Combustion apparatus

1. A combustion apparatus comprising:

a burner for combusting fuel gas to generate combustion exhaust gas;

a heat exchanger for recovering heat in the combustion exhaust gas to heat a heat medium, the heat exchanger being accommodated in a casing having a substantially quadrangular box shape;

an exhaust passage for discharging the combustion exhaust gas from an exhaust port, the exhaust passage being provided to one side surface side of the casing; and

an exhaust resistance member having a plurality of ventilation ports through which the combustion exhaust gas passes and being provided beneath the heat exchanger, wherein

the burner, the heat exchanger, and the exhaust passage are arranged in such a manner that the combustion exhaust gas flows from top to bottom through the heat exchanger in the casing, and further from beneath the casing to the exhaust port via the exhaust passage provided at the one side surface side of the casing, and

at least one part of the ventilation ports of the exhaust resistance member has an elongated hole shape extending in the flow direction of the combustion exhaust gas from beneath the casing to the exhaust passage.

2. The combustion apparatus according to claim 1 , wherein

one end of the ventilation port farther from the exhaust passage has a wider width than other end of the ventilation port closed to the exhaust passage.

3. The combustion apparatus according to claim 1 , wherein

the exhaust resistance member has a downwardly recessed shape or a inclined shape so that any one of ends of the ventilation port is positioned downward.

4. The combustion apparatus according to claim 1 , wherein

at least one part of the ventilation ports has a different size from at least one other part of the ventilation ports.

5. The combustion apparatus according to claim 1 , wherein

a long edge of the ventilation port has a circular-arc shaped surface curved downward from an upper surface of the exhaust resistance member.