Smoke & Carbon Monoxide Alarm alerts you to both smoke and carbon monoxide (CO) using a single unit. Cutting-edge technology sends fast alerts that give your family more time to get out safely and enhanced sensing technology reduces false alarms often caused by cooking. It runs on two AA replaceable batteries (included) for continual detection even during outages and alerts you to both smoke (photoelectric sensor) and carbon monoxide (electrochemical). Self-testing alarm is easy to install with the included twist-and-click mounting bracket. Equipped with end-of-life notifications, the flashing red alarm will beep to remind you it's time to replace it 10 years after it is powered. Different alarms indicate the issue so you can react appropriately: three long beeps for fire, four quick beeps for carbon monoxide and one chirp for low battery. Alarm memory alerts your if smoke or CO has been detected in the last 24 hours.