Short-term kitKidde
442020 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 3 days
Locations and reports
Radon Levels in Dewey County, South Dakota
EPA puts Dewey County in Zone 2, its middle radon zone, and only 1 radon test from it is 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
Nearest county
66.7%
Hughes County, 68 miles
- Hughes
- 66.7%
- SD
- 58.8%
Share at 4+ pCi/L, 30 tests, 2006 to 2015
Ground above low
100.0%
1.0 pts above SD
- Dewey
- 100.0%
- SD
- 99.0%
Share of land USGS rates moderate or high potential
Tests reported
1
Too few for a share
- Dewey
- 1
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Read a result for Dewey 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
Dewey County, At a glance
Dewey County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Dewey County is a
USGS geologic potential: Moderate across 54% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Dewey County, 2008 to 2017, laboratory
CDC holds 1 reported test for Dewey County over the 2008 to 2017 laboratory totals, a result of 0.6 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Dewey County beside the counties around it is how this page reads it.
What these figures count
Only 1 test was reported to CDC for Dewey 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).
Dewey County, Compared
Dewey County radon figures, compared
Calculated by Radon411CDC's largest figure for Dewey County rests on 1 test over the 2008 to 2017 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 100.0 points and no rank or comparison is drawn from it. Results reached as high as 0.6 pCi/L, with a middle value of 0.6 pCi/L.
The nearest counties with a figure are Hughes County (68 miles away) at 66.7%, Edmunds County (83 miles away) at 61.8% and Meade County (99 miles away) at 54.5%. Pooled across 63 South Dakota counties, 58.8% of reported tests reached that level; across every county in the country with a figure, 36.3%.
Statewide for the same period, Bon Homme County reported the highest share (79.5%) and Davison County the lowest (47.9%). EPA's 1993 map puts Dewey County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 54% of the county's land moderate radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Dewey County, Geology
The ground under Dewey County
PredictedUSGS's geologic map splits Dewey County: 54.2% of its land is moderate radon potential and 45.8% high. The map puts 54.2% of Dewey County in the area it calls Pierre Hills and 45.8% in Missouri Coteau/James River Lowland/Coteau des Prairies. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 14, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Pierre Hills | Pierre Shale and Fox Hills sandstone. | Moderate | 10 | 54.2% |
| Missouri Coteau/James River Lowland/Coteau des Prairies | Glacial drift derived largely from Cretaceous marine shale. | High | 14 | 45.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Dewey County beside the ground around it
South Dakota as a whole has more high-potential ground than Dewey County: 56.7% of its land, against 45.8% here. Of the 7 counties that border it, 5 have more high-potential ground, Potter County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Dewey County, Local resources
Radon testing and mitigation in Dewey County
- South Dakota's radon programDepartment of Agriculture and Natural ResourcesSouth Dakota's radon program offers free or discounted test kits, and answers questions about testing and mitigation in South Dakota.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The Department of Agriculture and Natural Resources (DANR) will provide 500 free Radon test kits to South Dakota Residents.
- Compare kits
- Professionals in South Dakota5 professionals are listed in South Dakota.
What South Dakota's program says
- Phone
- 1-800-438-3367
What it means
Dewey County, Questions
Questions about radon in Dewey County
Are radon levels high in Dewey County?
Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Dewey County, South Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.6 pCi/L. Of the 8 nearest counties with a figure, within 154 miles, the share of tests at or above 4 pCi/L runs from 51.8% to 66.7%.
Which counties border Dewey County?
Dewey County borders 7 counties: Ziebach County, Stanley County, Sully County, Potter County, Corson County, Walworth County and Haakon County.
Products
Dewey County, Products
Testing a home in Dewey County
No CDC figure names Dewey County; the nearest county with one, Hughes County (68 miles away), reported 66.7% of its tests at or above 4 pCi/L over the 2006 to 2015 laboratory totals, the only reading nearby until a test of this home. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Dewey County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
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
MonitorSafetySiren
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
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Dewey County, Bordering counties
Counties bordering Dewey County
Calculated by Radon411- Radon levels in Ziebach CountyEPA zone 2
100.0%at or above 4 pCi/L
Median 11.6 pCi/L · 3 tests
- Radon levels in Stanley CountyEPA zone 1
100.0%at or above 4 pCi/L
Median 5.2 pCi/L · 2 tests
- Radon levels in Sully CountyEPA zone 1
100.0%at or above 4 pCi/L
Median 4.1 pCi/L · 1 test
- Radon levels in Walworth CountyEPA zone 1
81.3%at or above 4 pCi/L
Median 6.1 pCi/L · 16 tests
- Radon levels in Corson CountyEPA zone 1
50.0%at or above 4 pCi/L
Median 8.0 pCi/L · 2 tests
- Radon levels in Haakon CountyEPA zone 2
50.0%at or above 4 pCi/L
Median 6.3 pCi/L · 2 tests
- Radon levels in Potter CountyEPA zone 1
0.0%at or above 4 pCi/L
Median 1.2 pCi/L · 1 test
Dewey County, Cities and towns
Cities and towns in Dewey County
The Census Bureau estimates 5,419 residents in Dewey County for July 1, 2025, 196 more than in 2020 (+3.8%). Spread over its land, that is 2.4 people to the square mile. Eagle Butte, the largest place on its list (1,269 residents in all), extends beyond Dewey County, so no share of the total is worked out for it. Reported testing is thin here: 1 test over 2008 to 2017, or 0.2 for every 1,000 residents (2025 estimate), where South Dakota as a whole comes to 6.7.
From Eagle Butte to Isabel, CDC publishes no figure by town: each reads Dewey County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Eagle Butteextends beyond Dewey County | 1,269 | +1.8% | Counted whole |
| Timber Lake | 548 | +7.0% | 10.1% |
| Isabel | 162 | +12.5% | 3.0% |
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). A place that extends beyond Dewey County is counted whole, so it has no share.
Dewey County, Homes
Homes in Dewey County
Of Dewey County's 1,927 homes, 72% are detached houses, against 67% across South Dakota; 18% are mobile homes. Half of its homes were built before 1977, close to South Dakota's 1979: 21% date from before 1960 and 13% from 2000 or later. 61% of occupied homes are lived in by their owner (South Dakota: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Dewey County | South Dakota |
|---|---|---|
| Housing units | 1,927 | 402,364 |
| Detached houses | 72% | 67% |
| In buildings of 5 or more | 5% | 16% |
| Mobile homes | 18% | 8% |
| Built before 1960 | 21% | 29% |
| Built since 2000 | 13% | 28% |
| Middle year built | 1977 | 1979 |
| Owner-occupied | 61% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.