"The alpha particles from the smoke detector do not themselves pose a health hazard, as they are absorbed in a few centimetres of air or by the structure of the detector.
The radiation dose to the occupants of a house from a domestic smoke detector is essentially zero, and in any case very much less than that from natural background radiation. The small amount of radioactive material that is used in these detectors is not a health hazard. On the other hand, the ability of domestic smoke detectors to save life and property has been demonstrated in many house fires.
Even swallowing the radioactive material from a smoke detector would not lead to significant internal absorption of Am-241, since the dioxide is insoluble. It will pass through the digestive tract, without delivering a significant radiation dose. (Americium-241 is however a potentially dangerous isotope if it is taken into the body in soluble form. It decays by both alpha activity and gamma emissions and it would concentrate in the skeleton.)
...Disposal of individual units can be in normal household garbage which goes to landfill."
~~~~~~~~~~~~~~~~~~~~
About thirty years ago I had a smoke detector that came with information that said something like, 'you could put a smoke detector against your skin for 10,000 years and not one isotope would enter your body.' So I haven't worried much about them since. But I have some old ones to dispose of and wanted to double-check the disposal rules, as I'd read you can just put them into the household trash.
I have two really old detectors I'll pitch, but several that are 11 years old. The recommendation is to replace detectors after ten years. Instead, I'll get all new ones, but keep the old ones for back up. For example, in the hallway I'll put one over each bedroom door, as well as a new detector in each bedroom. Yesterday, for the first time ever, I gently vacuumed the inside of the detectors, as per instructions.
