reply to tommo
Re: smoke alarm Check the age - some have a "lifetime" counter in them, then chirp's at the end of their design life...
Failing that, try another battery (could be a dud).
Or, replace, they're cheap enough - a combo smoke/CO detector can be had for under $40, and a plain smoke is about $12 for the most basic of basic units. A combo ionizing/photo-electric would be my suggestion, assuming you have an existing CO detector.
I don't like the sealed ones with the 10 year battery, myself - I know the lithium batteries are supposed to last the life of the detector, but I prefer to put in fresh batteries twice a year. It's cheap insurance.