Stupid smoke alarm is beeping downstairs which means battery needs replacing. It’s on the mains. I went down 1.5 hours ago to shut front room door went back up. Can’t go back to sleep! I’m exhaustrd! Da has sleep walked into my bed so he’s snoring and can hear the beeping. I don’t think I have the battery for the alarm so can’t eveb watch tv as it’s in the same room! Do all smoke alarms use a square battery? I’m worried if I open it up to look that I’ll somehow set the alarm off and wake the dc!