Our carbon Monoxide detector kept going off for no reason, had it brought to the dealer TWICE and could find "nothing" wrong with it, except that it would go off in the middle of the night, every....damned ....time.
We disconnected it from the battery and then just plugged one in from home depot into the outlet.
As for the egg smell, we had the same thing, used the cleaner, and many other "home remedies" still an egg smell, then out of desperation we ended up pushing pure bleach through the system, let it sit for like half an hour, then ran water through it till clear....I know its not something you should do all the time, but we have only had to do it once so far in two years, and honestly, it was the only thing that worked.