/L · 122 tests · 14.5 points below O'Brien County
O'Brien County, Cities and towns
Cities and towns in O'Brien County
O'Brien County's population has barely moved since 2020: 14,220 residents on July 1, 2025 against 14,156 then, by the Census Bureau's estimates. That works out to 25 people per square mile of land. Sheldon, the largest place on its list (5,575 residents in all), extends beyond O'Brien County, so no share of the total is worked out for it. Testing is reported here more often than across the state: CDC's 652 reported tests for 2008 to 2017 come to 45.9 for every 1,000 residents (2025 estimate), against 29.4 for Iowa.
From Sheldon to Archer, CDC publishes no figure by town: each reads O'Brien County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Sheldonextends beyond O'Brien County | 5,575 | +1.4% | Counted whole |
| Hartley | 1,579 | −1.4% | 11.1% |
| Sanborn | 1,463 | +5.0% | 10.3% |
| Paullina | 970 | −0.6% | 6.8% |
| Primghar | 894 | −1.1% | 6.3% |
| Sutherland | 626 | −0.5% | 4.4% |
| Calumet | 144 | −2.0% | 1.0% |
| Archer | 116 | −0.9% | 0.8% |
8 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 O'Brien County is counted whole, so it has no share.
O'Brien County, Homes
Homes in O'Brien County
O'Brien County is a place of houses on their own lots: 84% of its 6,544 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1959 (1971 for Iowa), and 52% date from before 1960. Owners live in 77% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.
| Homes | O'Brien County | Iowa |
|---|---|---|
| Housing units | 6,544 | 1,427,175 |
| Detached houses | 84% | 72% |
| In buildings of 5 or more | 9% | 14% |
| Mobile homes | 2% | 3% |
| Built before 1960 | 52% | 39% |
| Built since 2000 | 11% | 21% |
| Middle year built | 1959 | 1971 |
| Owner-occupied | 77% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.