Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
Locations and reports
Radon Levels in Loudoun County, Virginia
EPA puts Loudoun County in Zone 2, its middle radon zone, and 27.4% of its 4,457 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
27.4%
3.0 pts below VA
- Loudoun
- 27.4%
- Virginia
- 30.4%
4,457 tests, 2008 to 2017
Median result
1.8pCi/L
Below action level
- Loudoun
- 1.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
4,457
2nd of 84 by tests
- Loudoun
- 4,457
- Fairfax
- 8,657
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 Virginia
59 of 84
Middle half
- Loudoun
- 27.4%
- Russell
- 67.3%
By share, of 84 with 30+ tests
Read a result for Loudoun County
Starts at Loudoun 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. Loudoun County's median reported result, 2008 to 2017.
The data
Loudoun County, At a glance
Loudoun County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Loudoun County is a
USGS geologic potential: Moderate across 99% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Loudoun County, 2008 to 2017, laboratory
Under 2 pCi/L: 52%2 to 4 pCi/L: 21%4 pCi/L and above: 27%
Of 4,457 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 2,304 | 51.7% |
| 2 to 4 pCi/L | 933 | 20.9% |
| 4 pCi/L and above | 1,220 | 27.4% |
What these figures count
These are the 4,457 tests reported to CDC for Loudoun 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).
Loudoun County, Compared
Loudoun County radon figures, compared
Calculated by Radon411Loudoun County's 4,457 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.8 pCi/L and a maximum of 159.3 pCi/L, and 27.4% reached 4 pCi/L. Virginia as a whole (131 Virginia counties, pooled) comes to 30.4%: 3.0 points higher than here.
Among its state's counties it ranks 59th of 84 Virginia counties with 30 or more tests for the same period. Statewide for the same period, Russell County reported the highest share (67.3%) and Norfolk city the lowest (2.7%).
Below the action level, 2,304 tests (51.7%) came in under 2 pCi/L, against 44.7% statewide, and 933 tests (20.9%) fell between 2 and 4, against 24.9% statewide. CDC's ten-year totals for Loudoun County went from 3,140 tests (2005 to 2014) to 4,457 (2008 to 2017), the share going from 26.8% to 27.4%.
EPA's 1993 zone map puts Loudoun County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 99% of the county's land moderate radon potential.
Next door, the shares run from 18.0% in Montgomery County, MD to 56.0% in Washington County, MD, with Fairfax County and Montgomery County, MD below Loudoun County.
CDC also counts 414 tests taken after mitigation in Loudoun 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.
Loudoun County, Geology
The ground under Loudoun County
PredictedMost of the ground under Loudoun County is one class on USGS's geologic map: 98.7% of its land is moderate radon potential, with 1.3% high. The map puts 53.6% of Loudoun County in the area it calls Blue Ridge and 45.1% in Mesozoic Basins, with one smaller area 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 |
|---|---|---|---|---|
| Blue Ridge | Granite, pegmatite, monazite, schist, and gneiss. | Moderate | 10 | 53.6% |
| Mesozoic Basins | Sandstone, siltstone and lacustrine black shale. | Moderate | 11 | 45.1% |
| Valley and Ridge | Cambrian dolomite, limestone, shale, and sandstone, Silurian-Ordovician limestone, dolomite, shale, and sandstone, Mississippian-Devonian sandstone, shale, limestone, gypsum, and coal. | High | 15 | 0.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Loudoun County beside the ground around it
Virginia as a whole has more high-potential ground than Loudoun County: 47.9% of its land, against 1.3% here. Every one of the 8 counties that border it has more high-potential ground, Jefferson County, WV the most at 95.7%.
The map rates the ground, not the air in any home.
Local help
Loudoun County, Local resources
Radon testing and mitigation in Loudoun County
- VDH Radon ProgramVDH Radon Program answers questions about testing, mitigation and the rules in Virginia.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Virginia2 professionals are listed in Virginia.
What Virginia's program says
- Phone
- (804) 864-8161
- Radon@vdh.virginia.gov
- Licensing of radon professionals
The Code of Virginia requires that Radon testers and mitigators be currently certified by either the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB).
What it means
Loudoun County, Questions
Questions about radon in Loudoun County
Are radon levels high in Loudoun County?
