What is one of the most common signs that a smoke detector needs its battery replaced?

A chirping sound at regular intervals is a widely recognized indication that a smoke detector's battery is low and needs to be replaced. This chirping serves as an alert for users to take action, ensuring that the smoke detector is fully operational to provide adequate safety measures.

In contrast, a continuously sounding alarm typically indicates the presence of smoke, suggesting that the detector is functioning correctly to detect potential fires rather than signaling a battery issue. A red indicator light that remains off may imply the unit is powered off or not functioning but does not specifically indicate a need to change the battery. Additionally, a vibrating detector would be highly unusual, as smoke detectors do not typically vibrate as a signal for maintenance or malfunction. Therefore, the chirping sound is the most reliable and common sign that maintenance is needed regarding the battery.