At a fraction of the size of a standard alarm it provides maximum protection with a new thinner, micro design, which adds an element of style to safety. It has an advanced smoke entry system with a photoelectric sensor that will detect regular and slow, smoldering fires and reduce false alarms that result from cooking and shower steam. Loud 85dB penetrating and powerful siren to ensure everyone is out of the building safely. Repeating horn pattern and an LED light flashes rapidly during an alarm. Powered by (1) 3-Volt CR2-Lithium battery (included), measures 7.19-inches high with a 2.5-inch radius and weighs only 0.18-pounds. UL Listed.