It is legal in Washington to dispose of smoke detectors in the garbage.
The City of Kirkland no longer accepts smoke detectors for recycling at City Hall.
King County Solid Waste Division states all smoke detectors can be disposed of in the garbage. Hazardous Waste facilities will not accept ionization smoke detectors.
What to do with smoke detectors
There are two common types of smoke detectors in homes: ionization and photoelectric detectors.
Ionization smoke detectors contain a very small amount of radioactive material known as Americium-241. Photoelectric-type smoke detectors do not contain any radioactive material. On your wall at home, ionization smoke detectors present no danger to your family as long as the smoke detector remains intact and undamaged. Never take apart an ionization smoke detector.
Once a smoke detector is to be replaced, remove the batteries for recycling and place the old smoke detector in the garbage.
You may also contact the smoke detector manufacturer to inquire about its disposal and recycling program to determine how to return the unit to the company. The U.S. Postal Service has created a contact chart for smoke detector manufacturers that can be found on their website for reference.