Smoke and Carbon Monoxide Detector with Batteries,2-in-1 Smoke Detector Carbon Monoxide Detector Combo,Smoke and Carbon Monoxide Alarm with Test Button and Digital DisplayBrand: LEMONTAIL Features: Dual Sensors: This combination smoke carbon monoxide alarm detects both smoke and carbon monoxide. It's working method: a high sensitivity photoelectric sensor to detect smoke and high stability electrochemical co sensor to detect carbon monoxide. They are separate, no matter which sensor is triggered because of dangerous concentration, this smoke and carbon monoxide detector will beep and blink with red led Loud Beep: This