Fire stop for ventilation duct

摘要

The fire stop (18) moves vertically in a gap (17) in a double-walled sector of the duct (12). It is held open at normal temperatures, connecting two line sectors, but moved down at a higher temperature to close off the sector. It is held in the gap between two metal sheets curved to match the duct, and is similarly curved so as to be held to one sector until moved down to close off the section of a branch duct run radially off the main one. The movement of the stop is effected by a fusible solder mass (19) or bob which melts between 60 deg C and 80 deg C. The fire stop is made of a fireproof material of sufficient thickness to prevent the fire spreading from the main to the branch duct, and can also be made of sheet metal, specifically coated on one or both sides with foam swelling under heat, assisted by foam spread round the inner wall of the branch duct so as to swell under heat and close off the connection.