Carbon Detector, CO Detector Alarm LCD Portable Security Gas CO Monitor, Battery Powered Co Detector, Carbon Monoxide Detector (3 AA Battery not included) Dr.fasting co detector protect your family from the dangers of carbon monoxide,Battery-operated alarm that includes a blue back light digital display feature. 2. Whenever dangerous levels of CO are present, red LED will flash and the alarm pattern will sound, Loud 85 decibel alarm. 3. Low battery signal and "end of life"warning ensures detector is ALWAYS monitoring your safety. 4. It is very convenient for us to install and operate. 5. Operated by 3 x 1.5V AA Batteries (not included), Green and red LED lights that indicate normal operation and alarm status.