To obtain high durability and heat resistance so as to be usable in a high-temperature high-humidity atmosphere by integrally forming an impeller of PBT(polybuteneterephthalate) resin with glass fiber mixed therein.

Fuel gas and air blasted by an air blasting fan are mixed in a burner part, burnt in a combustion chamber and heat-exchanged with water in a heat exchanger provided at the combustion chamber, thus heating water. In a gas water heater or the like of such constitution, a sirocco fan is provided with an impeller 4 of the air blasting fan composed of a disc-like base 4a, a large number of blades 4b arranged in cylindrical shape at one side face of the base 4a, and a boss part 4e provided at the central part of the base 4a so as to fit the impeller 4 to a rotary shaft 5a of a fan motor 5. The impeller 4 is integrally formed of PBT(polybuteneterephthalate) resin with glass fiber mixed therein. The impeller 4 is therefore excellent in durability and heat resistance and underformed by water absorption so as to be safely usable for the air blasting fan for the gas hot-water feeder or the like.