FAO Scy11a, Crazyscot

[zotz]

------------------------------
Risks Digest 24.93
Date: Fri, 21 Dec 2007 21:24:51 -0600
From: Peter G Neumann Subject: Nitrogen Used To Fill Aircraft Oxygen Systems

Comments

[pseudomonas]

I thought that aircraft didn't carry oxygen but chemical oxygen generators, at least for the main masks-that-drop-down stuff; possibly they have other contexts for oxygen, like medical supplies.

[_nicolai_]

This varies between aircraft types, some use oxygen cylinders for the oxygen masks. If you need therapeutic oxygen (which I think is stored separately, in hand-carryable cylinders), I don't think one can substitute therapeutic nitrogen either.

Overall, who needs terrorists when we've got stupids?

[pseudomonas]

Ah, thanks for that.

The therapeutic oxygen was what I meant by medical. Either way, it'd be extremely bad news for anyone trying to breathe it.

[_nicolai_]

I could see airlines wanting to carry therapeutic oxygen for passengers with breathing problems and therapeutic (... from the crew point of view) nitrogen for really annoying passengers...

[scy11a]

Oxygen comes in bottles with oxygen connectors - therapuetic or not. Nitrogen comes in bottles with nitrogen connectors. They do not mate with oxygen connectors. So, in fact, you have to be quite clever or at least ingenious to fill an O2 tank with N2 or in fact anything other than oxygen.

[_nicolai_]

As noted in the article, the stupids concerned were quite ingenious enough to swap the nonworking (correct) connectors on the nitrogen cart with their working (incorrect) connectors from their previous oxygen cart.
Just weld the connectors on; the idiots will set fire to themselves trying to detach the oxygen connectors with welding kit and that'll solve the problem.

.. you still flying for that orange airline, or not? Still hoping to get on one of your flights and say hello.

[scy11a]

Oh yes indeedy.

[_nicolai_]

That's carrying in the sense of "in the hold". Having them installed is still OK, and some currently-produced aircraft use them, eg the A330.
Also, oxygen for the flight crew is supplied from cylinders. Supplying them with nitrogen instead could cause a safety hazard since most current safety procedures for smoke or fumes in the cabin begin with "pilots should immediately begin to use oxygen masks".

[zotz]

They may do, or some may do. I don't know the current situation, but according to this FAA page,

The carrying of oxygen generators on passenger aircraft was banned following an in-flight cargo fire and subsequent crash of a ValuJet DC-9 near Miami, Florida, on May 11, 1996. The probable cause of the accident was determined to be the inadvertent activation of one or more oxygen generators in the forward cargo compartment that resulted in an uncontrollable fire

This does not, of course, mean that the situation hasn't changed since, or that other kinds aren't now used.

[zotz]

Actually, it looks like that means carrying them as cargo is banned, rather than their installation.

[scy11a]

Yes, so if we drop the 'rubber jungle' then the plane is effectively grounded until we can get spares sent out by road or ship : ( (or, of course, we could fly it back unpressurised or without passengers which would be cheaper).

Crew have a big O2 bottle to ourselves, and cabin attendents have therapuetic / portable oxygen bottles, but in the first instance they just sit down and use spare masks from the drop-down passenger oxygen