HOT WATER BOILER

PROBLEM TO BE SOLVED: To reduce generation of bad smell at the time of quenching irrespective of the combustion rate by inserting, from inside of a flue to a combustion chamber, a baffle plate supporting a catalyst for subjecting uncombusted gas components to adsorption and combustion. SOLUTION: When combustion gas is flowed from a combustion chamber 2, uncombusted gas components which have been flowed to a flue 3 without being completely combusted at the time of quenching, are activated and combusted by a platinum catalyst held by a baffle plate 14 which is inserted into the flue 3 to weaken the smell. In the case of minimum combustion operation, the temperature of large percentage of exhaust gas does not reach the temperature for the platinum catalyst to activate and combust the uncombusted gas, resulting in exhausting uncombusted gas at the time of quenching. However, as a flat plate 17 is protruded to the inside of the combustion chamber 2, heat in the chamber 2 is absorbed and transferred to raise the temperature of the entire baffle plate 14 and the platinum catalyst activates and combusts the uncombusted gas components with the transferred heat and the exhaust gas heat. Thus the smell ascribable to the uncombusted gas is reduced even when a burner is quenched.