FUEL CELL SYSTEM, MOBILE OBJECT, AND EXHAUST GAS DISCHARGE CONTROL METHOD

A fuel cell system mounted in a mobile object is equipped with a bypass flow passage that establishes communication between an air compressor and an exhaust gas flow passage, and a valve that adjusts an amount of air supplied to the bypass flow passage. A control unit performs a process for increasing a flow rate of air caused to flow through the bypass flow passage, by controlling a drive amount of the air compressor and the opening degree of the valve, when an outside air temperature is equal to or lower than a threshold and a speed of the mobile object is equal to or lower than a determination speed. In the process, a flow rate of air at a first temperature that is lower than a second temperature that is equal to or lower than the threshold is larger than a flow rate of air at the second temperature.