What is the Gas (or Helium) Escape Valve on the Sea-Dweller for?
Note: I am not a diver, so I don’t know anything about this. In saturation diving divers are kept at extreme pressure for extended periods of time. This allows the divers to spend more time working at great depths without having to go through decompression between dives. The high pressure gas (frequently mixed with Helium) will naturally seep into the watch as the crown is unscrewed and due to the small size of helium molecules. When decompressing, the high pressure inside a watch can cause its crystal to pop off, as the watch was designed to take external pressure, not internal pressure. The Sea-Dweller has a spring-loaded valve on the side of the case that will automatically open if internal pressure is considerably higher than external pressure. The Omega Seamaster also has a helium escape valve that is at its 10 o’clock position but it is manually unscrewed.
