" Warning light and sound alarm: When a dangerous level of carbon monoxide is detected, the red LED flashes and the alarm model emits an 85 decibel alarm to protect your family's life and property safety from the CO detector. Standard alarm: 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 accuracy and reliable long life electrochemical CO sensor to quickly detect CO gas leaks: Power supply: (DC3V) 2AAA size batteries. (Not included) Sensor Type Type Electrochemical Gas Detection TypeCarbon Monoxide Material: ABS LED Indicator Operation Green LED: Green LED flashes every 40 seconds to indicate unit is working properly Red LED: When dangerous level carbon monoxide is detected, red LED flashes and alarm sounds Solubility of LCD display: 000-999PPM Lb on LCD indicates low battery (requires replacement) "