jb, going back to the QF 30 incident, in the ATSB report it says: "After clearing the baggage and cargo from the forward aircraft hold, it  was evident that one passenger oxygen cylinder (number-4 from a bank of  seven cylinders along the right side of the cargo hold) had sustained a  sudden failure and forceful discharge of its pressurised contents into  the aircraft hold." But from what I understand from this: "While it was hypothesised that the cylinder may have contained a defect  or flaw, or been damaged in a way that promoted failure, there was no  evidence found to support such a finding. Nor was there any evidence  found to suggest the cylinders from the subject production batch, or the  type in general, were in any way predisposed to premature failure." There has never been a clear picture as to what made this particular cylinder fail, has there? Are these cylinders in an area of the aircraft that is accessed by ground staff or only by mainteinance staff? Thanks for this amazing thread.