A system for surveillance of a delimited area within which people move, wherein at least one hollow optical fiber is configured for extending through the area and is provided throughout its length with a plurality of holes that set an internal channel of the fiber in communication with the outside of the fiber itself. There is provided an optical source configured for supplying the optical signal to one end of the hollow optical fiber and a sensor designed to detect at one end of the hollow optical fiber the optical signal transmitted throughout the length of the fiber itself. A processing unit is configured for examining the spectrum of the optical signal detected by the sensors in order to detect the presence of toxic agents present in the area and drawn into said channel.