Smoke & Carbon Monoxide Alarm alerts you to both smoke & carbon monoxide (CO) using a single unit. Cutting-edge technology sends fast alerts that give your family more time to get out safely. Enhanced sensing reduces false alarms often caused by cooking. It runs on two AA replaceable batteries (included) for continual detection even during outages & alerts you to both smoke (photoelectric sensor) & 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 & one chirp for low battery. Alarm memory alerts you if smoke or CO has been detected in the last 24 hours.