Fuel cell system

A fuel cell system comprising:

• a fuel cell for generating electricity using a hydrogen gas and an oxidant gas as a reaction gas;
• a hydrogen discharge unit for discharging hydrogen from the fuel cell under a predetermined condition;
• a hydrogen concentration reduction process unit for reducing the concentration of hydrogen discharged from the hydrogen discharge unit;
• a hydrogen concentration detection unit for detecting an instantaneous hydrogen concentration of a gas processed by the hydrogen concentration reduction process unit;
• and
• an average hydrogen concentration calculating unit for calculating an average hydrogen concentration per hour of a gas processed by the hydrogen concentration reduction process unit, wherein
• a hydrogen discharge from the fuel cell by the hydrogen discharge unit is prohibited in the event that an instantaneous hydrogen concentration detected by the hydrogen concentration detection unit exceeds a first threshold, or in the event that an average hydrogen concentration calculated by the average hydrogen concentration calculating unit exceeds a second threshold which is lower than the first threshold.