We all heard about a diver watch with a ‘Helium escape valve’. Besides the fact that we might know that it is a small ‘feature’ mostly at the 9 o’clock side (sometimes 10 o’clock), most people don’t specifically know what it means.
Well first we need to know that a helium molecule is extremely small. Under the right circumstances (like high pressure), helium can sneak past the seals of a watch where water molecules or the molecules of other gasses that make up our air can’t.
External pressure results in a helium build-up until that external pressure is released. If the helium can’t escape, the pressure continues to rise within and can result in a crystal blown off the watch. That kind of little ‘explosion’ will take your eye out. To prevent such an awful situation, a helium escape valve automatically depressurises the watch when it returns to a sea level pressure environment. It’s a one-way valve so it only lets pressure out of the watch. It’s designed to never allow water – with its larger molecule – to pass into the watch.