in close contact with the membrane electrode assembly further an anode electrode hereinafter referred to as an u201c anode u201d is provided at one surface of the membrane electrode assembly and a cathode electrode hereinafter referred to as a u201c cathode u201d is provided at the other surface of the membrane electrode assembly in addition an electrolyte membrane is provided between the anode and the cathode the anode ionizes the fuel supplied through the channel of the separator into electrons and hydrogen ions by an oxidation reaction and the electrolyte membrane transports the hydrogen ions to the cathode the cathode generates water and heat though a reduction reaction between the electrons and the hydrogen ions supplied from the anode and oxygen in the air supplied through the channel of the separator an air exhaust line 14 can further be in connection with the cathode of the stack 30 such that the air going through the chemical reaction is exhausted to the exterior of the vehicle through the air exhaust line 14 in addition nitrogen which is in the air supplied to the cathode of the stack 30 penetrates the electrolyte membrane and passes to the anode to thereby increase nitrogen concentration in the anode if the nitrogen concentration in the anode increases to certain levels diffusion of the hydrogen is hindered therefore it is preferred that nitrogen in the anode be removed further a portion of the water generated in the cathode by the chemical reaction.