Locations and reports
Radon Levels in Washington
What this means for you
- Your area: EPA rates 7 of Washington's 39 classified counties Zone 1, the highest of its three radon zones. Zones are predictions for whole counties, and homes with elevated levels occur in all three zones.
- Local tests: CDC publishes Washington's radon test results by county. Open your county below to see its figures.
- Your home: The only way to know your home’s level is to test it.
pCi/L (picocuries per liter) is the unit radon is measured in. EPA recommends fixing a home at 4 pCi/L or above, its action level.
For Washington, EPA's Map of Radon Zones places 7 of its 39 classified counties in Zone 1, highest predicted potential, a prediction for each county as a whole. Radon levels vary from home to home, so only a test measures the level in yours.
Predicted: EPA radon zone
39 of 39 counties classified
EPA classifies counties, not states. Of the 39 counties in Washington with a zone, 7 are in Zone 1, 14 in Zone 2 and 18 in Zone 3.
- Zone 1: Highest predicted potentialgreater than 4 pCi/L7 of 39 counties · 17.9%
- Zone 2: Moderate predicted potential2 to 4 pCi/L14 of 39 counties · 35.9%
- Zone 3: Lower predicted potentialless than 2 pCi/L18 of 39 counties · 46.2%
An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.
This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
CDC publishes Washington's radon test figures by county: 39 of its 39 counties have one. Each county's share is in the county list.
Washington, In figures
Washington in figures
What the published data says about Washington, in words. A zone and a share of tests describe an area, never the level in any one home.
Predicted
PredictedEPA places 7 of Washington's 39 counties in Zone 1, 14 in Zone 2 and 18 in Zone 3.
Zone 1 counties, A to Z, begin with Clark County, Ferry County and Okanogan County; the county section below lists all 7.
Compared
Calculated by Radon41118% of Washington's counties with a zone on file are in Zone 1, a smaller share than across all U.S. counties (34%). It is a share of counties, not of land, people or homes.
Reported tests
MeasuredCDC has no statewide testing figure for Washington on file here.
39 of the 39 counties have a published county figure; the most tests in each one's latest year were reported for Spokane County (557 in 2020), Clark County (355 in 2020) and King County (336 in 2020).
Washington's radon program is the Radon Program, run by Washington State Department of Health; its contacts are under Local resources.
Washington, Counties
Washington counties by EPA zone
PredictedAll 39 counties, by the zone EPA predicts for each. Every county has its own report.
Zone 1: highest predicted potential7
- Clark County17.6% of reported tests at or above 4 pCi/L, 2020
- Ferry County20.0% of reported tests at or above 4 pCi/L, 2020
- Okanogan County60.7% of reported tests at or above 4 pCi/L, 2020
- Pend Oreille County20.0% of reported tests at or above 4 pCi/L, 2020
- Skamania County52.9% of reported tests at or above 4 pCi/L, 2020
- Spokane County40.6% of reported tests at or above 4 pCi/L, 2020
- Stevens County37.8% of reported tests at or above 4 pCi/L, 2020
Zone 2: moderate predicted potential14
- Adams County50.0% of reported tests at or above 4 pCi/L, 2020
- Asotin County0.0% of reported tests at or above 4 pCi/L, 2020
- Benton County4.8% of reported tests at or above 4 pCi/L, 2020
- Columbia County0.0% of reported tests at or above 4 pCi/L, 2019
- Douglas County25.0% of reported tests at or above 4 pCi/L, 2020
- Franklin County25.0% of reported tests at or above 4 pCi/L, 2020
- Garfield County100.0% of reported tests at or above 4 pCi/L, 2019
- Grant County50.0% of reported tests at or above 4 pCi/L, 2020
- Kittitas County20.0% of reported tests at or above 4 pCi/L, 2020
- Klickitat County30.0% of reported tests at or above 4 pCi/L, 2020
- Lincoln County45.5% of reported tests at or above 4 pCi/L, 2020
- Walla Walla County20.6% of reported tests at or above 4 pCi/L, 2020
- Whitman County29.4% of reported tests at or above 4 pCi/L, 2020
- Yakima County5.3% of reported tests at or above 4 pCi/L, 2020
Zone 3: lower predicted potential18
- Chelan County15.0% of reported tests at or above 4 pCi/L, 2020
- Clallam County8.3% of reported tests at or above 4 pCi/L, 2020
- Cowlitz County4.2% of reported tests at or above 4 pCi/L, 2020
- Grays Harbor County0.0% of reported tests at or above 4 pCi/L, 2020
- Island0.0% of reported tests at or above 4 pCi/L, 2020
- Jefferson County14.3% of reported tests at or above 4 pCi/L, 2020
- King County5.0% of reported tests at or above 4 pCi/L, 2020
- Kitsap County0.0% of reported tests at or above 4 pCi/L, 2020
- Lewis County70.0% of reported tests at or above 4 pCi/L, 2020
- Mason County0.0% of reported tests at or above 4 pCi/L, 2020
- Pacific County0.0% of reported tests at or above 4 pCi/L, 2020
- Pierce County4.3% of reported tests at or above 4 pCi/L, 2020
- San Juan County25.0% of reported tests at or above 4 pCi/L, 2020
- Skagit County4.8% of reported tests at or above 4 pCi/L, 2020
- Snohomish County1.0% of reported tests at or above 4 pCi/L, 2020
- Thurston County6.5% of reported tests at or above 4 pCi/L, 2020
- Wahkiakum County0.0% of reported tests at or above 4 pCi/L, 2020
- Whatcom County20.0% of reported tests at or above 4 pCi/L, 2020
Washington, Local resources
Local resources in Washington
Who to ask in Washington: the state's radon program, test kits and professionals.
