Keep your family safe with this battery operated smoke and carbon monoxide alarm; battery powered alarms provide continuous monitoring of CO levels, even if there's a power failure Features an electrochemical Carbon Monoxide sensing technology as well as a photoelectric sensor that detects the larger particles of a smoldering fire Indicator lights on the face of the unit display the presence of smoke or carbon monoxide, while an 85dB siren provides a clear, loud warning upon detection Battery-operated unit installs quickly and easily without an electrician, To ensure all alarms will sound when threat is detected Simple to use, A single button tests the unit or silences the alarm. Low battery signal mute, quiets low battery signal for up to 8 hours