The First Alert(R) 120 V hardwired smoke alarm utilizes both photoelectric and ionization sensors which allows for optimal detection. For additional safety, it also comports a battery backup to ensure the operation in case of power failure. The alarm reliably detects fast flaming fires and smouldering fires. The alarm features an alarm latch that easily identifies initiation alarm even after the condition has subsided as well as a low battery latch that indicates which unit is in low battery condition. It is equipped with a low battery chirp silence for up to eight hours or silence nuisance alarm. This product is backed by a 10-year limited warranty.