PURPOSE: To supply warm air and water into which heat amount held by fuel is converted by introducing heat into wind to make hot wind and also constructing the wall of a furnace as a double-wall to make a warm water storage tank in it.

CONSTITUTION: Chaff or sawdust is used as fuel and transferred into a powder fuel vessel 16 after being crushed into powder form by a crusher 15. Fuel transferred from the powder fuel vessel 16 is controlled in quantity by a valvate 19 and then injected into the furnace inside from a powder burner 20 and ignited by an ignition oil burner 21 and controlled by a temp. sensor 22 for a burning chamber. When temp. in the burning chamber reaches a specified temp., the ignition oil burner is automatically extinguished and burning is continued by only powder fuel and operation is continued by the control of a warm water sensor 24. On the other hand, fresh air taken in by a warm air blower 1 and warm air heated by an air heat exchanger 2 is supplied from a warm wind outlet hole 3. The outside part 8 of the furnace body surrounding the burning chamber 7 inside stores water as a double-wall structure and water is warmed up and made into warm water when fuel is burnt in the burning chamber 7 and warm wind is generated.