Smoke detectors typically fall within two categories: photoelectric and ionization. It is legal to dispose of photo electric smoke detectors in a trash cart because they are not considered hazardous waste. First, remove the batteries and recycle them properly. Find a battery drop-off location at call2recycle.org/locator.
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. To determine whether your detector is an ionization type, look on the back; it should either have the letter "I" or say ionization.
First Alert has a complimentary disposal program for up to 4 intact ionization smoke detectors (postage not included). These must be First Alert, BRK, Family Gard, or Onelink brand.
Curie includes a mail-in label with the purchase of a smoke detector.
Carbon monoxide detectors can be disposed in the trash cart, but first remove the batteries and recycle them properly.