Radon Program
Washington State Department of Health
Washington’s radon program answers questions about testing, mitigation and the rules where you live.
- Phone
- 360-236-3200
- doh.radon@doh.wa.gov
Test kits
The program says: We have a limited supply of free radon test kits.
Radon professionals
No professionals are listed in Washington yet. The state program can point you to registered testers and mitigators.
See the Washington directoryWashington, Questions
Questions about radon in Washington
Common questions9 questions, answered from the figures above
Is radon a problem in Washington?
EPA's Map of Radon Zones places 7 of the 39 Washington counties it classifies in Zone 1, the highest predicted potential, 14 in Zone 2 and 18 in Zone 3. An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.
Who does radon mitigation in Washington?
Radon411 has no certified mitigators listed for Washington yet. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional.
How radon mitigation worksWhat mitigation costsRadon professionals in Washington
Which Washington counties are in EPA radon Zone 1?
7 counties are in Zone 1: Clark County, Ferry County, Okanogan County, Pend Oreille County, Skamania County, Spokane County, Stevens County. Zone 1 is EPA's class for highest predicted potential, a predicted average indoor screening level greater than 4 pCi/L. A zone is a prediction for a county, not a measurement of any home.
Radon in Clark CountyRadon in Ferry CountyRadon in Okanogan County
How do I get a radon test in Washington?
EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. The Washington radon program is the place to ask about certified testers and any test kit offer it runs.
How to test a homeFree and low-cost kits by stateWashington radon program
Which Washington counties have the highest radon?
39 of Washington's 39 counties have an EPA radon zone published here. Radon411 will not rank counties on data it does not hold, and a zone is a prediction for an area rather than a measurement of any building.
What share of radon tests in Washington are high?
CDC has published no statewide radon testing statistics for Washington, so we cannot give a figure. Where CDC does publish one, the percentage describes radon tests reported to CDC, not homes.
Which EPA region is Washington in?
Washington is in EPA Region 10: Pacific Northwest.
Do I need to test my home in Washington?
Yes, wherever you live in the state. Testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L.
Why does this page show coverage rather than one radon level for Washington?
A statewide figure averages counties with very different geology and very different numbers of reported tests, so it hides more than it shows. The county report is the level at which the EPA zone, the geologic potential and the reported testing statistics are actually published, which is why the county table above links to every one of them.
What these figures mean if you own, buy, sell or rent
The zone counts on this page describe counties across Washington. They are predictions for areas, and none of them measures your building.
- How to test a home
If you own your home
Test the lowest lived-in level; a short-term kit screens in days, a long-term kit reflects the year.
- Buying a house: radon guide
If you are buying
Ask for past results and any system's post-mitigation test, and test during the sale.
- Selling a house: radon guide
If you are selling
Testing before you list puts the timing in your hands; disclosure rules differ by state.
- Radon in rental homes
If you rent, or rent out a home
A tenant can test; a fix is the owner's to make, and duties differ by state.
How long a test has to run, under what conditions, and what EPA says a result means: the testing standard, in full.
Washington, Products
Testing and mitigation products
Whatever the figures for Washington show, only a test tells you about one home.
Testing
- Short-term test kitsPassive detectors exposed for a few days under closed-building conditions, then analyzed by a lab.
- Long-term test kitsDetectors exposed for more than 90 days, for a closer picture of the annual average.
- Continuous monitorsPowered devices that log radon on a repeating cycle, often used for transaction tests.
- Digital detectorsConsumer devices that display a running radon reading without a lab.
- Water radon testsKits for radon dissolved in well water, analyzed by a lab.
Mitigation
- Mitigation fansThe inline fan that keeps a soil depressurization system running, sized by the installer.
- System indicatorsU-tube manometers and fan alarms that show whether a mitigation system is still working.
- Sealing materialsCrack, joint and sump sealing used alongside a mitigation system, not instead of one.
Washington / Next steps
What to do next
Learn
Know what radon is
What radon is, how it gets indoors, and why a county zone is not a reading for your home.
Learn about radonTest
Test the building you live in
Short-term or long-term, where the device goes, and closed-house conditions.
How to testFix
Bring a high level down
How a mitigation system works, and the retest that confirms it.
How mitigation worksFind a pro
Hire a certified professional
Measurement and mitigation professionals by state, with their certifications.
Find a professional
Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.