Fuel cell system

A fuel cell system comprising:

• a hydrogen generator configured to cause a reforming reaction of a material gas to generate a hydrogen-containing fuel gas;
• a fuel cell configured to cause a reaction between the fuel gas generated by the hydrogen generator and an oxygen-containing oxidizing gas to generate electric power;
• a combustor configured to combust at least one of the material gas and an off fuel gas discharged from the fuel cell;
• a casing configured to accommodate the hydrogen generator, the fuel cell, and the combustor;
• a flue gas passage through which a flue gas generated by the combustor is discharged;
• a first exhaust port, which is formed on the casing as a tip end opening of the flue gas passage and through which the flue gas from the combustor is discharged to an outside of the casing;
• a first intake port formed on the casing;
• a suction unit configured to suction air through the first intake port into the casing;
• and
• a CO detector provided at a place in the casing but other than the flue gas passage and configured to detect carbon monoxide contained in the air suctioned by the suction unit through the first intake port into the casing, wherein
• air is directly sent to the CO detector through the first intake port.