[Rick Lee]

I'm pretty religious about this subject, since my house and life were saved by one about five yrs. ago. I woke up this morning to a chirping smoke alarm in about 1-2 min. intervals. I assumed this was a dying battery and it's time to change them all. I have the Firex brand, which plugs into the house wiring and also has a 9 volt battery. I assume the battery is a backup to house power. So how the hell is thing still chirping when I have it unplugged and the battery removed? Do these things have internal batteries that store auxiliary power? This alarm is dated Aug. 2000. Time to upgrade or just swap out batteries?