The first Alert combination smoke and carbon monoxide alarm with voice location detects both smoke and carbon monoxide. It is a wireless enabled battery operated detector that features an 85 dB siren plus a voice alarm to let you know where the danger is. This technology allows other compatible First Alert wireless enabled alarms located in several areas of your home to communicate with each other, alerting you to a problem early even when it's on another floor. The smoke and carbon monoxide detector features a photoelectric smoke sensor and electrochemical carbon monoxide sensor.