The Kidde PI9000 dual sensor battery operated smoke alarm is powered by a 9V battery and provides continuous protection against smoke and fire hazards even during power outages. Operating in temperatures from 40 to 100 degrees Fahrenheit, the unit is tamper resistant and has a hush feature, allowing you to temporarily silence nuisance alarms. The dual ionization and photoelectric sensors offer the best protection against both fast, flaming fires which produce invisible fire particles and slow, smoldering fires which produce visible fire particles, protecting you and your family from any fire threat.