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Radon Levels in Ferry County, Washington

EPA puts Ferry County in Zone 1, its highest radon zone, and only 10 radon tests from it are on file with CDC (2020). 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

  • Highest bordering

    36.2%

    Stevens County

    Stevens
    36.2%
    Okanogan
    35.0%

    2 of 3 neighbours have 30+ tests, 2008 to 2017

  • Nearest county

    36.2%

    Stevens County, 31 miles

    Stevens
    36.2%
    Washington
    25.5%

    Share at 4+ pCi/L, 196 tests, 2008 to 2017

  • Ground above low

    100.0%

    47.3 pts above Washington

    Ferry
    100.0%
    Washington
    52.7%

    Share of land USGS rates moderate or high potential

  • Tests reported

    28

    Too few for a share

    Ferry
    28
    Needed
    30

    2019

  • 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

Read a result for Ferry County

Starts at EPA's action level

4.0pCi/L

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

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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.

Interpret this readingWhat a fix costs

The data

Ferry County, At a glance

Ferry County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Ferry 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 Ferry County, 2020

Share of reported tests at or above 4 pCi/L, by year, Ferry County
Share of reported tests at or above 4 pCi/L, by year, Ferry County
YearShare of reported tests at or above 4 pCi/L
201418.8%
201516.7%
201621.4%
201755.0%
201836.4%
201917.9%
202020.0%

2020: 20.0%. Across these years the share ran from 16.7% to 55.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 10 tests were reported to CDC for Ferry County over 2020, 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: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).

How to read these figures

Ferry County, Compared

Ferry County radon figures, compared

Calculated by Radon411

CDC's largest figure for Ferry County rests on 28 tests in 2019, 5 of them at or above 4 pCi/L, so each test moves its share by 3.6 points and no rank or comparison is drawn from it. Results reached as high as 13.4 pCi/L, with a middle value of 0.3 pCi/L.

Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Stevens County reported the largest share at or above 4 pCi/L, 36.2%, and Okanogan County the smallest, 35.0%. Farther out, Pend Oreille County (57 miles away) at 63.2%, Spokane County (78 miles away) at 41.4% and Chelan County (106 miles away) at 14.6% have figures too. Pooled across 39 Washington counties, 25.5% of reported tests reached that level; across every county in the country with a figure, 35.7%.

Statewide for the same period, Pend Oreille County reported the highest share (63.2%) and Snohomish County the lowest (2.3%). EPA's 1993 map puts Ferry County in Zone 1, the map's highest label: a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.

Washington, the United States and the counties around Ferry County, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedian
Washington, pooled39 counties, pooled8,20125.5%Not pooled
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled
Pend Oreille Countyhighest in the state3863.2%4.8 pCi/L
Snohomish Countylowest in the state2652.3%0.5 pCi/L
Lincoln County, WAborders it1540.0%3.1 pCi/L
Stevens County, WAborders it19636.2%2.3 pCi/L
Okanogan County, WAborders it4035.0%2.3 pCi/L
The nearest Washington counties to Ferry County with 30 or more tests, 2008 to 2017, laboratory
CountyDistanceTestsAt or above 4 pCi/LMedian
Stevens County31 mi19636.2%2.3 pCi/L
Okanogan County56 mi4035.0%2.3 pCi/L
Pend Oreille County57 mi3863.2%4.8 pCi/L
Spokane County78 mi3,12541.4%2.9 pCi/L
Chelan County106 mi4814.6%1.8 pCi/L
Whitman County118 mi5822.4%1.5 pCi/L
Skagit County148 mi362.8%0.8 pCi/L
Whatcom County149 mi1115.4%0.9 pCi/L
Ferry County radon tests by year, against Washington's pooled share
YearTestsAt or above 4 pCi/LMedianHighestWashington, pooledChange from the row before
20201020.0%1.6 pCi/L8.3 pCi/L19.0%+2.1 points
20192817.9%0.3 pCi/L13.4 pCi/L20.9%−18.5 points
20181136.4%1.8 pCi/L6.8 pCi/L16.1%−18.6 points
20172055.0%4.4 pCi/L16.8 pCi/L19.1%+33.6 points
20161421.4%1.9 pCi/L20.0 pCi/L16.6%+4.7 points
20151216.7%1.6 pCi/L13.5 pCi/L17.4%−2.1 points
20141618.8%2.4 pCi/L17.0 pCi/L15.0%First on file

