Features of the Rolex Sea-Dweller
The Helium Escape Valve
Before they return to the open air, professional divers heading for the surface after a deep saturation dive must spend time in a decompression chamber, where they breathe a gas mixture containing helium. The tiny molecules of helium, an extremely light gas, infiltrate into the watch. During decompression, the helium is unable to escape from the waterproof case quickly enough, creating a pressure differential that could force the crystal out of the watch case. Rolex engineers created a gas escape valve fitted with a spring: it opens when the difference in pressure between the inside and outside of the watch reaches 3 to 5 bars, allowing the helium to escape, thereby protecting the watch.