The Kidde 900-0102A Combination Carbon Monoxide & Smoke Alarm provides two important safety devices in a single unit. This alarm includes a voice warning system that announces “Fire, Carbon Monoxide, Low Battery and Smart HushTM 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 technologically advanced combination alarm is battery operated protecting you and your family even during a power outage when many incidences occur. This alarm uses ionization sensing technology. Leading authorities recommend that both ionization and photoelectric smoke alarms be installed to help insure maximum detection of the various types of fires that can occur within the home. Ionization sensing alarms may detect invisible fire particles (associated with fast flaming fires) sooner than photoelectric alarms. Photoelectric sensing alarms may detect visible fire particles (associated with slow smoldering fires) sooner than ionization alarms.