Light and Sound Alarm Warning: When a dangerous level of carbon monoxide is detected, the red LED will flash and the alarm model will emit an 85 decibel alarm to protect your family's life and property safety from the CO detector. Alarm Standard: The alert time depends on the carbon monoxide concentration level. 50 ppm, alert within 60-90 minutes; 100 ppm, alert within 10-40 minutes; 300 ppm, alert within 3 minutes. High-quality carbon monoxide detector, equipped with a high-precision and reliable long-life electrochemical CO sensor to quickly detect CO gas leaks: Power supply: (DC3V) 2AAA size batteries. (Not Included) Sensor Type Electrochemical Gas Detection Type: Carbon Monoxide Material: ABS LED Indicator Operation Green LED: Green LED flashes every 40 seconds to indicate the unit is working properly Red LED: When a dangerous level of carbon monoxide is detected, the red LED flashes and the alarm sounds LCD Display Solubility: 000-999PPM “Lb” on the LCD display indicates low