[EN Certified] With carbon monoxide detectors, you will feel comfortable, safe and confident. [Ultra Loud Audible Alarm] The carbon monoxide alarm will detect carbon monoxide levels 24 hours a day. The alarm duration depends on the carbon monoxide level. 50-100 PPM, alarm after approximately 80 minutes, the red LED flashes every 2 minutes; 100-300 PPM, alarm after approximately 30 minutes, the red LED flashes every 2 minutes and emits a beep; >300 PPM, alarm after approximately 50 seconds, the red LED flashes rapidly and a continuous beep >86 dB. [Digital LCD Display] The LCD screen shows the CO concentration level in PPM, temperature, humidity and battery status. And three LED indicators show three working states: Red (alarm mode: the red LED flashes quickly, the buzzer emits a "beep beep beep" sound), Yellow (fault mode: the yellow LED flashes twice in about 60 seconds, accompanied by two "beep beep" sounds), Green (on, normal standby mode). [Carbon Monoxide Detector with