Abstract: A pressure actuated sealing system for a travelling grate comprising at least one horizontally elongated rigid seal plate pivotally mounted below said travelling grate in sealing relationship with said travelling grate and with windbox means mounted below said travelling grate, said travelling grate including a plurality of pallets each with seal plate engaging means and cavity means provided on the underside thereof, said seal plate being pivotable in the direction of movement of said travelling grate by engagement with said seal plate engaging means, said seal plate being pivotable in the direction opposite the direction of movement of said travelling grate by the pressure differential across said seal plate formed by the pressure of the gases within said wind box means on one side of said seal plate and the ambient pressure on the other side of said seal plate, said cavity means being adapted for permitting unobstructed pivotal movement of said seal plate in said opposite direction.