This isn't a funny :)
While I have been on HUKD this morning, my carbon monoxide detector was bleeping (and annoying me). It is one of those that says, "Battery cannot be replaced. Dispose of safely. This cover cannot be replaced once removed." Guess what? Removed cover and found three Eveready standard AAA batteries, put new ones in, replaced cover, and it works perfectly. Don't you hate lying companies?
Just in case you have one, at least give it a go. Mine would have gone to the recycling dump if I had not.