NOVELTY - An anode bleed from anode side of first (12) and second split stacks (14) is triggered by determining concentration of nitrogen in anode side of first and second split stacks; determining maximum cell voltage of fuel cells in first and/or second split stacks; determining minimum cell voltage of fuel cells in first and/or second split stacks; determining average cell voltage of fuel cells in first split stack; determining average cell voltage of fuel cells in second split stack; and commanding anode bleed.    USE - Method for triggering anode bleed from anode side of first and second split stacks that operate by anode flow-shifting.    ADVANTAGE - The method employs anode flow-shifting. The concentration of nitrogen in anode can be determined in any suitable manner.    DETAILED DESCRIPTION - The anode bleed from anode side of first (12) and second split stacks (14) that operate by anode flow-shifting is triggered by:    (A) determining concentration of nitrogen in anode side of first and second split stacks;    (B) determining maximum cell voltage of fuel cells in first and/or second split stacks;    (C) determining minimum cell voltage of fuel cells in first and/or second split stacks;    (D) determining average cell voltage of fuel cells in first split stack; determining average cell voltage of fuel cells in second split stack; and    (E) commanding anode bleed if concentration of nitrogen in anode side of first and second split stacks is greater than predetermined threshold concentration; difference between maximum cell voltage and minimum cell voltage is greater than predetermined spread voltage; or absolute value of difference between average cell voltage of fuel cells in first split stack and average cell voltage of fuel cells in second split stack is greater than predetermined bounce voltage.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic block diagram of a fuel cell system.    First split stacks (12)    Second split stacks (14)    Bleed valves (50, 52)    Water separator (60)    Purge valve (66)