US Patent 7784221 Fire collar

A fire collar (10) including a housing defining an opening (18) and a passage (20) adapted to receive a conduit therethrough. A layer of intumescent material (43) surrounds the conduit and is supported by the housing adjacent the opening. Torsion springs (34) are mounted between the housing and the intumescent material to surround the conduit and are held in a non-operational position by fusible links (41). When the heat of a fire melts the links, each torsion spring acts in a longitudinal plane of the passage to assist the intumescent material to collapse the conduit and seal the passage against advancement of the fire.