Abstract: An air duct system for use with mining machines in dust collection systems is connectable between a suction source and the cutting area of a mining machine and has two duct sections movable relative to each other. One duct section is mounted on the cutter boom of the mining machine and has an extendable upper wall, connected through a hinged plate, that abuts a wall of the first duct section which is mounted on the mining machine body. A lower hinged plate connected to the bottom wall of the duct swivels freely and rests on the bottom wall of the first duct to enclose the space between the two duct sections.