Abstract: The duct comprises an inner tube in which the wires are disposed, and this inner duct is placed inside an outer tube so as to provide a continuous inner space between the tubes, which completely surrounds the inner tube. A water inlet is in communication with the inner space and water is allowed to penetrate into the inner space upon the opening of a valve. The valve is operated by a fire detector. Upon activation of the valve in case of fire, water circulates through the inner space and is rejected into a drain. This system constitutes a fire and heat barrier for the wires of a building, for example.