Quote Originally Posted by Tigerbeach View Post
Lottie, there are too many variables at play to really answer your question.

The simple answer is; I think you are asking if all tanks that have a full working pressure of 3000 psi hold the same amount of air, the answer is "no".

In this case the tank with the larger capacity should last the longest time underwater. However, there are many other variables at play.

Such as: Are the two tanks going on the same dive with the same diver?
If a man has a bigger tank than his female buddy, he might suck up more air and finish sooner. What depth are you diving? How hard will you be working? What is the water temperature?
All these can impact the bottom time with a tank of any size.
Well said! A single 72 has as much air as a closet. If you close the door and just sit there you will have a long time, but if you jump up and down and run in place, it won't last so long. The best thing I can tell you about air consumption is just dive a lot and become comfortable and you will be bringing extra air back!