A method and apparatus is provided for activating a carbon monoxide detector. The method includes the steps of the carbon monoxide detector measuring a current carbon monoxide level, the carbon monoxide detector comparing the current carbon monoxide level with a first threshold value, determining whether the current carbon monoxide level exceeds the first threshold value, entering an alarm state upon detecting that the current carbon monoxide level exceeds the first threshold value after a first predetermined time period, determining from memory whether the carbon monoxide detector had previously been in an alarm state before activation and upon detecting that the current carbon dioxide level does not exceed the first threshold and the carbon monoxide detector was previously in the alarm state, resuming the alarm state after a second predetermined time period.