Radon by ZIP

Radon zones in Washington

Last updated

EPA’s Map of Radon Zones places 39 Washington counties in its three radon potential zones: 7 in Zone 1 (highest), 14 in Zone 2 (moderate), and 18 in Zone 3 (low).

7Zone 1 · Highest potential
14Zone 2 · Moderate potential
18Zone 3 · Low potential

What this means for Washington homes

Most Washington counties fall in Zone 3. EPA predicts lower average indoor levels (below 2 pCi/L) across much of Washington. That does not mean your home is low: EPA notes that elevated levels are found in Zone 3 counties too.

EPA’s guidance is the same everywhere: test your home, fix it if the level is 4 pCi/L or higher, and consider fixing between 2 and 4 pCi/L. The zone map is from 1993 and should not be used to decide whether a single home needs testing.

Washington radon program

EPA lists the following state contact for Washington: WA State Department of Health, Community and Environment: Radon, phone 360-236-3200. Website: doh.wa.gov/community-and-environment/contaminants/radon. State programs can tell you about local testing data, free or discounted test kits, disclosure rules for home sales, and credentialed radon professionals.

Washington counties and their EPA radon zones

CountyEPA radon zone
Adams CountyZone 2
Asotin CountyZone 2
Benton CountyZone 2
Chelan CountyZone 3
Clallam CountyZone 3
Clark CountyZone 1
Columbia CountyZone 2
Cowlitz CountyZone 3
Douglas CountyZone 2
Ferry CountyZone 1
Franklin CountyZone 2
Garfield CountyZone 2
Grant CountyZone 2
Grays Harbor CountyZone 3
Island CountyZone 3
Jefferson CountyZone 3
King CountyZone 3
Kitsap CountyZone 3
Kittitas CountyZone 2
Klickitat CountyZone 2
Lewis CountyZone 3
Lincoln CountyZone 2
Mason CountyZone 3
Okanogan CountyZone 1
Pacific CountyZone 3
Pend Oreille CountyZone 1
Pierce CountyZone 3
San Juan CountyZone 3
Skagit CountyZone 3
Skamania CountyZone 1
Snohomish CountyZone 3
Spokane CountyZone 1
Stevens CountyZone 1
Thurston CountyZone 3
Wahkiakum CountyZone 3
Walla Walla CountyZone 2
Whatcom CountyZone 3
Whitman CountyZone 2
Yakima CountyZone 2

County names follow the 2020 Census. Zones from the EPA Map of Radon Zones (text version). Rows marked “zone of” use the zone EPA gave the predecessor or surrounding county.

Next steps: read how to test your home, check a result with the level calculator, or look up a single address by ZIP code.

Sources

  1. U.S. EPA, EPA Map of Radon Zones (text version)
  2. U.S. EPA, EPA Map of Radon Zones and Supplemental Information (state radon contacts)
  3. U.S. EPA, EPA Maps of Radon Zones and Supporting Documents by State