Help Nitrogen gas flow rate for scuba?

[Nocturna666]

This sounds like a ridiculous question but my mind is getting paranoid about what could possibly go wrong with ctb. When using a nitrogen cylinder for scuba do you have to turn the nitrogen tank cylinder nozzle all the way to release as much gas flow as possible or does the mask (Neptune III) automatically sort that out and pressurize it for you? I understand Neptune III has a built in regulator but the actual flow itself is what's confusing me being I don't have experience with cylinders themselves other than for this reason.

Thanks for any insights