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 bought the optical ones, and got so many false alarms. SO MANY. I had to remove them and get the old kind.
The old americium’s went off randomly at night and at the mention of bacon… at the grocery store… The new optical ones we have are sensitive to heated aerosols like hairsprays plus hair dryers.