Abstract: The device (80) described can be used in universal fashion for the intermingling, relaxing, and/or thermosetting of filament yarn (50) in a melt spinning process. It comprises a treatment chamber (80, 81), which is capable of being filled with a gas under essentially static overpressure and increased temperature, and features an intake aperture (83) and an outlet aperture (84), designed for preference as nozzles, for the passage of the yarn (50), through which the gas can flow, under pressure relief, respectively in or against the direction of the run of the yarn (50).