Any inert gases or contaminants accumulate in and around the porous anodes and reduce the reaction efficiency and electrical load support capability. Therefore, this mode requires a high purity hydrogen fuel (e.g., >99.99%). In addition, water films and droplets are often found on the anode due to vapor condensation and back-diffusion of product water fromthe cathode. However, in this mode, hydrogen is supplied at the exact rate required by the fuel cell stack, for an anode stoichiometric ratio that is equal to or slightly less than one. Because of a lack of forced convection in the dead-end mode, the liquid water is prone to accumulate in the anodes, which eventually causes flooding and deterioration of the cell performance in the form of a decline in the voltage