Abstract: A rolling fire door consists of a plurality of interconnected fireproof slats forming a curtain which is received by a pair of tracks along the sides of an opening to be secured. A torsion spring assembly assists in the raising and lowering of the curtain during normal operation. A torsion spring tube, rotated by raising and lowering of the curtain, is connected to a hydraulic pump. Upon the sensing of smoke, fire or the like, the torsion spring mechanism is disengaged and the curtain begins to fall by its own weight within the pair of tracks. The falling of the curtain rotates the torsion spring tube and accordingly drives the hydraulic motor which includes a restriction providing a load to the rotation of the torsion spring tube, thereby restricting the rate of descent of the curtain.