The 744 passenger oxygen bottles feed into a common manifold. Each bottle has a pressure relief valve (or rather, frangible disc) which allows the bottles' contents to discharge overboard if the internal pressure is too high. The pressure required to activate this relief valve is significantly higher than the typical system pressure (1800psi), but presumably far lower than the pressure required to rupture a serviceable bottle
To change a pax bottle on a Qantas 744, you have to close all the other bottles, both in the right hand (Fwd) cargo sidewall and in the (Fwd) cargo ceiling.
Unless I have overlooked something obvious, if one of the bottles ruptured, I would say that the contents of the entire system would start venting. Question to experts: Do the pressure reducers shown in the Boeing Schematics (35-11-00) have inbuilt check valves?
On this type of pax oxygen system, the bottles feed 3 flow-control units. These allow the oxygen to get to the passengers (after being activated by various manual and automatic methods).
The oxygen masks drop from the overhead panels via doors which are unlatched by the oxygen pressure surge coming down the lines. Clearly in the videos, the masks have dropped. Ergo... at least some pressure was present. See other PPRuNe message threads for interesting information on the effectiveness of pax oxygen systems. Once the door has released and the mask has dropped, the passenger has to physically pull down on the mask (to allow oxygen to flow from the overhead unit)
I wonder how many of the passengers remembered to pull down on the oxygen masks after paying careful attention to the preflight safety demonstration? There is, of course, automatic announcements during a decompression to remind them
Rgds.
NSEU