To determine if your combo alarm has reached its end-of-life:
If the alarm emits a chirp every 30 seconds, it is either an end-of-life alert or a sensor error.
If the alarm emits a chirp every 60 seconds, it indicates the battery power is not sufficient to power the unit in full alarm.
An end-of-life or sensor error will not respond to a battery change.
If your alarm has reached its end-of-life, this is how you can dispose of it.