To prevent the erosion of a seal packing and the leakage of water while securing an excellent water stopping function by the soft metallic seal packing.

The water discharging port 8 of a head main body 1 is closed by the seal packing 3, which is pressed to the port 8 via a packing presser 4 by a thermosensitive operation member 5 to be decomposed by the heat of a fire. The packing 3 is obtained by coating the outer surface of a soft metallic plate 10 such as a malleable copper plate with a fluororesin 11 excellent in water repellency and chemical resistance.