In the 1960’s a company called Comex was contracted to do undersea welding on North Sea oil platforms. The divers were supplied ROLEX watches. Now working so deep, each diver had to spend 4 hours each dive in the decompression chamber. This cut down productivty so Comex built a deep sea underwater dwelling which divers could stay down in and operate from. They would then work on a one week on one week off basis.
Everything went swimmingly (excuse the pun) except for one thing…when they resurfaced and enterred the decompression chamber after a week under sea, the crystals on the ROLEX would effectively blow off.
ROLEX investigated and found that Helium was being pumped into the undersea dwelling to fascilitate better absorbtion of oxygen (not sure of technical reason). Helium being one of the smallest molecules in the world (smaller than oxygen) was penetrating the ROLEX seals. This was not a problem until it came to decompression and the Heliums expansion within the watch led to the crystals explosion.
The solution…The ROLEX Sea Dweller with Manual Helium release valve which was opened during decompression.
If you are a normal diver you will never have to use it. The only time when it will become necessary is when you have been subject to a helium injected environment ie extreme depths.
Mooi nutteloos zoon heluim valve maar wel cool