Over the 2008 to 2017 laboratory totals, 27.4% of the radon tests reported to CDC for Loudoun County, Virginia were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.8 pCi/L. Of 84 Virginia counties with 30 or more tests for the same period, 58 reported a higher share; pooled, the state comes to 30.4%.
Which counties border Loudoun County?
Loudoun County borders 8 counties: Clarke County, VA, Jefferson County, WV, Fairfax County, VA, Montgomery County, MD, Prince William County, VA, Fauquier County, VA, Washington County, MD and Frederick County, MD.
Products
Loudoun County, Products
Testing a home in Loudoun County
In Loudoun County, 27.4% of 4,457 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 30.4% pooled across Virginia. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Loudoun 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
Corentium Home 2 battery digital radon monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Screen, app
Method: Alpha spectrometry
Readings: Every 60 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Loudoun County, Bordering counties
Counties bordering Loudoun County
Calculated by Radon411- Radon levels in Washington County, MDEPA zone 1
56.0%at or above 4 pCi/L
Median 5.2 pCi/L · 1,259 tests · 28.6 points above Loudoun County
- Radon levels in Jefferson County, WVEPA zone 1
53.2%at or above 4 pCi/L
Median 4.4 pCi/L · 898 tests · 25.8 points above Loudoun County
- Radon levels in Clarke County, VAEPA zone 1
47.7%at or above 4 pCi/L
Median 3.5 pCi/L · 350 tests · 20.3 points above Loudoun County
31.7%at or above 4 pCi/L
Median 2.3 pCi/L · 4,441 tests · 4.3 points above Loudoun County
- Radon levels in Fauquier County, VAEPA zone 2
30.2%at or above 4 pCi/L
Median 2.5 pCi/L · 1,199 tests · 2.8 points above Loudoun County
- Radon levels in Frederick County, MDEPA zone 1
28.1%at or above 4 pCi/L
Median 1.5 pCi/L · 3,933 tests · 0.7 points above Loudoun 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 · 8.7 points below Loudoun County
- Radon levels in Montgomery County, MDEPA zone 1
18.0%at or above 4 pCi/L
Median 1.3 pCi/L · 10,969 tests · 9.4 points below Loudoun County
Loudoun County, Cities and towns
Cities and towns in Loudoun County
Loudoun County is growing: the Census Bureau puts it at 449,749 residents on July 1, 2025, up 6.4% from 422,693 in 2020. That works out to 872 people per square mile of land. No town dominates: Leesburg, the largest, has 49,917 residents, 11.1% of the total. Testing is reported here more often than across the state: CDC's 4,457 reported tests for 2008 to 2017 come to 9.9 for every 1,000 residents (2025 estimate), against 6.0 for Virginia.
From Leesburg to Hillsboro, CDC publishes no figure by town: each reads Loudoun County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Leesburg | 49,917 | +3.1% | 11.1% |
| Herndonextends beyond Loudoun County | 25,506 | +3.7% | Counted whole |
| Purcellville | 8,890 | −0.6% | 2.0% |
| Lovettsville | 2,708 | Level | 0.6% |
| Round Hill | 702 | +0.3% | 0.2% |
| Middleburg | 699 | +3.9% | 0.2% |
| Hamilton | 608 | −1.8% | 0.1% |
| Hillsboro | 112 | −3.4% | Under 0.1% |
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 Loudoun County is counted whole, so it has no share.
Loudoun County, Homes
Homes in Loudoun County
Fewer than six in ten of Loudoun County's 144,804 homes are detached houses (52%, against 61% across Virginia); the rest are attached, in shared buildings or mobile. Much of Loudoun County is recent building: 55% of its homes have gone up since 2000 and the middle year built is 2002, against 1984 for Virginia. Owners live in 78% of the occupied homes (Virginia: 67%), so for most households a test and a fix are their own to order.
| Homes | Loudoun County | Virginia |
|---|---|---|
| Housing units | 144,804 | 3,654,784 |
| Detached houses | 52% | 61% |
| In buildings of 5 or more | 16% | 19% |
| Mobile homes | 1% | 4% |
| Built before 1960 | 4% | 19% |
| Built since 2000 | 55% | 25% |
| Middle year built | 2002 | 1984 |
| Owner-occupied | 78% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.