A method for monitoring an area includes distributing, by a detector unit, light during a first instance of time in order to characterize the area based on first data associated with the first instance of time; distributing, by the detector unit, light during at least a second instance of time in order to obtain second data; comparing a first portion of the second data to at least one of: a second portion of the second data and the first data; and based on the comparison, signaling an alarm condition by the detector unit when an evolution in the second data is detected in an amount greater than a threshold.