120V AC Wire-in Smoke Alarm with 9V Battery Backup This smoke alarm uses ionization sensing technology. Ionization sensing alarms may detect invisible fire particles (associated with fast flaming fires) sooner than photoelectric alarms. Photoelectric sensing alarms may detect visible fire particles (associated with slow smouldering fires) sooner than ionization alarms. Leading authorities recommend that both ionization and photoelectric smoke alarms be installed to help ensure maximum detection of the various types of fires that can occur within the home.  Ionization Technology – May detect invisible fire particles (associated with flaming fires) sooner than photoelectric alarms. 120 V Interconnectable – Will interconnect with up to 24 other devices (18 of which can be initiating). 9 V Battery Backup (included) – Provides continuous protection even during power outages. Multi-function One Button Design includes: Hush® Feature – Temporarily silences nuisance alarms. Test Feature – Simultaneously tests the unit’s electronics and verifies alarm operation. Tamper Resist Feature – Tamper resist locking pin deters from tampering or theft. Item #: P1275CA We suggest to use them everywhere except close the strove. which suggest a photoelectric alarms. Especially if you are cooking a lot. Technical Specifications Model: i12040CA (i12040ACA) Power Source: 120 V AC, 60 Hz, 80 mA max per alarm, 9 V battery backup Sensor: Ionization Audio Alarm: 85dB at 10ft Temperature Range: 4.4˚C (40˚F) to 37.8˚C (100˚F) Humidity Range: 10%-95% relative humidity, non-condensing Size: 12.7 cm in diameter x 3.6 cm depth Weight: 0.2 kg Interconnects: Up to 24 Kidde devices Warranty: 10 year limited