The First Alert SCO501CN-3ST Combination Smoke and Carbon Monoxide Alarm with Voice Location detects both smoke and carbon monoxide in a single device. Designed for those who want a comprehensive detection system without hiring an electrician, this battery-operated smoke and carbon monoxide detector is an ideal solution. This technology interconnects the detector with other compatible First Alert wireless-enabled alarms in your home to create a wireless safety network. This allows them to communicate with each other and alert you when there is a problem across the house, in a different room, or on a different floor. The photoelectric smoke sensor is designed to reduce false alarms from cooking smoke or shower steam while remaining sensitive to real danger. The advanced electrochemical CO sensor detects carbon monoxide leaks from multiple sources, including faulty fuel-burning appliances. A loud 85-decibel siren and a voice alarm indicate where and what the threat is.