Firex/Kidde i5000 Hardwire Ionization Smoke Alarm with Battery Backup by Kidde Kidde model i5000 utilizes ionization sensing technology and ionization sensing alarms may detect invisible fire particles associated with flaming fires sooner than photoelectric alarms Alarm sounds at 85 decibels 9-Volt alkaline battery included (21025730) Hush button feature allows you to immediately silence the alarm When the alarm senses products of combustion and goes into alarm the red LED will flash one flash per second