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Radon Levels in Frederick County, Virginia

EPA puts Frederick County in Zone 1, its highest radon zone, and high results are common there: 44.1% of the 2,451 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    44.1%

    13.7 pts above VA

    Frederick
    44.1%
    Virginia
    30.4%

    2,451 tests, 2008 to 2017

  • Median result

    3.3pCi/L

    Below action level

    Frederick
    3.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    2,451

    5th of 84 by tests

    Frederick
    2,451
    Fairfax
    8,657

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Virginia

    19 of 84

    Top quarter

    Frederick
    44.1%
    Russell
    67.3%

    By share, of 84 with 30+ tests

Read a result for Frederick County

Starts at Frederick County's median, 3.3 pCi/L

3.3pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 3.3 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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. Frederick County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Frederick County, At a glance

Frederick County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Frederick County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: High across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Frederick County, 2008 to 2017, laboratory

Reported results by concentration band, Frederick County, 2008 to 2017, laboratory
Under 2 pCi/L: 37%2 to 4 pCi/L: 19%4 pCi/L and above: 44%

Of 2,451 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Frederick County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L89736.6%
2 to 4 pCi/L47219.3%
4 pCi/L and above1,08244.1%
What these figures count

These are the 2,451 tests reported to CDC for Frederick 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).

How to read these figures

Frederick County, Compared

Frederick County radon figures, compared

Calculated by Radon411

In Frederick County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (1,082 of 2,451) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 8.4 points higher. Across 131 Virginia counties pooled together, 30.4% of tests reached that level, so Frederick County runs 13.7 points above its state.

Of 9 neighbours with a figure, 5 reported a larger share at or above 4 pCi/L and 4 a smaller one; the spread is 22.6% (Hardy County, WV) to 58.1% (Morgan County, WV). By share, Frederick County is 19th of 84 Virginia counties with 30 or more tests for the same period.

Half the tests came in under 3.3 pCi/L and half over it; the single highest reached 243.3 pCi/L. Below the action level, 897 tests (36.6%) came in under 2 pCi/L, against 44.7% statewide, and 472 tests (19.3%) fell between 2 and 4, against 24.9% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 44.1% share point the same way here. USGS geology rates 100% of the county's land high radon potential. CDC also counts 89 tests taken after mitigation in Frederick County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Frederick County went from 1,519 tests (2005 to 2014) to 2,451 (2008 to 2017), the share going from 47.9% to 44.1%.

Frederick County against Virginia, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Frederick County
Frederick County2,45144.1%3.3 pCi/LThis county
Virginia, pooled131 counties, pooled53,19930.4%Not pooled−13.7 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−8.4 points
Russell Countyhighest in the state4967.3%6.7 pCi/L+23.2 points
Norfolk citylowest in the state732.7%0.5 pCi/L−41.4 points
Morgan County, WVborders it24158.1%5.8 pCi/L+14.0 points
Jefferson County, WVborders it89853.2%4.4 pCi/L+9.1 points
Berkeley County, WVborders it2,88850.7%4.0 pCi/L+6.6 points
Clarke County, VAborders it35047.7%3.5 pCi/L+3.6 points
Winchester city, VAborders it77344.8%3.3 pCi/L+0.7 points
Hampshire County, WVborders it9038.9%2.8 pCi/L−5.2 points
Warren County, VAborders it53636.9%2.7 pCi/L−7.2 points
Shenandoah County, VAborders it39036.4%2.7 pCi/L−7.7 points
Hardy County, WVborders it5322.6%1.6 pCi/L−21.5 points
Where Frederick County's reported results fell, 2008 to 2017, laboratory, beside Virginia and the United States
ResultFrederick County testsFrederick County shareVirginia shareU.S. shareAgainst Virginia
Under 2 pCi/L89736.6%44.7%39.6%−8.1 points
2 to 4 pCi/L47219.3%24.9%24.7%−5.6 points
4 pCi/L and above1,08244.1%30.4%35.7%+13.7 points
Frederick County ranked among the 84 Virginia counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Waynesboro city14 of 8419648.5%3.8 pCi/L
Clarke County15 of 8435047.7%3.5 pCi/L
King George County16 of 8448845.5%3.6 pCi/L
Winchester city17 of 8477344.8%3.3 pCi/L
Grayson County18 of 844744.7%3.8 pCi/L
Frederick County19 of 842,45144.1%3.3 pCi/L
Madison County20 of 8418444.0%3.5 pCi/L
Rockingham County21 of 841,71443.9%3.3 pCi/L
Floyd County22 of 845442.6%3.3 pCi/L
Botetourt County23 of 8457542.1%3.3 pCi/L
Radford city24 of 849841.8%3.2 pCi/L
Frederick County ten-year laboratory totals, against Virginia's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestVirginia, pooledChange from the row before
2008 to 20172,45144.1%3.3 pCi/L243.3 pCi/L30.4%−1.4 points
2007 to 20162,19645.5%3.4 pCi/L243.3 pCi/L30.6%−1.4 points
2006 to 20151,85446.9%3.6 pCi/L243.3 pCi/L30.7%−1.0 points
2005 to 20141,51947.9%3.7 pCi/L243.3 pCi/L30.3%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Frederick County, Geology

