Kidde CO Alarm: * Battery operated (3 AA batteries included): Provides protection during power outage * Battery lockout system: Deters covering battery compartment without installation of batteries * Slide-out battery door cover: Gives immediate access to batteries * Test/Reset button: Tests the unit for proper operation, resets the alarm * Low battery signal: Alerts user when the battery needs to be replaced * Green LED: Flashes every 30 seconds to indicate the unit is operating properly; also flashes before a 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