The Kidde Pi9000 is a 9V battery powered smoke alarm. This smoke alarm functions as a single unit smoke alarm and features Hush, allowing you to quickly silence nuisance alarms. The Pi9000 is easy to install, no wiring is required. This smoke alarm combines both photoelectric and ionization sensors. 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. The Kidde Pi9000, 9V battery powered smoke alarms provides continuous protection against smoke and fire hazards even during power outages. The Pi9000 also includes flashing LEDs to signal the alarm is functioning properly, a low battery warning and a loud 85dB alarm. The Kidde Pi9000 is UL listed and offers a 10-year limited warranty.