Area surveillance with chemical sensors

A system for surveillance of an area in which people or goods move (for example, airport or sea-port terminals, railway stations, large department stores, shopping centres, industrial plants, etc.) or at specific locations sensitive for security of an internal area that are difficult to access, such as, for example, the air-intake and conditioning ducts, in order to detect in a timely way the presence of toxic agents or explosive precursors in the air.