Some watch manufacturers manage the internal overpressure effect by simply making the case and sealed connected parts adequately sealed or strong enough to avoid or withstand the internal pressure,[1] but Rolex and Doxa S.A. approached the problem by creating the helium escape valve in the 1960s (first introduced in the Rolex Submariner/Sea-Dweller and the Doxa Conquistador): A small, spring-loaded one-way valve is fitted in the watch case that opens when the differential between internal and external pressure is sufficient to overcome the spring force.
As decompressing saturation divers is a slow working conditions requirements regulated process to prevent sickness and any other harmful medical effects,[4][5] the helium release valve does not have to be able to cope with extremely rapid decompression scenarios, that can occur in a material/medical pass-through system lock.
Helium release valves can primarily be found on diving watches featuring a water resistance rating greater than 300 m (1000 ft).
On the initial and any later blowdown or compression, most saturation divers consciously open the water-resistant crown of their watches to allow the breathing gas inside to equalize the internal pressure to their storage/living environment.
ISO 6425 provides specific additional requirements for testing of diver's watches for mixed-gas diving.