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 Sioux County, North Dakota
EPA puts Sioux County in Zone 1, its highest radon zone, and only 2 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
53.4%
Morton County
- Morton
- 53.4%
1 of 6 neighbours have 30+ tests, 2008 to 2017
Nearest county
53.4%
Morton County, 43 miles
- Morton
- 53.4%
- ND
- 59.3%
Share at 4+ pCi/L, 268 tests, 2008 to 2017
Ground above low
100.0%
Level with ND
- Sioux
- 100.0%
- ND
- 100.0%
Share of land USGS rates moderate or high potential
Tests reported
2
Too few for a share
- Sioux
- 2
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Read a result for Sioux County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 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.
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 79% 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
CDC holds 2 reported tests for Sioux County over the 2008 to 2017 laboratory totals, with a median of 9.3 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Sioux County beside the counties around it is how this page reads it.
What these figures count
Only 2 tests were reported to CDC for Sioux County over 2008 to 2017 (laboratory totals), and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor 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 Radon411CDC's largest figure for Sioux County rests on 2 tests over the 2008 to 2017 laboratory totals, 2 of them at or above 4 pCi/L, so each test moves its share by 50.0 points and no rank or comparison is drawn from it. Results reached as high as 11.7 pCi/L, with a middle value of 9.3 pCi/L.
Morton County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 53.4% of its tests at or above 4 pCi/L. Farther out, Burleigh County (66 miles away) at 51.1%, McIntosh County (77 miles away) at 71.9% and Mercer County (91 miles away) at 63.5% have figures too. Pooled across 53 North Dakota counties, 59.3% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Pembina County reported the highest share (82.5%) and Williams County the lowest (33.8%). EPA's 1993 map puts Sioux County in Zone 1, the map's highest label: a predicted county average above 4 pCi/L. USGS geology rates 79% of the county's land high radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Sioux County, Geology
The ground under Sioux County
PredictedMost of the ground under Sioux County is one class on USGS's geologic map: 78.6% of its land is high radon potential, with 21.4% moderate. The map puts 66.1% of Sioux County in the area it calls Great Plains (Glaciated) and 21.4% in Pierre Hills, with one smaller area beside them. USGS gives the first a radon index of 13, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Great Plains (Glaciated) | Glacial deposits derived from Cretaceous shales containing higher than average amounts of uranium. | High | 13 | 66.1% |
| Pierre Hills | Pierre Shale and Fox Hills sandstone. | Moderate | 10 | 21.4% |
| Great Plains (Unglaciated) | Tertiary and Upper Cretaceous sandstones, shales, and locally, coal-bearing units. | High | 13 | 12.5% |
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
North Dakota as a whole has more high-potential ground than Sioux County: 98.9% of its land, against 78.6% here. Of the 6 counties that border it, 4 have more high-potential ground, Adams County the most 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
- North Dakota's radon programNorth Dakota Department of Environmental QualityNorth Dakota's radon program offers free or discounted test kits, and answers questions about testing and mitigation in North Dakota.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Notice: The DEQ is out of free radon test kits.
- Compare kits
- Professionals in North Dakota47 professionals are listed in North Dakota.
What North Dakota's program says
- Phone
- 701-328-5166
- jOtto@nd.gov
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, 100.0% of the radon tests reported to CDC for Sioux County, North Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 9.3 pCi/L. Morton County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 53.4% of its tests at or above 4 pCi/L.
Which counties border Sioux County?
Sioux County borders 6 counties: Emmons County, ND, Corson County, SD, Grant County, ND, Morton County, ND, Adams County, ND and Perkins County, SD.
Products
Sioux County, Products
Testing a home in Sioux County
No CDC figure names Sioux County; the nearest county with one, Morton County (43 miles away), reported 53.4% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. 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
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
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 Emmons County, NDEPA zone 1
86.2%at or above 4 pCi/L
Median 7.1 pCi/L · 29 tests
- Radon levels in Adams County, NDEPA zone 1
80.0%at or above 4 pCi/L
Median 12.7 pCi/L · 10 tests
- Radon levels in Perkins County, SDEPA zone 1
76.9%at or above 4 pCi/L
Median 8.1 pCi/L · 13 tests
- Radon levels in Grant County, NDEPA zone 1
73.9%at or above 4 pCi/L
Median 7.4 pCi/L · 23 tests
- Radon levels in Morton County, NDEPA zone 1
53.4%at or above 4 pCi/L
Median 4.2 pCi/L · 268 tests
- Radon levels in Corson County, SDEPA zone 1
No CDC figure for 2008 to 2017; its page reads it against its own neighbours.
Sioux County, Cities and towns
Cities and towns in Sioux County
Sioux County has been losing residents: from 3,876 in 2020 to 3,667 on July 1, 2025, a fall of 5.4% by the Census Bureau's estimates. Spread over its land, that is 3.4 people to the square mile. No town dominates: Fort Yates, the largest, has 167 residents, 4.6% of the total. Together its 3 incorporated places hold 9.6% of those residents; the other 90.4% live outside any of them. Reported testing is thin here: 2 tests over 2008 to 2017, or 0.5 for every 1,000 residents (2025 estimate), where North Dakota as a whole comes to 8.3.
From Fort Yates to Solen, CDC publishes no figure by town: each reads Sioux County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Fort Yates | 167 | −5.6% | 4.6% |
| Selfridge | 119 | −5.6% | 3.2% |
| Solen | 66 | −5.7% | 1.8% |
3 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).
Sioux County, Homes
Homes in Sioux County
Sioux County is a place of houses on their own lots: 79% of its 1,276 homes are detached single-family houses, against 57% across North Dakota. Half of its homes were built before 1982, close to North Dakota's 1981: 15% date from before 1960 and 22% from 2000 or later. Most occupied homes here are rented: owners live in 46% (North Dakota: 63%). A tenant can run a test; a fix is the landlord's to make.
| Homes | Sioux County | North Dakota |
|---|---|---|
| Housing units | 1,276 | 374,866 |
| Detached houses | 79% | 57% |
| In buildings of 5 or more | 2% | 25% |
| Mobile homes | 12% | 7% |
| Built before 1960 | 15% | 24% |
| Built since 2000 | 22% | 31% |
| Middle year built | 1982 | 1981 |
| Owner-occupied | 46% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.