Combo Smoke and Carbon Monoxide Detector Battery Operated Co Smoke Alarm Detector with LCD Display

Product Feature High-tech sensor High accurate electrochemical sensor(the most accurate CO sensor) infrared photoelectric sensor(the bestsensor to detects smoke while minimizing false alarms) LCD concentration PPM   Easy to Install Battery Operated for Convenience 3*1.5V AA dry battery (package notinclude) -After installing 3 batteries, you can hear the sound of "di", and it starts working normally after 2 minutes. In operation, it displays nothing with a power-saving design. Ultra-long standby time, low current consumption -Press the button “test”, smoke and carbon monoxide detector alarms ?85db, loud enough to alarm you the dangers no matter you’re asleep in 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 plastic grommets into holes with a hammer. Mount the bracket to the ceiling by inserting and tightening the supplied screws into plastic grommets. TIPS: Please install the sirens at 0.3~1m below the ceiling because the concentration of carbon monoxide and smoke is smaller than that of air. Sound & Flash Alarm& LED indicating Alarm Combo Detector You can save money by buying a co smoke alarm while keeping yourself safe.   Specifications Item size 4.7 x4.7 x 1.8 inches Item Weight 6.4ounces accessory products main engine×1?Instructions×1?Screw( installed on the wall)×2 rubber stopper×2 (tips: it is without 3*1.5v AA dry battery?