Short-term kit
Radon Short Term Test Kit short-term charcoal radon test kit, lab fee included
- Lab fee included
Method: Charcoal
In home: 2 to 7 days
Locations and reports
Radon Levels in Marion County, South Carolina
EPA puts Marion County in Zone 3, its lowest radon zone, and only 9 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
0.9%
Horry County
- Horry
- 0.9%
- Florence
- 0.0%
2 of 5 neighbours have 30+ tests, 2008 to 2017
Nearest county
0.0%
Florence County, 20 miles
- Florence
- 0.0%
- SC
- 19.4%
Share at 4+ pCi/L, 59 tests, 2008 to 2017
Ground above low
None
18.5 pts below SC
- Marion
- 0.0%
- SC
- 18.5%
Share of land USGS rates moderate or high potential
Tests reported
9
Too few for a share
- Marion
- 9
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Read a result for Marion 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
Marion County, At a glance
Marion 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 Marion County, 2008 to 2017, laboratory
CDC holds 9 reported tests for Marion County over the 2008 to 2017 laboratory totals, with a median of 0.9 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Marion County beside the counties around it is how this page reads it.
What these figures count
Only 9 tests were reported to CDC for Marion 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).
Marion County, Compared
Marion County radon figures, compared
Calculated by Radon411CDC's largest figure for Marion County rests on 9 tests over the 2008 to 2017 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 11.1 points and no rank or comparison is drawn from it. Results reached as high as 1.3 pCi/L, with a middle value of 0.9 pCi/L.
Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Horry County reported the largest share at or above 4 pCi/L, 0.9%, and Florence County the smallest, 0.0%. Farther out, Sumter County (60 miles away) at 11.9%, Berkeley County (70 miles away) at 4.0% and Kershaw County (73 miles away) at 5.0% have figures too. Pooled across 46 South Carolina counties, 19.4% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Oconee County reported the highest share (42.6%) and Florence County the lowest (0.0%). EPA's 1993 map puts Marion County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 100% of the county's land low radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Marion County, Geology
The ground under Marion County
PredictedUSGS's geologic map puts all of Marion County's mapped land in one class: low radon potential. The map puts 71.0% of Marion County in the area it calls Upper and Middle Coastal Plain and 29.0% in Lower Coastal Plain. USGS gives the first a radon index of 8 and the second 7, both 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 | 71.0% |
| Lower Coastal Plain | Dune, beach, and marine sediments. | Low | 7 | 29.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Marion County beside the ground around it
Across South Carolina 0.2% of the land is rated high; none of Marion County's is. None of the 5 counties that border it has any moderate-potential ground either.
The map rates the ground, not the air in any home.
Local help
Marion County, Local resources
Radon testing and mitigation in Marion 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
Marion County, Questions
Questions about radon in Marion County
Are radon levels high in Marion County?
Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Marion County, South Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Horry County reported the largest share at or above 4 pCi/L, 0.9%, and Florence County the smallest, 0.0%.
Which counties border Marion County?
Marion County borders 5 counties: Florence County, Dillon County, Horry County, Williamsburg County and Georgetown County.
Products
Marion County, Products
Testing a home in Marion County
No CDC figure names Marion County; the nearest county with one, Florence County (20 miles away), reported 0.0% 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. 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 Marion 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
MonitorX-Sense
XR0B-SR battery digital radon monitor with an alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Marion County, Bordering counties
Counties bordering Marion County
Calculated by Radon411- Radon levels in Horry CountyEPA zone 3
0.9%at or above 4 pCi/L
Median 0.6 pCi/L · 106 tests
- Radon levels in Florence CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.7 pCi/L · 59 tests
- Radon levels in Dillon CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.3 pCi/L · 18 tests
- Radon levels in Williamsburg CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.6 pCi/L · 14 tests
- Radon levels in Georgetown CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.1 pCi/L · 29 tests
Marion County, Cities and towns
Cities and towns in Marion County
About 28,242 people live in Marion County by the Census Bureau's estimate for July 1, 2025, 846 fewer than in 2020 (−2.9%). That works out to 58 people per square mile of land. Its largest town, Marion, has 6,028 residents, 21.3% of the total. Together its 4 incorporated places hold 36.2% of those residents; the other 63.8% live outside any of them. Reported testing is thin here: 9 tests over 2008 to 2017, or 0.3 for every 1,000 residents (2025 estimate), where South Carolina as a whole comes to 4.8.
From Marion to Sellers, CDC publishes no figure by town: each reads Marion County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Marion | 6,028 | −5.4% | 21.3% |
| Mullins | 3,838 | −4.4% | 13.6% |
| Nichols | 222 | −3.5% | 0.8% |
| Sellers | 146 | −1.4% | 0.5% |
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).
Marion County, Homes
Homes in Marion County
Of Marion County's 14,418 homes, 56% are detached houses, against 64% across South Carolina; 36% are mobile homes. The homes are older than South Carolina's as a whole: half were built before 1983 (1991 for South Carolina), and 19% date from before 1960. 62% 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 | Marion County | South Carolina |
|---|---|---|
| Housing units | 14,418 | 2,401,638 |
| Detached houses | 56% | 64% |
| In buildings of 5 or more | 2% | 13% |
| Mobile homes | 36% | 15% |
| Built before 1960 | 19% | 13% |
| Built since 2000 | 19% | 35% |
| Middle year built | 1983 | 1991 |
| Owner-occupied | 62% | 71% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.