Flight Deck Since the flight deck requires only a fraction of the air supply provided by the left pack, most of the left pack air output is mixed with the right pack supply and routed to the passenger cabin. Conditioned air for the flight deck branches into several risers which end at the floor, ceiling, and foot level outlets. Air diffusers on the floor under each seat deliver continuous air flow as long as the manifold is pressurized. Overhead diffusers are located on the flight deck ceiling, above and aft of the No. 3 windows. Each of these outlets can be opened or closed as desired by turning a slotted adjusting screw. There is also a dual purpose valve behind the rudder pedals of each pilot. These valves provide air for warming the pilots feet and for defogging the inside of the No. 1 windshields. Each valve is controlled by knobs located on the Captains and First Officers panel, respectively.