Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Clarke County, Virginia
EPA puts Clarke County in Zone 1, its highest radon zone, and high results are common there: 47.7% of the 350 radon tests reported to CDC (2008 to 2017, laboratory totals) came back 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
47.7%
17.3 pts above VA
- Clarke
- 47.7%
- Virginia
- 30.4%
350 tests, 2008 to 2017
Median result
3.5pCi/L
Below action level
- Clarke
- 3.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
350
36th of 84 by tests
- Clarke
- 350
- Fairfax
- 8,657
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Virginia
15 of 84
Top quarter
- Clarke
- 47.7%
- Russell
- 67.3%
By share, of 84 with 30+ tests
Read a result for Clarke County
Starts at Clarke County's median, 3.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.5 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Clarke County's median reported result, 2008 to 2017.
The data
Clarke County, At a glance
Clarke County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Clarke County in
USGS geologic potential: High across 83% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Clarke County, 2008 to 2017, laboratory
Under 2 pCi/L: 37%2 to 4 pCi/L: 15%4 pCi/L and above: 48%
Of 350 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 129 | 36.9% |
| 2 to 4 pCi/L | 54 | 15.4% |
| 4 pCi/L and above | 167 | 47.7% |
What these figures count
These are the 350 tests reported to CDC for Clarke 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).
Clarke County, Compared
Clarke County radon figures, compared
Calculated by Radon411In Clarke County, about 5 in 10 reported tests over the 2008 to 2017 laboratory totals (167 of 350) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 12.0 points higher. Across 131 Virginia counties pooled together, 30.4% of tests reached that level, so Clarke County runs 17.3 points above its state.
Of 6 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 4 a smaller one; the spread is 27.4% (Loudoun County) to 53.2% (Jefferson County, WV). By share, Clarke County is 15th of 84 Virginia counties with 30 or more tests for the same period.
Half the tests came in under 3.5 pCi/L and half over it; the single highest reached 60.4 pCi/L. Below the action level, 129 tests (36.9%) came in under 2 pCi/L, against 44.7% statewide, and 54 tests (15.4%) fell between 2 and 4, against 24.9% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 47.7% share point the same way here. USGS geology rates 83% of the county's land high radon potential. CDC also counts 18 tests taken after mitigation in Clarke County for the same period: tests in homes where a fix was already in.
CDC's ten-year totals for Clarke County went from 245 tests (2005 to 2014) to 350 (2008 to 2017), the share going from 51.0% to 47.7%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Clarke County, Geology
The ground under Clarke County
PredictedMost of the ground under Clarke County is one class on USGS's geologic map: 83.3% of its land is high radon potential, with 16.7% moderate. The map puts 83.3% of Clarke County in the area it calls Valley and Ridge and 16.7% in Blue Ridge. USGS gives the first a radon index of 15, 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 |
|---|---|---|---|---|
| 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 | 83.3% |
| Blue Ridge | Granite, pegmatite, monazite, schist, and gneiss. | Moderate | 10 | 16.7% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Clarke County beside the ground around it
Clarke County has more high-potential ground than Virginia as a whole: 83.3% of its land against 47.9%. Of the 6 counties that border it, 3 have more high-potential ground, Frederick County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Clarke County, Local resources
Radon testing and mitigation in Clarke 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
Clarke County, Questions
Questions about radon in Clarke County
Are radon levels high in Clarke County?
Over the 2008 to 2017 laboratory totals, 47.7% of the radon tests reported to CDC for Clarke County, Virginia were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.5 pCi/L. Of 84 Virginia counties with 30 or more tests for the same period, 14 reported a higher share; pooled, the state comes to 30.4%.
Which counties border Clarke County?
Clarke County borders 6 counties: Jefferson County, WV, Frederick County, VA, Loudoun County, VA, Warren County, VA, Berkeley County, WV and Fauquier County, VA.
Products
Clarke County, Products
Testing a home in Clarke County
In Clarke County, 47.7% of 350 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 30.4% pooled across Virginia. In Zone 1 the year-round level in Clarke 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
MonitorX-Sense
XR0A-iR Wi-Fi battery radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Wi-Fi
- Screen, app
Method: Alpha spectrometry
First reading: Within 24 hours
Short-term kitKidde
442020 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 3 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Clarke County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Clarke County
Explore
Clarke County, Bordering counties
Counties bordering Clarke County
Calculated by Radon411- Radon levels in Jefferson County, WVEPA zone 1
53.2%at or above 4 pCi/L
Median 4.4 pCi/L · 898 tests · 5.5 points above Clarke County
- Radon levels in Berkeley County, WVEPA zone 1
50.7%at or above 4 pCi/L
Median 4.0 pCi/L · 2,888 tests · 3.0 points above Clarke County
- Radon levels in Frederick County, VAEPA zone 1
44.1%at or above 4 pCi/L
Median 3.3 pCi/L · 2,451 tests · 3.6 points below Clarke County
- Radon levels in Warren County, VAEPA zone 1
36.9%at or above 4 pCi/L
Median 2.7 pCi/L · 536 tests · 10.8 points below Clarke 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 · 17.5 points below Clarke County
- Radon levels in Loudoun County, VAEPA zone 2
27.4%at or above 4 pCi/L
Median 1.8 pCi/L · 4,457 tests · 20.3 points below Clarke County
Clarke County, Cities and towns
Cities and towns in Clarke County
Clarke County is growing: the Census Bureau puts it at 15,609 residents on July 1, 2025, up 5.3% from 14,817 in 2020. That works out to 89 people per square mile of land. Its largest town, Berryville, has 4,828 residents, 30.9% of the total. Together its 2 incorporated places hold 36.0% of those residents; the other 64.0% live outside any of them. Testing is reported here more often than across the state: CDC's 350 reported tests for 2008 to 2017 come to 22.4 for every 1,000 residents (2025 estimate), against 6.0 for Virginia.
From Berryville to Boyce, CDC publishes no figure by town: each reads Clarke County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Berryville | 4,828 | +5.2% | 30.9% |
| Boyce | 794 | +5.4% | 5.1% |
2 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).
Clarke County, Homes
Homes in Clarke County
Clarke County is a place of houses on their own lots: 89% of its 6,478 homes are detached single-family houses, against 61% across Virginia. Half of its homes were built before 1980, close to Virginia's 1984: 29% date from before 1960 and 25% from 2000 or later. Owners live in 82% of the occupied homes (Virginia: 67%), so for most households a test and a fix are their own to order.
| Homes | Clarke County | Virginia |
|---|---|---|
| Housing units | 6,478 | 3,654,784 |
| Detached houses | 89% | 61% |
| In buildings of 5 or more | 4% | 19% |
| Mobile homes | 1% | 4% |
| Built before 1960 | 29% | 19% |
| Built since 2000 | 25% | 25% |
| Middle year built | 1980 | 1984 |
| Owner-occupied | 82% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.