Carbon Monoxide Detector Battery Operated Co Alarm Detector with LCD Display

High-tech sensor High accurate electrochemical sensor(the most accurate CO sensor) infrared photoelectric sensor(the best sensor to detects smoke while minimizing false alarms) LCD concentration PPM Easy to Install Battery Operated for Convenience 2*1.5V AA dry battery (package notinclude) -After installing 2 batteries, you can hearthe sound of "di", and it starts working normally after 40s. In operation, it displays nothing with a power-saving design. Ultra-long standbytime, low current consumption. -Press the button “test”, carbon monoxide detector alarms ?85db, loud enough to alarm you the dangers no matter you’re asleepin the bedroom or watching TV downstairs. -So easy to install on wherever you stay for long periods: drill the two marked installation holes. Tap the two plasticgrommets into holes with a hammer. Mount the bracket to the ceiling byinserting and tightening the supplied screws into plastic grommets. TIPs in usages: -How to know it’s working normally:  The green power indicator flashes every 35s. -How to know it’s broken:  The yellow indicatoris always on, the LCD shows “Err” and the machine beeps “didi” every seconds. -How to know it’s time to change batteries: The yellow indicator lights 50ms every 35s and “di” at the same time. Please install the sirens at 0.3~1m belowthe ceiling because the concentration of carbon monoxide is smaller than that of air.   Specifications Item size 4.3 x4.3 x 1.4 inches Item Weight 3.8ounces accessory products main engine×1?Instructions×1?Screw( installed on the wall)×2 rubber stopper×2