Why is my smoke alarm sounding when I install a battery or turn on the power?

Question

How come my smoke alarm sounds when I install a battery or turn on the AC power?

Answer

It is sometimes normal for smoke alarms to sound briefly (up to 5-10 seconds) when they are powered-up, depending on the manufacturer and model. If the alarm continues to sound and no smoke is present, the cause may be:

  • Insufficient battery or AC power.
    Very low batteries or insufficient electrical power (brown-out) may cause a continuous weak sounding alarm. For battery models, change the battery. For 240v models, temporarily disconnect power at the service panel until the brown-out is over.

  • Incompatible warning device.
    If an incompatible alarm or auxiliary device is linked into a series of 240v smoke alarms it may cause the system to alarm.