That CO alarm is giving me a headache

OK, yes that is an old joke, but I do have a slight mystery over the CO alarm. This first happened last year, and drove me round the bend. A chirp every 49 seconds. This is normally a smoke alarm with low battery. The problem is that we have 8 alarms in the house, and trying to work out which is chirping is not as easy as it sounds, especially when it is 2am, as it always is with these tings. I…