The ground under Frederick County

Predicted

USGS's geologic map puts all of Frederick County's mapped land in one class: high radon potential. All of it lies in the area the map calls Valley and Ridge, to which USGS gives a radon index of 15, in the high band (12 to 17).

USGS's geologic areas under Frederick County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Valley and RidgeCambrian dolomite, limestone, shale, and sandstone, Silurian-Ordovician limestone, dolomite, shale, and sandstone, Mississippian-Devonian sandstone, shale, limestone, gypsum, and coal.High1599.8%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Frederick County beside the ground around it

Frederick County has more high-potential ground than Virginia as a whole: 100% of its land against 47.9%. Of the 9 counties that border it, none has as large a share of high-potential ground; Winchester city comes nearest at 100%.

Share of land by USGS radon potential: Frederick County, the 9 counties bordering it and Virginia
AreaEPA zoneLow potentialModerate potentialHigh potential
Frederick CountyZone 1NoneNone100%
Winchester cityZone 1NoneNone100%
Clarke CountyZone 1None16.7%83.3%
Berkeley County, WVZone 1NoneNone100%
Jefferson County, WVZone 1None4.3%95.7%
Morgan County, WVZone 1NoneNone100%
Hampshire County, WVZone 1NoneNone100%
Warren CountyZone 1None47.3%52.7%
Shenandoah CountyZone 1NoneNone100%
Hardy County, WVZone 1NoneNone100%
Virginia133 counties, pooled by land areaVaries20.6%30.0%47.9%

The map rates the ground, not the air in any home.

Local help

Frederick County, Local resources

Radon testing and mitigation in Frederick County

What Virginia's program says
Phone
(804) 864-8161
Email
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

Frederick County, Questions

Questions about radon in Frederick County

Are radon levels high in Frederick County?

Over the 2008 to 2017 laboratory totals, 44.1% of the radon tests reported to CDC for Frederick County, Virginia were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.3 pCi/L. Of 84 Virginia counties with 30 or more tests for the same period, 18 reported a higher share; pooled, the state comes to 30.4%.

Which counties border Frederick County?

Frederick County borders 9 counties: Winchester city, VA, Clarke County, VA, Berkeley County, WV, Jefferson County, WV, Morgan County, WV, Hampshire County, WV, Warren County, VA, Shenandoah County, VA and Hardy County, WV.

Products

Frederick County, Products

Testing a home in Frederick County

In Frederick County, 44.1% of 2,451 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 Frederick 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

Frederick County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Frederick County

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Frederick County, Bordering counties

Counties bordering Frederick County

Calculated by Radon411

Frederick County, Cities and towns

Cities and towns in Frederick County

Frederick County is growing: the Census Bureau puts it at 99,955 residents on July 1, 2025, up 8.8% from 91,891 in 2020. That works out to 242 people per square mile of land. No town dominates: Stephens City, the largest, has 2,207 residents, 2.2% of the total. Together its 2 incorporated places hold 3.7% of those residents; the other 96.3% live outside any of them. Testing is reported here more often than across the state: CDC's 2,451 reported tests for 2008 to 2017 come to 24.5 for every 1,000 residents (2025 estimate), against 6.0 for Virginia.

From Stephens City to Middletown, CDC publishes no figure by town: each reads Frederick County's.

The cities and towns in Frederick County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Stephens City2,207+8.6%2.2%
Middletown1,471+8.2%1.5%

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).

Frederick County, Homes

Homes in Frederick County

Frederick County is a place of houses on their own lots: 76% of its 36,617 homes are detached single-family houses, against 61% across Virginia. Much of Frederick County is recent building: 40% of its homes have gone up since 2000 and the middle year built is 1994, 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 in Frederick County, Virginia, 2019 to 2023
HomesFrederick CountyVirginia
Housing units36,6173,654,784
Detached houses76%61%
In buildings of 5 or more8%19%
Mobile homes6%4%
Built before 19609%19%
Built since 200040%25%
Middle year built19941984
Owner-occupied78%67%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.