Features:Loud 85 decibel alarm. The alarm sound pattern is four short alarm beeps. The red LED will flash while in the alarm mode. One chirp every 30 seconds in an indication that the battery is low (need replacement) (green LED still flashes once every 30 seconds). Test/Reset button to test the unit electronics and verifies proper unit operation and reset the unit during CO alarm. Alarm memory feature: If the unit ever alarms， pressing the button， green LED will flashes once every second for one minute and the peak alarm level will be indicated on the LCD. Green and red LED lights that indicate normal operation and alarm status. The unit will sound chirp and red LED flashes once as power up. Error display: "Err" prompt alarm failure ; "Lb" low voltage need to replace the battery. The carbon monoxide alarm pattern is 4 short beeps， followed by 5 seconds of silence， followed by 4 short beeps with a corresponding red LED flash. This cycle will continue for 4 minutes and then change to 1 cycle every minute until the device is reset or the CO is eliminated. Green LED: Flashes every 30 seconds to indicate the unit is operating properly. The green LED will also flash before CO reading is taken and when any button is pressed. Red LED: When a dangerous level of carbon monoxide is detected the red LED will pulse and a loud alarm pattern will sound. Specifications: Power Supply 3 pcs 1.5V AA size batteries (not included)Sensitivity & Time 50ppm， alarms within 60~90 minutes 100ppm， alarm within 10~40 minutes 300ppm， alarms within 3minutesSensitivity Range ＜2.5mStandby Current <50uAAlarm Current <50mAOperation Ambient Condition 5~40oC， 20~90%R.HCAUTION: This alarm will only indicate the presence of monoxide at the sensor. Garbon monoxide gas may present at other area. Package Including:1 X Carbon monoxide Poisoning A burglar alarm