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

Ferry County, Geology

The ground under Ferry County

Predicted

Most of the ground under Ferry County is one class on USGS's geologic map: 99.6% of its land is high radon potential, with 0.4% moderate. All of it lies in the area the map calls Okanogan Highland, to which USGS gives a radon index of 16, in the high band (12 to 17).

USGS's geologic areas under Ferry County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Okanogan HighlandGlaciofluvial outwash and granitic material. Outwash is generally uranium-bearing.High1699.6%

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

Ferry County beside the ground around it

Ferry County has more high-potential ground than Washington as a whole: 99.6% of its land against 13.7%. Of the 3 counties that border it, 1 has more high-potential ground, Stevens County the most at 99.8%.

Share of land by USGS radon potential: Ferry County, the 3 counties bordering it and Washington
AreaEPA zoneLow potentialModerate potentialHigh potential
Ferry CountyZone 1None0.4%99.6%
Stevens CountyZone 1None0.2%99.8%
Okanogan CountyZone 161.3%None38.7%
Lincoln CountyZone 2None95.3%4.7%
Washington38 counties, pooled by land areaVaries46.4%39.0%13.7%

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

Local help

Ferry County, Local resources

Radon testing and mitigation in Ferry County

What Washington's program says
Phone
360-236-3200
Email
doh.radon@doh.wa.gov

What it means

Ferry County, Questions

Questions about radon in Ferry County

Are radon levels high in Ferry County?

In 2020, 20.0% of the radon tests reported to CDC for Ferry County, Washington were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.6 pCi/L. Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Stevens County reported the largest share at or above 4 pCi/L, 36.2%, and Okanogan County the smallest, 35.0%.

Which counties border Ferry County?

Ferry County borders 3 counties: Stevens County, Okanogan County and Lincoln County.

Products

Ferry County, Products

Testing a home in Ferry County

No CDC figure names Ferry County; the nearest county with one, Stevens County (31 miles away), reported 36.2% 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. In Zone 1 the year-round level in Ferry 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

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

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Ferry County, Bordering counties

Counties bordering Ferry County

Calculated by Radon411

Ferry County, Cities and towns

Cities and towns in Ferry County

The Census Bureau estimates 7,517 residents in Ferry County for July 1, 2025, 318 more than in 2020 (+4.4%). Spread over its land, that is 3.4 people to the square mile. Republic, its one incorporated place, has 1,016 residents, 13.5% of the total. Testing is reported here more often than across the state: CDC's 28 reported tests for 2019 come to 3.7 for every 1,000 residents (2025 estimate), against 0.5 for Washington.

Republic is the one incorporated place here; CDC publishes no figure by town, so it reads Ferry County's.

Republic, Ferry County: residents on July 1, 2025
PlaceResidentsSince 2020Share of residents
Republic1,016+3.4%13.5%

One incorporated place, 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).

Ferry County, Homes

Homes in Ferry County

Of Ferry County's 4,105 homes, 74% are detached houses, against 62% across Washington; 22% are mobile homes. Half of its homes were built before 1986, close to Washington's 1984: 15% date from before 1960 and 27% from 2000 or later. Owners live in 76% of the occupied homes (Washington: 64%), so for most households a test and a fix are their own to order.

Homes in Ferry County, Washington, 2019 to 2023
HomesFerry CountyWashington
Housing units4,1053,262,667
Detached houses74%62%
In buildings of 5 or more3%22%
Mobile homes22%6%
Built before 196015%21%
Built since 200027%28%
Middle year built19861984
Owner-occupied76%64%

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