Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Sumter County, South Carolina
EPA puts Sumter County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 11.9% of 42 (2008 to 2017, laboratory totals) reached 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
11.9%
7.5 pts below SC
- Sumter
- 11.9%
- SC
- 19.4%
42 tests, 2008 to 2017
Median result
1.3pCi/L
Below action level
- Sumter
- 1.3 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
42
24th of 24 by tests
- Sumter
- 42
- Greenville
- 12,004
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in SC
13 of 24
Middle half
- Sumter
- 11.9%
- Oconee
- 42.6%
By share, of 24 with 30+ tests
Read a result for Sumter County
Starts at Sumter County's median, 1.3 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.3 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Sumter County's median reported result, 2008 to 2017.
The data
Sumter County, At a glance
Sumter County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Sumter County, 2008 to 2017, laboratory
Under 2 pCi/L: 74%2 to 4 pCi/L: 14%4 pCi/L and above: 12%
Of 42 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 31 | 73.8% |
| 2 to 4 pCi/L | 6 | 14.3% |
| 4 pCi/L and above | 5 | 11.9% |
What these figures count
These are the 42 tests reported to CDC for Sumter 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).
Sumter County, Compared
Sumter County radon figures, compared
Calculated by Radon411Sumter County reports fewer high tests than South Carolina overall. 11.9% of its 42 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 7.5 points below the 19.4% pooled from 46 South Carolina counties.
Ordered from highest share down, it comes 13th of 24 South Carolina counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Sumter County sits 23.8 points below it.
Next door, the shares run from 0.0% in Florence County to 5.0% in Kershaw County, with Kershaw County, Richland County and Florence County below Sumter County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 11.9% share point the same way here.
Half the tests came in under 1.3 pCi/L and half over it; the single highest reached 7.5 pCi/L. The rest split 73.8% under 2 pCi/L and 14.3% from 2 to 4 (South Carolina: 57.4% and 23.1%).
CDC's ten-year totals for Sumter County went from 64 tests (2005 to 2014) to 42 (2008 to 2017), the share going from 3.1% to 11.9%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Sumter County, Geology
The ground under Sumter County
PredictedUSGS's geologic map puts all of Sumter County's mapped land in one class: low radon potential. All of it lies in the area the map calls Upper and Middle Coastal Plain, to which USGS gives a radon index of 8, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Upper and Middle Coastal Plain | Tertiary coastal plain sandy and silty sediments and marsh deposits. | Low | 8 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Sumter County beside the ground around it
Across South Carolina 0.2% of the land is rated high; none of Sumter County's is. Of the 6 counties that border it, 2 have more moderate-potential ground, Kershaw County the most at 11.3%.
The map rates the ground, not the air in any home.
Local help
Sumter County, Local resources
Radon testing and mitigation in Sumter County
- South Carolina Radon ProgramSouth Carolina Radon Program, run by South Carolina Department of Environmental Services, offers free or discounted test kits, and answers questions about testing and mitigation in South Carolina.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The South Carolina Radon Program offers free short-term radon test kits to South Carolina homeowners, subject to availability.
- Compare kits
- Professionals in South Carolina2 professionals are listed in South Carolina.
What South Carolina's program says
- Phone
- 1-800-768-0362
- radon@des.sc.gov
What it means
Sumter County, Questions
Questions about radon in Sumter County
Are radon levels high in Sumter County?
Over the 2008 to 2017 laboratory totals, 11.9% of the radon tests reported to CDC for Sumter County, South Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.3 pCi/L. Of 24 South Carolina counties with 30 or more tests for the same period, 12 reported a higher share; pooled, the state comes to 19.4%.
Which counties border Sumter County?
Sumter County borders 6 counties: Clarendon County, Lee County, Calhoun County, Richland County, Kershaw County and Florence County.
Products
Sumter County, Products
Testing a home in Sumter County
In Sumter County, 11.9% of 42 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 19.4% pooled across South Carolina. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Sumter County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
MonitorAEGTEST
HOUND-3699 radon monitor with a 2.1-inch touchscreen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
First reading: Within 1 hour
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Sumter County, Bordering counties
Counties bordering Sumter County
Calculated by Radon411- Radon levels in Kershaw CountyEPA zone 3
5.0%at or above 4 pCi/L
Median 0.7 pCi/L · 60 tests · 6.9 points below Sumter County
- Radon levels in Richland CountyEPA zone 3
4.9%at or above 4 pCi/L
Median 0.7 pCi/L · 671 tests · 7.0 points below Sumter County
- Radon levels in Clarendon CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.8 pCi/L · 3 tests · 11.9 points below Sumter County
- Radon levels in Lee CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.1 pCi/L · 3 tests · 11.9 points below Sumter County
- Radon levels in Calhoun CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.6 pCi/L · 11 tests · 11.9 points below Sumter County
- Radon levels in Florence CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.7 pCi/L · 59 tests · 11.9 points below Sumter County
Sumter County, Cities and towns
Cities and towns in Sumter County
Sumter County's population has barely moved since 2020: 105,067 residents on July 1, 2025 against 105,409 then, by the Census Bureau's estimates. That works out to 158 people per square mile of land. Its largest town, Sumter, has 43,094 residents, 41.0% of the total. Together its 3 incorporated places hold 42.0% of those residents; the other 58.0% live outside any of them. Reported testing is thin here: 42 tests over 2008 to 2017, or 0.4 for every 1,000 residents (2025 estimate), where South Carolina as a whole comes to 4.8.
From Sumter to Pinewood, CDC publishes no figure by town: each reads Sumter County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Sumter | 43,094 | −0.8% | 41.0% |
| Mayesville | 554 | +0.4% | 0.5% |
| Pinewood | 498 | −0.6% | 0.5% |
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).
Sumter County, Homes
Homes in Sumter County
Of Sumter County's 47,288 homes, 67% are detached houses, against 64% across South Carolina; 19% are mobile homes. Half of its homes were built before 1987, close to South Carolina's 1991: 12% date from before 1960 and 25% from 2000 or later. 67% of occupied homes are lived in by their owner (South Carolina: 71%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Sumter County | South Carolina |
|---|---|---|
| Housing units | 47,288 | 2,401,638 |
| Detached houses | 67% | 64% |
| In buildings of 5 or more | 7% | 13% |
| Mobile homes | 19% | 15% |
| Built before 1960 | 12% | 13% |
| Built since 2000 | 25% | 35% |
| Middle year built | 1987 | 1991 |
| Owner-occupied | 67% | 71% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.