The Kidde PI9010 is a 9 VDC 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 PI9010 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. Kidde strongly recommends that both ionization and photoelectric smoke alarms be installed to help insure maximum detection of the various types of fire that can occur within the home. The Kidde PI9010, 9 VDC battery powered smoke alarms provides continuous protection against smoke and fire hazards even during power outages. The PI9010 also includes flashing LEDs to signal the alarm is functioning properly, a low battery warning and a loud 85 dB alarm. The Kidde PI9010 is UL listed and offers a 10 years limited warranty.