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
Locations and reports
Radon Levels in Pennington County, South Dakota
EPA puts Pennington County in Zone 2, its middle radon zone, and high results are common there: 53.6% of the 1,029 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
53.6%
4.9 pts below SD
- Pennington
- 53.6%
- SD
- 58.5%
1,029 tests, 2008 to 2017
Median result
4.3pCi/L
Action level reached
- Pennington
- 4.3 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
1,029
2nd of 23 by tests
- Pennington
- 1,029
- Minnehaha
- 1,920
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in SD
18 of 23
Lowest quarter
- Pennington
- 53.6%
- Lake
- 76.0%
By share, of 23 with 30+ tests
Read a result for Pennington County
Starts at Pennington County's median, 4.3 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.3 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. Pennington County's median reported result, 2008 to 2017.
The data
Pennington County, At a glance
Pennington County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Pennington County is a
USGS geologic potential: Moderate across 96% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Pennington County, 2008 to 2017, laboratory
Under 2 pCi/L: 28%2 to 4 pCi/L: 18%4 pCi/L and above: 54%
Of 1,029 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 290 | 28.2% |
| 2 to 4 pCi/L | 187 | 18.2% |
| 4 pCi/L and above | 552 | 53.6% |
What these figures count
These are the 1,029 tests reported to CDC for Pennington 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).
Pennington County, Compared
Pennington County radon figures, compared
Calculated by Radon411More than half: 53.6% of the 1,029 radon tests reported to CDC for Pennington County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 18th of 23 South Dakota counties with 30 or more tests for the same period. That is 4.9 points below the 58.5% pooled from 62 South Dakota counties.
The median result, 4.3 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 823.0 pCi/L. The rest split 28.2% under 2 pCi/L and 18.2% from 2 to 4 (South Dakota: 23.6% and 17.9%). The reported tests do not follow EPA's Zone 2 label for Pennington County (predicted average between 2 and 4 pCi/L): 53.6% of them reached 4 pCi/L, fewer than that label suggests.
3 of its 4 bordering counties with figures ran higher, led by Custer County at 65.7%; Meade County reported 51.8%. Statewide for the same period, Lake County reported the highest share (76.0%) and Davison County the lowest (48.8%).
CDC's ten-year totals for Pennington County went from 664 tests (2005 to 2014) to 1,029 (2008 to 2017), the share going from 54.4% to 53.6%.
Nationally, every county with a figure for the same period pools to 35.7%; Pennington County sits 17.9 points above it. CDC also counts 11 tests taken after mitigation in Pennington 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.
Pennington County, Geology
The ground under Pennington County
PredictedMost of the ground under Pennington County is one class on USGS's geologic map: 96.0% of its land is moderate radon potential, with 4.0% high. The map puts 48.0% of Pennington County in the area it calls Pierre Hills and 28.8% in Black Hills, with 2 smaller areas beside them. USGS gives the first a radon index of 10 and the second 11, both in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Pierre Hills | Pierre Shale and Fox Hills sandstone. | Moderate | 10 | 48.0% |
| Black Hills | Late Paleozoic sedimentary or Precambrian intrusive igneous rocks. | Moderate | 11 | 28.8% |
| Southern Plateaus | Late Tertiary continental sandstone. | Moderate | 11 | 19.2% |
| Black Hills | Sandstones and shales of Cretaceous age that surround the Black Hills. | High | 14 | 4.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Pennington County beside the ground around it
South Dakota as a whole has more high-potential ground than Pennington County: 56.7% of its land, against 4.0% here. Of the 7 counties that border it, 4 have more high-potential ground, Weston County, WY the most at 45.1%.
The map rates the ground, not the air in any home.
Local help
Pennington County, Local resources
Radon testing and mitigation in Pennington 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
Pennington County, Questions
Questions about radon in Pennington County
Are radon levels high in Pennington County?
