The First Alert BRK PRC700VA Talking Smoke and Carbon Monoxide Alarm features a photoelectric smoke sensor and an electrochemical carbon monoxide sensor. The photoelectric sensor detects larger smoke particles from smoldering fires from objects like cigarettes burning on furniture or in trash cans. A patented smoke entry system further enhances the detector's reliability by providing a direct path to the smoke sensor. This voice alarm not only alerts you whether the threat is smoke or carbon monoxide, but also uses 11 pre-programmed locations to tell you the location of the danger in your home. The battery-operated smoke and CO detector can be installed easily, with no wires or electrician required, and its slim profile will seamlessly blend in with your home decor. The alarm operates on two AA batteries. Battery operation means that even in the event of a power outage, the alarm can still function.