This smoke alarm functions as a stand alone unit or in an interconnected system. The Kidde PI2010 features Hush, allowing you to quickly silence nuisance alarms and also includes a tamper resist features that deters tampering and theft. 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.