I’ve had to explain this one more times than I can count.
[quote=“dovla, post:4, topic:8546”]It wouldn’t work. Scuba diving regulator is a fairly sophisticated piece of gear that controls pressure coming from the tank dynamically, depending on the ambient pressure. This allows the diver in non-pressurized suit to change depth and still be able to inhale (otherwise the pressure on the chest cavity would be too great and you’d suffocate). Medical oxygen regulator has none of that, just a simple valve delivering oxygen at a constant pressure (depending on how far you dialed it).
Perhaps it would work in a pinch if the dial on medical tank was open to overpressurize (i.e. dispense oxygen at greater than ambient pressure), but that would be a suboptimal solution. Also, breathing pure oxygen for prolonged period of time would not do you good (divers use a mixture of gasses in their tanks depending on how deep they go).[/quote]
This person has it right here.
There’s also this problem where this:
Is not the same as this:

Can y’all guess which one is engineered to keep air in while keeping water out?