The Kidde KN-COSM-BA battery-operated carbon monoxide and smoke alarm combines two important safety devices into a single unit. This alarm includes a voice warning system that makes four announcements: fire, carbon monoxide, low battery, or smart hush activation. The voice alarm eliminates any confusion and clearly warns you and your family of a smoke or carbon monoxide danger, or if your battery is in need of replacement. This unit uses three AA batteries, protecting you and your family even during a power outage. This alarm uses ionization-sensing technology for the smoke alarm. Ionization-sensing alarms may detect invisible fire particles (associated with flaming fires) sooner than photoelectric alarms. Photoelectric-sensing alarms may detect visible particles (associated with smoldering fires) sooner than ionization alarms. Kidde strongly recommends that both ionization and photoelectric smoke alarms be installed to help ensure maximum detection of the various types of fire that can occur within the home. KN-COSM-BA Battery-Operated Combination Smoke and CO Alarm at a Glance Employs both smoke and carbon monoxide sensors Stand-alone battery-operated alarm is easy to install throughout the home, as no wiring is needed Features a hush button to silence the alarm for non-emergency situations like a smoky dinner Voice alarm eliminates confusion and clearly warns of smoke/CO danger or low battery Protects from two different hazards, smoke and carbon monoxide, and has a different voice warning for each hazard. The battery-operated KN-COSM-BA offers easy installation. Combination Smoke/Carbon Monoxide Alarm The Kidde combination carbon monoxide and smoke alarm includes a voice warning system that eliminates confusion and clearly warns you and your family of a smoke or carbon monoxide (CO) danger, of low battery, or of hush-mode setting.