A fuel cell stack assembly (30) comprises a fuel cell stack (31); an air flow plenum chamber (33) disposed on a face (4) of the stack (31) for delivering air to or receiving air from flow channels in the fuel cell stack (31), at least a part of the plenum chamber wall being defined by a printed circuit board, the printed circuit board having at least one aperture (37) therein; and a fan (36) mounted to the board adjacent the aperture (37) and configured to force air through the aperture into or out of the plenum chamber. The assembly provides integration of circuit boards essential or supportive to operation of the fuel cell assembly with the air flow plenum for forced ventilation of the fuel cells in the stack.