Mech-prentice -- Assuming the cylinder ruptured prior to the hull breach then Volume 2 would be the pressurized fuselage, which was closer to 12 psi.
What about the potential energy?
The cylinder should have contained 3,260,000 cc (115 cubic feet) Oxygen @ 128 barg (1850 psig), 21 deg C (70 deg F).
Generally, for a diatomic gas whose volume is V, the internal energy is (1.4)PV
1.4 * 128 * 3,260,000 = 584,192,000 cubic cm-atm
...............................= 59,193,254 joules
...............................= 8 kg dynamite
.
Corrections are invited!