... density in the air and provide an alarm.The detector is suitable for detect the smoke in house, shop ... library, computer house and storehouse etc.Stand alone Smoke Detector Main FeaturesHush functionAC power supply,9V back-up batteryTest ... low power indicationExecute criterion:EN14604;UL217Standalone Smoke Detector Technical Parameter Operating voltage,AC220V,with 9V back-up batteryTemperature Range, ...