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 Lyman County, South Dakota
EPA puts Lyman 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
66.7%
Hughes County
- Hughes
- 66.7%
- Brule
- 62.5%
2 of 10 neighbours have 30+ tests, 2006 to 2015
Nearest county
66.7%
Hughes County, 35 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
- Lyman
- 100.0%
- SD
- 99.0%
Share of land USGS rates moderate or high potential
Tests reported
5
Too few for a share
- Lyman
- 5
- Needed
- 30
2007 to 2016, 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 Lyman 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
Lyman County, At a glance
Lyman County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Lyman County in
USGS geologic potential: High across 56% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Lyman County, 2008 to 2017, laboratory
CDC holds 2 reported tests for Lyman County over the 2008 to 2017 laboratory totals, with a median of 22.1 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Lyman County beside the counties around it is how this page reads it.
What these figures count
Only 2 tests were reported to CDC for Lyman 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).
Lyman County, Compared
Lyman County radon figures, compared
Calculated by Radon411CDC's largest figure for Lyman County rests on 5 tests over the 2007 to 2016 laboratory totals, 5 of them at or above 4 pCi/L, so each test moves its share by 20.0 points and no rank or comparison is drawn from it. Results reached as high as 31.7 pCi/L, with a middle value of 20.0 pCi/L.
Of the counties bordering it, 2 have a figure over the 2006 to 2015 laboratory totals: Hughes County reported the largest share at or above 4 pCi/L, 66.7%, and Brule County the smallest, 62.5%. Farther out, Beadle County (86 miles away) at 63.0%, Davison County (86 miles away) at 47.9% and Edmunds County (110 miles away) at 61.8% have figures too. 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 Lyman County in Zone 1, the map's highest label: a predicted county average above 4 pCi/L. USGS geology rates 56% of the county's land high radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Lyman County, Geology
The ground under Lyman County
PredictedUSGS's geologic map splits Lyman County: 55.7% of its land is high radon potential and 44.3% moderate. The map puts 55.7% of Lyman County in the area it calls Missouri Coteau/James River Lowland/Coteau des Prairies and 44.3% in Pierre Hills. USGS gives the first a radon index of 14, 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 |
|---|---|---|---|---|
| Missouri Coteau/James River Lowland/Coteau des Prairies | Glacial drift derived largely from Cretaceous marine shale. | High | 14 | 55.7% |
| Pierre Hills | Pierre Shale and Fox Hills sandstone. | Moderate | 10 | 44.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Lyman County beside the ground around it
On high-potential ground Lyman County is close to South Dakota as a whole: 55.7% of its land against 56.7%. Of the 10 counties that border it, 5 have more high-potential ground, Brule County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Lyman County, Local resources
Radon testing and mitigation in Lyman 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
Lyman County, Questions
Questions about radon in Lyman County
Are radon levels high in Lyman County?
Over the 2008 to 2017 laboratory totals, 100.0% of the radon tests reported to CDC for Lyman County, South Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 22.1 pCi/L. Of the counties bordering it, 2 have a figure over the 2006 to 2015 laboratory totals: Hughes County reported the largest share at or above 4 pCi/L, 66.7%, and Brule County the smallest, 62.5%.
Which counties border Lyman County?
Lyman County borders 10 counties: Hughes County, Buffalo County, Brule County, Hyde County, Tripp County, Jones County, Mellette County, Gregory County, Stanley County and Charles Mix County.
Products
Lyman County, Products
Testing a home in Lyman County
No CDC figure names Lyman County; the nearest county with one, Hughes County (35 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 1 the year-round level in Lyman 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
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
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
Lyman County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Lyman County
Explore
Lyman County, Bordering counties
Counties bordering Lyman County
Calculated by Radon411- Radon levels in Buffalo CountyEPA zone 1
100.0%at or above 4 pCi/L
Median 10.9 pCi/L · 1 test
- Radon levels in Jones CountyEPA zone 2
100.0%at or above 4 pCi/L
Median 26.4 pCi/L · 5 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 Hyde CountyEPA zone 1
80.0%at or above 4 pCi/L
Median 4.9 pCi/L · 5 tests
- Radon levels in Gregory CountyEPA zone 2
80.0%at or above 4 pCi/L
Median 6.7 pCi/L · 10 tests
- Radon levels in Hughes CountyEPA zone 1
66.7%at or above 4 pCi/L
Median 5.5 pCi/L · 30 tests
- Radon levels in Charles Mix CountyEPA zone 1
63.6%at or above 4 pCi/L
Median 6.1 pCi/L · 11 tests
- Radon levels in Brule CountyEPA zone 1
62.5%at or above 4 pCi/L
Median 6.3 pCi/L · 32 tests
- Radon levels in Tripp CountyEPA zone 2
57.1%at or above 4 pCi/L
Median 4.2 pCi/L · 7 tests
- Radon levels in Mellette CountyEPA zone 2
No CDC figure for 2006 to 2015; its page reads it against its own neighbours.
Lyman County, Cities and towns
Cities and towns in Lyman County
Lyman County's population has barely moved since 2020: 3,694 residents on July 1, 2025 against 3,697 then, by the Census Bureau's estimates. Spread over its land, that is 2.2 people to the square mile. No town dominates: Presho, the largest, has 463 residents, 12.5% of the total. Together its 4 incorporated places hold 34.2% of those residents; the other 65.8% live outside any of them. Reported testing is thin here: 5 tests over 2007 to 2016, or 1.4 for every 1,000 residents (2025 estimate), where South Dakota as a whole comes to 5.7.
From Presho to Reliance, CDC publishes no figure by town: each reads Lyman County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Presho | 463 | −2.1% | 12.5% |
| Oacoma | 391 | +1.3% | 10.6% |
| Kennebec | 282 | +1.8% | 7.6% |
| Reliance | 127 | Level | 3.4% |
4 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).
Lyman County, Homes
Homes in Lyman County
Lyman County is a place of houses on their own lots: 81% of its 1,561 homes are detached single-family houses, against 67% across South Dakota. Half of its homes were built before 1974, close to South Dakota's 1979: 28% date from before 1960 and 16% from 2000 or later. 72% 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 | Lyman County | South Dakota |
|---|---|---|
| Housing units | 1,561 | 402,364 |
| Detached houses | 81% | 67% |
| In buildings of 5 or more | 3% | 16% |
| Mobile homes | 11% | 8% |
| Built before 1960 | 28% | 29% |
| Built since 2000 | 16% | 28% |
| Middle year built | 1974 | 1979 |
| Owner-occupied | 72% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.