Smoke detectors and their batteries are the most inexpensive protection available. And complete families have been lost because a family member was irritated at the chirping sound that indicates the need for a new battery. Every smoke detector has a test button that checks the electrical circuits and smoke sensor when it is pressed. Pressing the test button also causes the detector to sound its alarm to tell you that everything is working. When the battery needs to be replaced, most detectors sound a chirping alarm.
Some detectors have a flag that pops out when the battery is discharged.
Maher advises testing smoke detectors at least once a month, especially during the heating season. Frequent checking will not significantly weaken the battery. Your life and others may depend on that battery in the next 24 hours. Some smoke detectors are powered by the home's electricity and don't have batteries. These hard-wired detectors should also be tested frequently.