Smoke detectors typically fall within two categories: photoelectric and ionization. When it comes to disposal, old photoelectric detectors can be safely put in the trash, so long as you remove the battery first. Read on for information about ionization detectors.
Ionization-Based Smoke Detectors:
Ionization detectors contain a small amount of Americium 241, a radioactive isotope. When in use, these detectors are perfectly safe, as the radioactive material is shielded by a metal chamber inside the device. If dismantled, however, the radioactive material can become exposed. For this reason, you should never try to take apart an old ionization detector.
So how do I dispose of an ionization detector?
Some local hazardous waste collection centers will accept ionization smoke detectors.
You can also try to send your old detector back to the original manufacturer. Locate the brand name and/or address on the back of the device, or find the information in the user’s manual. After removing the battery, send the whole unit back intact (do not try to disassemble) with a note indicating that the device is intended for disposal.
For more information call 1-800-963-4776 or check out the website http://www.lessismore.org/materials/99-smoke-detectors