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 Sioux County, Iowa
EPA puts Sioux County in Zone 1, its highest radon zone, and high results are common there: 84.2% of the 1,982 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
84.2%
25.7 pts above IA
- Sioux
- 84.2%
- Iowa
- 58.5%
1,982 tests, 2008 to 2017
Median result
10.7pCi/L
Action level reached
- Sioux
- 10.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
1,982
10th of 99 by tests
- Sioux
- 1,982
- 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
1 of 99
Top quarter
- Sioux
- 84.2%
- Sioux
- 84.2%
By share, of 99 with 30+ tests
Read a result for Sioux County
Starts at Sioux County's median, 10.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 10.7 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. Sioux County's median reported result, 2008 to 2017.
The data
Sioux County, At a glance
Sioux County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Sioux 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 Sioux County, 2008 to 2017, laboratory
Under 2 pCi/L: 9%2 to 4 pCi/L: 7%4 pCi/L and above: 84%
Of 1,982 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 181 | 9.1% |
| 2 to 4 pCi/L | 132 | 6.7% |
| 4 pCi/L and above | 1,669 | 84.2% |
What these figures count
These are the 1,982 tests reported to CDC for Sioux 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).
Sioux County, Compared
Sioux County radon figures, compared
Calculated by Radon411More than half: 84.2% of the 1,982 radon tests reported to CDC for Sioux County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 1st of 99 Iowa counties with 30 or more tests for the same period. That is 25.7 points above the 58.5% pooled from 99 Iowa counties.
The median result, 10.7 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 106.2 pCi/L. The rest split 9.1% under 2 pCi/L and 6.7% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 84.2% share point the same way here.
No bordering county with a figure for the same period reported a higher share; the closest is Plymouth County at 82.3%, the lowest Union County, SD at 51.1%. Statewide for the same period, Plymouth County reported the highest share (82.3%) and Decatur County the lowest (25.9%).
CDC's ten-year totals for Sioux County went from 1,572 tests (2005 to 2014) to 1,982 (2008 to 2017), the share going from 86.8% to 84.2%.
Nationally, every county with a figure for the same period pools to 35.7%; Sioux County sits 48.5 points above it. CDC also counts 235 tests taken after mitigation in Sioux 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.
Sioux County, Geology
The ground under Sioux County
PredictedUSGS's geologic map puts all of Sioux 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.
Sioux County beside the ground around it
On high-potential ground Sioux 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; Cherokee County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Sioux County, Local resources
Radon testing and mitigation in Sioux County
Listed radon businesses with an address in Sioux 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: Sioux Center, Rock Valley
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
Sioux County, Questions
Questions about radon in Sioux County
Are radon levels high in Sioux County?
Over the 2008 to 2017 laboratory totals, 84.2% of the radon tests reported to CDC for Sioux County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 10.7 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 58.5%.
Which counties border Sioux County?
Sioux County borders 7 counties: Lyon County, IA, Plymouth County, IA, O'Brien County, IA, Lincoln County, SD, Osceola County, IA, Union County, SD and Cherokee County, IA.
Products
Sioux County, Products
Testing a home in Sioux County
In Sioux County, 84.2% of 1,982 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 Sioux 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
RM-65 rechargeable radon detector with a color screen and alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
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
Sioux County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Sioux County
Explore
Sioux County, Bordering counties
Counties bordering Sioux County
Calculated by Radon411- Radon levels in Plymouth County, IAEPA zone 1
82.3%at or above 4 pCi/L
Median 8.6 pCi/L · 1,405 tests · 1.9 points below Sioux County
- Radon levels in O'Brien County, IAEPA zone 1
81.7%at or above 4 pCi/L
Median 8.9 pCi/L · 652 tests · 2.5 points below Sioux County
- Radon levels in Lyon County, IAEPA zone 1
77.6%at or above 4 pCi/L
Median 8.3 pCi/L · 237 tests · 6.6 points below Sioux County
- Radon levels in Cherokee County, IAEPA zone 1
74.5%at or above 4 pCi/L
Median 7.6 pCi/L · 795 tests · 9.7 points below Sioux County
- Radon levels in Osceola County, IAEPA zone 1
67.2%at or above 4 pCi/L
Median 6.8 pCi/L · 122 tests · 17.0 points below Sioux County
- Radon levels in Lincoln County, SDEPA zone 1
56.5%at or above 4 pCi/L
Median 4.7 pCi/L · 795 tests · 27.7 points below Sioux County
- Radon levels in Union County, SDEPA zone 1
51.1%at or above 4 pCi/L
Median 4.1 pCi/L · 348 tests · 33.1 points below Sioux County
Sioux County, Cities and towns
Cities and towns in Sioux County
The Census Bureau estimates 36,774 residents in Sioux County for July 1, 2025, 886 more than in 2020 (+2.5%). That works out to 48 people per square mile of land. Its largest town, Sioux Center, has 8,864 residents, 24.1% of the total. Testing is reported here more often than across the state: CDC's 1,982 reported tests for 2008 to 2017 come to 53.9 for every 1,000 residents (2025 estimate), against 29.4 for Iowa.
From Sioux Center to Chatsworth, CDC publishes no figure by town: each reads Sioux County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Sioux Center | 8,864 | +7.6% | 24.1% |
| Orange City | 6,468 | +3.1% | 17.6% |
| Sheldonextends beyond Sioux County | 5,575 | +1.4% | Counted whole |
| Rock Valley | 4,188 | +2.9% | 11.4% |
| Hawarden | 2,665 | −1.3% | 7.2% |
| Hull | 2,457 | +3.8% | 6.7% |
| Alton | 1,254 | +1.3% | 3.4% |
| Hospers | 691 | −4.0% | 1.9% |
| Boyden | 688 | −2.1% | 1.9% |
| Ireton | 567 | −2.4% | 1.5% |
| Granville | 299 | −3.9% | 0.8% |
| Maurice | 267 | Level | 0.7% |
- Matlock
- Chatsworth
14 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 Sioux County is counted whole, so it has no share.
Sioux County, Homes
Homes in Sioux County
Sioux County is a place of houses on their own lots: 80% of its 13,175 homes are detached single-family houses, against 72% across Iowa. Half of its homes were built before 1972, close to Iowa's 1971: 35% date from before 1960 and 19% from 2000 or later. Owners live in 78% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.
| Homes | Sioux County | Iowa |
|---|---|---|
| Housing units | 13,175 | 1,427,175 |
| Detached houses | 80% | 72% |
| In buildings of 5 or more | 7% | 14% |
| Mobile homes | 2% | 3% |
| Built before 1960 | 35% | 39% |
| Built since 2000 | 19% | 21% |
| Middle year built | 1972 | 1971 |
| Owner-occupied | 78% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.