# Gas Cylinder Life

Say I have a gas cylinder filled with nitrogen to some volume at some pressure. On that cylinder I have a regulator so that I get a steady pressure out. I wish to discharge the cylinder. How many hours until that cylinder is exhausted?

I would assume the 'new volume' would be Vl=(Ph*Vh)/Pl. However, I don't understand how the flow rate is determined.

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If pressure is constant, then how do you have two variables, Ph and Pl that represent pressure? There would be two volumes, the difference between them is the volume extracted. Flow rate is volume extracted times density over time. Oh, and your regulator has to do work. –  AlanSE Jul 24 '12 at 17:21