EPA radon zones
Washington radon map: every county's zone
7 of Washington's 39 counties are EPA radon zone 1 (predicted average above 4 pCi/L), 14 are zone 2 and 18 are zone 3. High readings occur in every zone, so EPA recommends testing every home.
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
How much does radon mitigation cost?
Most single-family systems cost $800 to $2,500 installed, depending on foundation type and how many suction points are needed. A follow-up test confirms the system works.
What do the zones mean?
EPA radon zones describe counties, not houses. Zone 1 counties have a predicted average indoor level above 4 picocuries per liter (pCi/L), Zone 2 between 2 and 4, Zone 3 below 2. Homes with high levels are found in every zone, which is why EPA recommends that every home be tested, and fixed at 4 pCi/L or above.
Washington cities: water and radon
Source: EPA Map of Radon Zones.