Originally Posted by
Flight Alloy
Nope, 787 uses O2 bottles both for flight deck and cabin oxygen systems. Each 3 seat group shares one oxygen bottle in the bulkhead overhead, fired by a pyrotechnic valve when operated. These valves, by definition single use, can not be tested, and are the source of failures.
I wonder what the failure mode of the valve is. Open circuit in the squib (electric match)? Bad or weak pyrotechnic charge?
The squib circuit should be testable for continuity non-destructively. It's what demolition pyrotechnicians do prior to setting off a group of charges to bring a building down. The failure of some could result in the structure falling in an uncontrolled manner. I would be seriously surprised if the O2 system did not incorporate such a built-in-test (BITE).
Pyrotechnics themselves are pretty reliable, assuming that they are built with some quality control in mind. And if a suitable level of reliability can't be achieved, either redundant charges or a manual backup to open the O2 valve might be needed.