The First Alert SCO7CN Battery-Operated Combination Smoke and Carbon Monoxide Alarm with Voice and Location delivers both smoke and carbon monoxide detection in a single unit. Equipped with a photoelectric sensor, the alarm detects smoke produced by smoldering fires while keeping false alarms to a minimum. The unit also features an advanced electrochemical CO sensor that detects carbon monoxide leaks from multiple sources such as faulty fuel-burning appliances and blocked chimneys. If a threat is detected, the unit alerts you using both visible and audible signals, including a loud 85-decibel siren and a programmable voice alarm that indicates the nature and location of the threat. This talking carbon monoxide and smoke detector is battery operated, so you can easily install it without the aid of an electrician. The alarm is powered by two AA batteries and features an easy-to-access battery compartment for quick replacements. And thanks to a convenient test/silence button, you can easily check whether your alarm is functioning properly and mute false alarms.