Why were there different handles on the air manifold?

This was done so that the operator could tell them apart even if the control room was dark or full of smoke. To qualify to stand this watch, the operator was blindfolded and he brought the boat to the surface. In normal operation, the different shapes also provided confirmation that the operator had the desired valve handle.

This was also true for the vent valve handles at the chief of the watch’s station. Like the valve handles on the air manifold, it allowed the chief of the watch to tell them apart even if the control room was dark or full of smoke. In normal operation, the different shapes provided confirmation that the chief had the desired valve handle.