This smoke detector works on the principle that infrared scatters in the smoke to probe the smoke which is generated by the incomplete combustion at the initial stage of the fire. The smoke detector consists of photoelectric system, signal processing identification circuit and alarm circuit. The infrared scatters on the surface of the smoke when the smoke enters the darkroom of the detector, and then the photoelectric diode receives the scattered light and generates the photoelectric signal current. The photoelectric signal generates the alarm signal after being processed by the identification circuit, accordingly the purpose of alarming is achieved. For this smoke alarm, we promise 3 years quality guarantee. Specifications: Power supply: 9V battery Quiescent current: 6 ~ 12μ A Age limit of battery: 2 years Temperature: -10° C ~ +40° C Alarm decibel: ≥ 85dB/cbm Sensitivity of smoke: EN14604