I have been asked what the button at the 10 o’clock position actually did on the Omega Seamaster series of dive watches. It was a fair question so I thought about how I could explain to my work colleagues who really didn’t comprehend the complexities of helium in diving. I had heard of the helium escape valves on the Rolex Submariner dive watches and how the professional divers preferred these dive timepieces.

The purpose of the helium escape valve is due to the molecular structure of helium gas, the gas is 2.63 lighter than air. During deep decompression dives greater than 60 metres, various helim mixes are utilised with commercial divers spending extended time at depth. During the dive (compression) phase divers are at depth, they enter and exit a diving bell that is held at the same pressure as the surrounding water pressure. During the dive phase, the lighter helium gas is able to penetrate the seals and enter the timepiece.

During the decompression phase, the surrounding air pressure is reducing [gradually] allowing the gas absorbed in the diver’s bodies to diffuse out. The pressure differential between the surrounding pressure and the watch case can cause the crystal to pop out. To prevent this occurring, there is an internal valve that is either automatic [Rolex] or manual [Omega] allowing the gas to escape. This allows the pressure to equalise ensuring no damage occurs  to the timepiece.

Whilst this is a  requirement for commercial saturation divers,  professional divers such as dive instructors, dive guides or technical divers have no requirement for the helium escape valve but this remains a feature of professional dive timepieces. Even for most commercial divers, the helium escape valve is not required as depths and durations do not require such extended decompressions on the ocean bottom. Really this is more marketing than mechanics.