PURPOSE: To reintroduce unburnt gas into a combustion chamber for combustion and reduce the CO/CO2 sharply during weak combustion by installing an inhibiting cylinder which extends upward from the lower part of a red hot section outside an outside flame cylinder and has a ventilation hole on a wall surface, and installing a plate between outside flame cylinders at a position lower than the red hot section.

CONSTITUTION: When a wick 1 is ignited, high temperature combustion gas produced by combustion rises in a combustion chamber 8 and hence produces heat draft so that the air supplied from a space between an outside flame cylinder 7 and an outside cylinder A9 is divided into a stream marked with the arrow (a) supplied to the combustion chamber 8 from an air hole 11 of a vaporizer 16b and a stream marked with the arrow (b) supplied to an air passage 20 by way of a reducing part 15. The fuel vaporized from the wick 1 by the air stream (a) rises as indicated by the arrow (c) in the combustion chamber 8 while a part of the fuel spreads and flows out into an inhibited area 25 as marked with the arrow (d), but unburnt gas is inhibited to spread and flow out into a space between an inhibiting cylinder 24 and an outside cylinder B18, thereby introducing the gas into the combustion chamber 8 from the air passage 20 between the inhibiting cylinder 24 and the outside cylinder B18 by way of a ventilation hole 26 for the inhibiting cylinder 24. The unburnt gas which flows out into the inhibited area is arranged to be introduced into the combustion chamber again, which makes it possible to sharply reduce the amount of CO discharged into the atmosphere.