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The US Navy Helium Helmet Exhaust Valve(s)

The US Navy Helium Helmet Exhaust Valve has two versions. The early helmets had a exhaust duct which ended in a bulb just like the banana tube. This duct rose vertically from the main body over the top of the helmet and terminated near the elbows. It was found that salt water could leak back into the helmet. If this water were to mix with the CO2 absorbent it would form chlorine gas. In the early 1950's the design was changed to add an additional non-adjustable double exhaust valve on the top of the helmet. This in essence made the valve a "triple exhaust". The primary valve is a standard Mark V assembly.