The Kidde® KN-COSM-IB combination carbon monoxide and 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 or Hush™ Activation". The voice alarm eliminates any confusion and clearly warns of a smoke or carbon monoxide danger or if the battery is in need of replacement. This technically advanced combination alarm includes 9 V battery backup providing protection even during a power outage when many incidences occur. The KN-COSM-IB is an easy-to install alarm that is suitable for all living areas. It has a 7 years life and a 7 years limited warranty. This alarm uses ionization sensing technology. Ionization sensing alarms may detect visible fire particles (associated with flaming fires) sooner than photoelectric alarms. Photoelectric alarms may detect visible particles (associated with smoldering fires) sooner than ionization alarms. Leading authorities recommend that both ionization and photoelectric alarms be installed to help insure maximum detection of the various types of fires that can occur within the home.