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 Charles County, Maryland
EPA puts Charles County in Zone 2, its middle radon zone, and 24.1% of its 477 reported radon tests (2008 to 2017, laboratory totals) were 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
24.1%
0.2 pts above MD
- Charles
- 24.1%
- Maryland
- 23.9%
477 tests, 2008 to 2017
Median result
1.8pCi/L
Below action level
- Charles
- 1.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
477
14th of 19 by tests
- Charles
- 477
- Montgomery
- 10,969
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 Maryland
10 of 19
Middle half
- Charles
- 24.1%
- Washington
- 56.0%
By share, of 19 with 30+ tests
Read a result for Charles County
Starts at Charles County's median, 1.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.8 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. Charles County's median reported result, 2008 to 2017.
The data
Charles County, At a glance
Charles County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Charles County is a
USGS geologic potential: Moderate across 94% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Charles County, 2008 to 2017, laboratory
Under 2 pCi/L: 54%2 to 4 pCi/L: 22%4 pCi/L and above: 24%
Of 477 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 255 | 53.5% |
| 2 to 4 pCi/L | 107 | 22.4% |
| 4 pCi/L and above | 115 | 24.1% |
What these figures count
These are the 477 tests reported to CDC for Charles 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).
Charles County, Compared
Charles County radon figures, compared
Calculated by Radon411Charles County's 477 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.8 pCi/L and a maximum of 63.6 pCi/L, and 24.1% reached 4 pCi/L. Maryland as a whole (24 Maryland counties, pooled) comes to 23.9%: 0.2 points lower than here.
Among its state's counties it ranks 10th of 19 Maryland counties with 30 or more tests for the same period. Statewide for the same period, Washington County reported the highest share (56.0%) and Wicomico County the lowest (0.0%).
Below the action level, 255 tests (53.5%) came in under 2 pCi/L, against 56.6% statewide, and 107 tests (22.4%) fell between 2 and 4, against 19.5% statewide. CDC's ten-year totals for Charles County went from 351 tests (2005 to 2014) to 477 (2008 to 2017), the share going from 24.2% to 24.1%.
EPA's 1993 zone map puts Charles County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 94% of the county's land moderate radon potential.
Next door, the shares run from 18.7% in Fairfax County, VA to 30.2% in Calvert County, with St. Mary's County, Prince George's County and Fairfax County, VA below Charles County.
CDC also counts 42 tests taken after mitigation in Charles 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.
Charles County, Geology
The ground under Charles County
PredictedUSGS's geologic map puts all of Charles County's mapped land in one class: moderate radon potential. 93.7% of it lies in the area the map calls Western Shore, to which USGS gives a radon index of 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Western Shore | Cretaceous, Quaternary, minor Tertiary gravel, sand, silt, clay. | Moderate | 10 | 93.7% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Charles County beside the ground around it
Across Maryland 36.7% of the land is rated high; none of Charles County's is. Of the 4 counties that border it, 3 have more high-potential ground, Calvert County the most at 88.3%.
The map rates the ground, not the air in any home.
Local help
Charles County, Local resources
Radon testing and mitigation in Charles County
- Maryland's radon programMaryland Department of HealthMaryland's radon program offers free or discounted test kits, and answers questions about testing and mitigation in Maryland.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Maryland residents may be eligible for a free radon test kit.
- Compare kits
- Professionals in Maryland5 professionals are listed in Maryland.
What Maryland's program says
- Phone
- 1-866-703-3266
What it means
Charles County, Questions
Questions about radon in Charles County
Are radon levels high in Charles County?
Over the 2008 to 2017 laboratory totals, 24.1% of the radon tests reported to CDC for Charles County, Maryland were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.8 pCi/L. Of 19 Maryland counties with 30 or more tests for the same period, 9 reported a higher share; pooled, the state comes to 23.9%.
Which counties border Charles County?
Charles County borders 4 counties: Calvert County, MD, Prince George's County, MD, St. Mary's County, MD and Fairfax County, VA.
Products
Charles County, Products
Testing a home in Charles County
In Charles County, 24.1% of 477 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 23.9% pooled across Maryland. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Charles County; a long-term test tells the year-round average.
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
Monitor
EcoBlu plug-in digital radon monitor with a display
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Charles County, Bordering counties
Counties bordering Charles County
Calculated by Radon411- Radon levels in Calvert County, MDEPA zone 1
30.2%at or above 4 pCi/L
Median 2.0 pCi/L · 1,205 tests · 6.1 points above Charles County
- Radon levels in St. Mary's County, MDEPA zone 2
20.9%at or above 4 pCi/L
Median 1.8 pCi/L · 636 tests · 3.2 points below Charles County
19.0%at or above 4 pCi/L
Median 1.4 pCi/L · 1,603 tests · 5.1 points below Charles County
- Radon levels in Fairfax County, VAEPA zone 1
18.7%at or above 4 pCi/L
Median 1.5 pCi/L · 8,657 tests · 5.4 points below Charles County
Charles County, Cities and towns
Cities and towns in Charles County
Charles County is growing: the Census Bureau puts it at 176,593 residents on July 1, 2025, up 5.9% from 166,734 in 2020. That works out to 386 people per square mile of land. No town dominates: La Plata, the largest, has 12,137 residents, 6.9% of the total. Together its 3 incorporated places hold 9.3% of those residents; the other 90.7% live outside any of them. Reported testing is thin here: 477 tests over 2008 to 2017, or 2.7 for every 1,000 residents (2025 estimate), where Maryland as a whole comes to 7.7.
From La Plata to Port Tobacco Village, CDC publishes no figure by town: each reads Charles County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| La Plata | 12,137 | +18.9% | 6.9% |
| Indian Head | 4,202 | +8.0% | 2.4% |
| Port Tobacco Village | 23 | +9.5% | Under 0.1% |
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).
Charles County, Homes
Homes in Charles County
Of Charles County's 63,053 homes, 71% are detached houses, against 51% across Maryland; 8% are in buildings of five or more homes. Much of Charles County is recent building: 32% of its homes have gone up since 2000 and the middle year built is 1990, against 1979 for Maryland. Owners live in 81% of the occupied homes (Maryland: 67%), so for most households a test and a fix are their own to order.
| Homes | Charles County | Maryland |
|---|---|---|
| Housing units | 63,053 | 2,545,532 |
| Detached houses | 71% | 51% |
| In buildings of 5 or more | 8% | 23% |
| Mobile homes | 1% | 1% |
| Built before 1960 | 9% | 27% |
| Built since 2000 | 32% | 20% |
| Middle year built | 1990 | 1979 |
| Owner-occupied | 81% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.