Passenger oxygen generators?

[Will]

I was reading about the 1996 DC-9 crash, ValueJet 592, in which improperly stored chemical oxygen generators likely ignited a fire that led to the accident.

The chemical oxygen generators carried on the accident flight were for MD-80s, which had them outfitted above every passenger seat. A trap door releases an oxygen mask, which is connected to a wire that ends in a pin that blocks the firing pin of the oxygen cylinder, much like the pin of a hand grenade keeps it from exploding. Pulling the mask removes the pin, and that lets the oxygen generator's firing pin strike a percussion cap, which initiates a chemical reaction: in the presence of heat, sodium chlorate is reduced to sodium chloride, liberating oxygen (2 NaClO3 → 2 NaCl + 3 O2). This reaction, exothermic, continues as long as both heat and and sodium chlorite are present. The oxygen passes through a series of filters and into the passengers' masks. Meanwhile, the outside of the generator can heats up to about 500ºF.

Imagine several hundred of these in the cabin of an aircraft. Fascinating.

Ironically perhaps, the DC-9 didn't use chemical oxygen generators, so the ones that were being ferried on ValueJet 592 were for other aircraft (MD-80s) in the fleet.

This raises a few questions for the experts out there.

How common was this idea? Seems like it wasn't the original solution to the passenger oxygen problem, since the DC-9, which didn't use chemical oxygen generators, predated the MD-80, which did.

Looks like the 747-400 stores the passenger oxygen in tanks, and we can read the pressure in the system on the EICAS Status display. Where are the passenger oxygen tanks? How many are there? Has anyone ever worried that structural failure might rupture the passenger oxygen lines, venting the oxygen out uselessly at exactly the moment it is needed in an emergency descent?

What are the newest aircraft these days doing for passenger oxygen?

[Jeroen Hoppenbrouwers]

Oh there are much more interesting failures of oxygen tanks.
The tanks are here:
https://en.wikipedia.org/wiki/Qantas_Flight_30

[DogsEarsUp]

As Cabin Crew, we were always told that Chem-Ox generators couldn't be turned off (and were hot) and lasted 12 - 20 minutes. The 747-400 O2 system could be turned off and then re-used later (unoccupied seats) and lasted 20 minutes +. You need all that and more if you are over high ground and following an escape route. Worth remembering that not all compressions are rapid/catastrophic involving structural damage - some can be quite (relatively) slow in onset and down the back, you won't notice until your ears start going and you're farting like a good 'un.

[John H Watson]

. Where are the passenger oxygen tanks?

They are located in the (right hand) sidewall and ceiling of the forward lower cargo area, as are the crew bottles. The service ports are located just inside the door. Bottle numbers vary from aircraft to aircraft.

[John H Watson]

On the ER, most of the bottles were in the cargo ceiling (because of the Auxilliary fuel tank taking up room in the rear of the forward cargo).