My smoke detectors have been chirping for a while. I checked the 9v battery with the multimeter to see if they died. Nope, still good I checked the detector’s sticker on the back and saw it was made in 2003. They’re 20 years old now and I guess no longer good. So, I ordered a new pack of hardwired interconnect detectors.
I just changed all mine, got some that come with a remote to silence them. They’ll all go off, you press the button once and they all turn off except for the one that triggered it. You press again to turn it off.