Hatches for Onions and Potatoes Air mixing unit with mix-hatches for inside/mix/outside air. Extension for extraction of air. Hatches executed in plywood with coating. Practical situation with mixing hatch. Info hatch position: 79% open. Setup page hatches. Status page hatches. Construction of wall for underground aeration. Fan in pressure chamber. Pressure wall made of plywood and horizontal beams. Bearing sheet for ax.