Deepsea Challenge — why does it have a HEV?

[Sothy]

Since the new Deepsea doesn’t have a date, it’s not meant for living underwater. So since it’s not meant for saturation diving, why does it have a HEV? My understanding is that the Helium escape valve is only needed when doing saturation diving as opposed to (impossibly) deep scuba diving. Am I missing something?

(The use of titanium opens up some interesting design options for other models like the Explorer 2, but I still like steel and gold :-).