1. A system comprising: at least one processor; at least one 3D camera, in communication with the at least one processor; and computer executable instructions readable by the at least one processor and operative to: use the at least one 3D camera to visually observe a number of persons in a space, relying on object recognition computer executable instructions to determine a number and/or identity of persons in the space, wherein the object recognition computer executable instructions performs: image detection in the space, thermal detection in the space, detection of audio of persons in the space, counting the number of persons in the space, and analysis of data captured by the at least one 3D camera; compare the number of persons that are determined to be in the space with a number of persons authorized to be in the space, wherein the comparison depends on the number of authorized persons that should be in the space as specified by a number stored in a database, wherein the number of persons authorized to be in the space is selected by a user of the system; trigger an alarm if the number of persons determined to be in the space exceeds or does not correspond to the number of persons authorized to be in the space; and allow the number of persons authorized to be in the space to be changed if the number of persons in the space does not match or exceeds the number of persons authorized to be in the space.