Étiquette  Helium escape valve

Helium escape valves are found on dive watches normally intended for saturation diving, where divers breathe a mixture of oxygen and helium. The extremely small helium atoms may enter a watch. During decompression, their volume increases, creating an internal pressure that can cause the crystal to pop off. Helium escape valves are one-way, usually spring-loaded valves that allow these atoms to be released when the internal pressure reaches a certain level.