I was thinking along those lines too. A 46" high nitrogen tank holds around 125 cubic feet. As a wild guess, if an ATM contains 5 cubic feet of air then you c

I was thinking along those lines too. A 46" high nitrogen tank holds around 125 cubic feet. As a wild guess, if an ATM contains 5 cubic feet of air then you could completely change the air 25 times with one tank. Does that sound reasonable?