Over the 2008 to 2017 laboratory totals, 53.6% of the radon tests reported to CDC for Pennington County, South Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.3 pCi/L. Of 23 South Dakota counties with 30 or more tests for the same period, 17 reported a higher share; pooled, the state comes to 58.5%.
Which counties border Pennington County?
Pennington County borders 7 counties: Custer County, SD, Meade County, SD, Lawrence County, SD, Oglala Lakota County, SD, Jackson County, SD, Haakon County, SD and Weston County, WY.
Products
Pennington County, Products
Testing a home in Pennington County
In Pennington County, 53.6% of 1,029 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 58.5% pooled across South Dakota. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Pennington 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
Monitor
RadonPro Wi-Fi radon monitor with a built-in Geiger counter
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Pennington County, Bordering counties
Counties bordering Pennington County
Calculated by Radon411- Radon levels in Haakon County, SDEPA zone 2
80.0%at or above 4 pCi/L
Median 8.0 pCi/L · 5 tests · 26.4 points above Pennington County
- Radon levels in Custer County, SDEPA zone 2
65.7%at or above 4 pCi/L
Median 6.2 pCi/L · 108 tests · 12.1 points above Pennington County
- Radon levels in Weston County, WYEPA zone 2
65.6%at or above 4 pCi/L
Median 6.3 pCi/L · 32 tests · 12.0 points above Pennington County
- Radon levels in Lawrence County, SDEPA zone 2
56.9%at or above 4 pCi/L
Median 5.3 pCi/L · 160 tests · 3.3 points above Pennington County
- Radon levels in Meade County, SDEPA zone 2
51.8%at or above 4 pCi/L
Median 4.1 pCi/L · 197 tests · 1.8 points below Pennington County
- Radon levels in Jackson County, SDEPA zone 2
0.0%at or above 4 pCi/L
Median 1.1 pCi/L · 1 test · 53.6 points below Pennington County
- Radon levels in Oglala Lakota County, SDEPA zone 2
No CDC figure for 2008 to 2017; its page reads it against its own neighbours.
Pennington County, Cities and towns
Cities and towns in Pennington County
Pennington County is growing: the Census Bureau puts it at 116,792 residents on July 1, 2025, up 6.6% from 109,570 in 2020. That works out to 42 people per square mile of land. Rapid City alone is home to 80,589 of them, 69.0% of the total. CDC's 1,029 reported tests for 2008 to 2017 work out to 8.8 per 1,000 residents (2025 estimate), close to South Dakota's 6.7.
From Rapid City to Wasta, CDC publishes no figure by town: each reads Pennington County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Rapid City | 80,589 | +7.5% | 69.0% |
| Box Elderextends beyond Pennington County | 13,936 | +16.6% | Counted whole |
| Hill City | 938 | +7.0% | 0.8% |
| Wall | 668 | −3.9% | 0.6% |
| New Underwood | 594 | −0.7% | 0.5% |
| Keystone | 268 | +7.6% | 0.2% |
| Quinn | 61 | Level | Under 0.1% |
| Wasta | 60 | −4.8% | Under 0.1% |
Places in Pennington County with a city page: 1 of 1
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 Pennington County is counted whole, so it has no share.
Pennington County, Homes
Homes in Pennington County
Of Pennington County's 50,655 homes, 62% are detached houses, against 67% across South Dakota; 17% are in buildings of five or more homes. Half of its homes were built before 1982, close to South Dakota's 1979: 22% date from before 1960 and 29% from 2000 or later. 69% 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 | Pennington County | South Dakota |
|---|---|---|
| Housing units | 50,655 | 402,364 |
| Detached houses | 62% | 67% |
| In buildings of 5 or more | 17% | 16% |
| Mobile homes | 10% | 8% |
| Built before 1960 | 22% | 29% |
| Built since 2000 | 29% | 28% |
| Middle year built | 1982 | 1979 |
| Owner-occupied | 69% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.