Radon Levels in Washington
Washington is classified as an EPA Zone 2 state with a moderate risk for radon. Average indoor radon levels range from 1 to 4 pCi/L, and approximately 11% of Washington homes test above the EPA action level of 4.0 pCi/L.
Washington Radon Summary
Key Facts About Radon in Washington
- Eastern Washington has higher radon levels than western Washington
- The Spokane area has particularly elevated levels due to granite geology
- Western Washington's wet climate and geography limit radon migration
- WA DOH provides radon resources
Washington Testing Requirements & Recommendations
Washington recommends testing all homes, particularly in eastern Washington.
Spokane-area contractors are experienced with the unique geology of eastern Washington.
Major Cities in Washington
Radon levels can vary significantly within Washington depending on local geology. All residents — regardless of city — should test their specific home, as neighborhood-level radon varies independently of broader state and county averages.
What Should Washington Residents Do?
Test Your Home
Use a short-term charcoal test kit ($15–$25) for an initial reading, or a continuous radon detector for ongoing monitoring. Test in your basement or lowest livable area.
Understand Your Result
If your result is below 2.0 pCi/L: monitor periodically. Between 2.0–4.0 pCi/L: consider mitigation. Above 4.0 pCi/L: the EPA recommends mitigation. Above 8.0 pCi/L: take action promptly.
Hire a Certified Contractor if Needed
Look for NRPP or NRSB-certified radon mitigation contractors in Washington. Mitigation systems typically cost $800–$2,500 and can reduce radon levels by 50–99%.
Verify with a Follow-Up Test
After mitigation, test again to confirm the system is working. Retest every 2 years, or after significant home renovations.
Some links are affiliate links. Learn more.
