【360 degree perception with high sensitivity】: Unique structure design and advanced photoelectric labyrinth, real-time monitoring of smoke presence, detecting visible particles faster than ionization alarm. 【Battery】: This smoke detector requires a 3V lithium battery (not included). 【Operation test button】: This smoke detector is equipped with a function test button for function test. This can reset the alarm detector after an alarm or return to monitoring mode. 【High quality and easy installation】: The outer casing of this smoke detector is made of high quality ABS + PC plastic, environmentally friendly and flame retardant. 【Comprehensive protection for your safety】: The smoke detectors have a built-in buzzer. Once the danger of smoke and fire is detected, the red LED indicator will flash immediately and an alarm tone of over 80 dB will sound to quickly remind you and your family.