A helium escape valve is a small, spring-loaded one-way valve set into the case of some dive watches. It lets pressure that has built up inside the watch vent out. Helium trapped in the case can damage the watch when a diver decompresses, for example by forcing the crystal off.
How does a helium escape valve work?
Helium atoms are very small. Over a period of roughly five days, they can work their way inside a watch case. Once inside, the gas is trapped. As the diver decompresses, that trapped helium can damage the watch, and the crystal can be forced off. The valve gives the gas a way out. A spring holds it shut. It works in one direction only, so pressure that has built up inside can vent to the outside.
Where it comes from
Rolex and Doxa developed the helium escape valve in the 1960s. Robert A. Barth, a US Navy diver, is credited with first thinking of using a one-way valve. Rolex filed its patent for the valve on 6 November 1967. The patent was granted on 15 June 1970. In 1969 Doxa released the SUB 300T Conquistador. It is described as the first dive watch with a helium release valve that the public could buy. Rolex’s first watch with the valve was sold only to commercial diving firms such as COMEX.
Do all deep-diving watches have one?
No. The valve is found mostly on dive watches rated for depths greater than 300 metres. Some makers, such as Seiko and Citizen, make their dive watches without it. They protect those watches against mixed-gas diving in other ways. Instead of a valve, these watches usually rely on special gaskets and a one-piece case, known as a monocoque case.
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