On Fri, 11 Nov 2011 17:03:23 +0000, Frederick Williams wrote:

Since these things contain radio isotopes, may they be thrown in the
dustbin, or does one need to take special care when disposing of them?

They contain a tiny (0.3 micro grams) amount of Americium 241
principally an alpha emitter. Alpha particles are big (a Helium-4
nucleus) and don't travel very far, even in air, before being
absorbed. A sheet of paper will stop them.

Having said that you don't want to ingest an alpha emitter and have
it lodge somewhere. It will damage tissue, in it's immediate
vicinity, over a period of time.

I've not heard of special collection or disposal facilities for smoke
detectors in the UK. But then I haven't been looking.

--
Cheers
Dave.