5 Pack Smoke Detector Carbon Monoxide Detector Combo Battery Powered,Carbon Monoxide Detector Smoke Alarm with Test Button,Smoke and Carbon Monoxide Detector with Digital DisplayBrand: OLUNCLE Color: White 5 Features: This smoke detector carbon monoxide detector combo adpots photoelectric sensor and electrochemical CO sensor, it is a 2 in 1 carbon monoxide and smoke detector, so you don't need to install them separately Smoke and carbon monoxide detector has a readable and large digital display. But to save power, the display is not always on. Under normal working state, only the green led light will blink every 60 seconds or