A helium release valve, helium escape valve or gas escape valve is a feature found on some diving watches intended for saturation diving using helium based breathing gas.
An integrated, automatically operating helium release valve as used by Rolex for the Rolex Sea-Dweller Deepsea variant.
An integrated, automatic helium release valve (at lowermost point of casing) as used by Breitling for the Avenger Seawolf.
A manually operated (screw crown principle) helium release valve as used by Omega SA for their Seamaster dive watches, here the Planet Ocean.
A manually operated helium release valve as used by Enzo Mechana for their entire line of dive watches. Pictured is the EM001 "Sub Hatch"
A diving watch, also commonly referred to as a diver's or dive watch, is a watch designed for underwater diving that features, as a minimum, a water resistance greater than 1.1 MPa (11 atm), the equivalent of 100 m (330 ft). The typical diver's watch will have a water resistance of around 200 to 300 m, though modern technology allows the creation of diving watches that can go much deeper. A true contemporary diver's watch is in accordance with the ISO 6425 standard, which defines test standards and features for watches suitable for diving with underwater breathing apparatus in depths of 100 m (330 ft) or more. Watches conforming to ISO 6425 are marked with the word DIVER'S to distinguish ISO 6425 conformant diving watches from watches that might not be suitable for actual scuba diving.
Breitling Avenger Seawolf, with a water resistance of 3,000 m (10,000 ft). The round feature on the watch case side at 9 o'clock is an integrated helium release valve.
The vintage 1936 California Dial Radiomir Panerai
US Marine diver with a diving watch and an analog depth gauge
Seiko 7002-7020 Diver's 200 m