The present invention discloses a marking system (102) which detects an identifying feature (112) on an item (110) in a field of view (114), and creates a mark or annotation (204, 208) on the item using a laser source (120). While the marking process commences, the system monitors the field of view to detect if the field of view changes in an unacceptable way. Such unacceptable changes include if the item is removed from the field of view or if the field of view has become obstructed (712), potentially creating an unsafe exposure to the laser source. Upon detecting such a condition the laser source is shut down (718) within a prescribed period of time to prevent an unsafe exposure.