A control strategy for removing nitrogen from the anode side of a fuel
cell stack. The control strategy includes using a bleed valve to remove
the nitrogen during the operation of the fuel cell stack until the stack
ages to a point where the bleed valve is maintained open, but the
concentration of nitrogen in the anode side of the stack continues to
increase. Once the concentration of nitrogen in the anode side increases
to a predetermined level, then a purge valve is opened in combination
with the bleed valve to reduce the concentration of nitrogen. Once the
nitrogen concentration is reduced below the level, then both valves are
closed, and the sequence is repeated.