Washington State Department of Health
Washington radon (air)
No state license roster to republish. Updated / retrieved 2026-10-01 (US/Pacific).
If you are not sure you need a pro yet, see when a DIY radon test kit is enough or how to test a home for radon.
Washington DOH does not publish a public statewide list of radon measurement or mitigation businesses and does not offer a state radon license roster on its site. This page does not invent company names, phones, licenses, or addresses to fill that gap.
DOH’s “Hiring a Certified Radon Professional” section points homeowners to nationally certified providers instead: search through NRPP or NRSB Find a Professional (the same links DOH publishes). Filter by measurement vs. mitigation, then re-check the credential before hiring. For general contracting work, DOH also links Washington Labor & Industries — Hiring a Contractor.
What DOH says homeowners can do
- Radon is a naturally occurring radioactive gas from rocks and soils. You cannot see, smell, or taste it — testing indoor air is the only way to know a building’s level.
- EPA’s recommended action level remains 4.0 pCi/L (about 10 times typical outdoor air). DOH notes that other countries recommend action closer to 2.7 pCi/L; the goal is to reduce indoor radon as much as reasonably possible.
- Test where people spend time (living areas and bedrooms), not unused broom closets or crawl spaces. Short-term kits (about 3–4 days with closed-house conditions), long-term tests, or continuous monitors can all measure radon; interpret results with the testing conditions in mind.
- DOH has offered a limited supply of free radon test kits for Washington homes. Request through the DOH form: doh.wa.gov/form/radon-test-kit-access-form (DOH asks you to request a kit only if you will use it; allow time for delivery).
- If a test shows elevated levels, DOH describes simple DIY steps (increase outdoor air exchange when appropriate, seal foundation cracks, maintain crawl-space vapor barriers and foundation vents) and then retest. If levels stay high, hire a certified radon professional via NRPP or NRSB.
- Radon maps and past test data are available through the Washington Tracking Network (WTN) for context only — they are not a substitute for testing your own home.
- Questions: Washington State Indoor Radon Program — doh.radon@doh.wa.gov or 360-236-3200.
Official sources
- Washington DOH — Radon (retrieved 2026-10-01; primary hub)
- Washington DOH — Radon test kit access form (retrieved 2026-10-01; free kit request while available)
- Washington Tracking Network — Radon data and maps (retrieved 2026-10-01)
- NRPP Find a Pro (linked from DOH for certified professionals)
- NRSB Find a Professional (linked from DOH for certified professionals)
- Washington L&I — Hiring a Contractor (linked from DOH)
- U.S. EPA Radon (linked from DOH)
This index does not rank contractors or take referral fees. No Amazon kit links on this state page. This page covers indoor air only, not well water.