A perfect item for protecting your family from the dangers of carbon monoxide * Advanced level of protection, easy to read with the digital display, even in low light conditions * Displays the level of carbon monoxide the unit is sensing * 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. 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.