Use Of Pax Ox During Smoke/fire.

[ALLOW]

Hello,

Just wondering what you your view on this is.
Lets just say your flying at FL240 and you get a smoke warning from cabin crew with alot of heat but no sign of fire. The pax are struggling to breath. We go on OX but do you drop the passenger OX. My airline gives no guidance and i have yet to ask, i well next week and reporback.
My view is you do not drop them as the ox will feed the potential fire, either way the ox is mixed with the ambiente air so its pointless,or are am i wrong??

I have asked many experienced pilots from other well established airlines and as with most things they all had varied opinions. This surely is a something that should be clear cut and a big discussion point during training.

Any replies much appreciated.

Regards Allow!

[Storminnorm]

Let's face it Allow, if it's bad enough for people to have
breathing problems, it's bad enough to drop the masks.
Any increase in the cabin O2 levels will be minimal, but,
if it's severe enough to cause them breathing problems,
you have to do what you can to prevent any deaths in the
cabin. And get the thing down somewhere ASAP.
If it's not that severe, don't drop the masks.

[tom775257]

At the airlines I have worked at we wouldn't drop the masks, no real point as they mix the O2 with ambient air. We would suggest passengers cover their mouth and nose with clothing to filter out particulates.

If the smoke is bad, we would start a descent and then start to try and solve the smoke problem; upon reaching FL100 we would use the smoke removal drill - open the outflow valve fully and open the ram air valve to clear the cabin out, while carrying out a diversion.

[ALLOW]

So 200 odd masks dropping and producing OX for 12 mins would cause no effect as regards feeding the fire. I suppose its going to be one of those gray areas in airmanship, entirely depends on the scenario.

[MD11forever]

A32X: The oxygen flow only starts when a passenger pulls the mask towards the seat. Then the generator starts. One generator for the row. Worst case: You've got in every row one person, then you get all the generators activated, and I suppose this will rise the O2 partial pressure in the cabin. But with full house?

FCOM:
Chemical generators produce the oxygen. Each generator feeds a group of 2, 3, or 4 masks.
...
The generation of oxygen begins when the passenger pulls the mask towards the passenger seat. The chemical reaction used for oxygen generation creates heat. Therefore, the smell of burning or smoke, and cabin temperature increase, may be associated with the normal operation of the oxygen generators.The mask receives pure oxygen under positive pressure for about 15 minutes, until the generator is exhausted.

Additional question: The FCOM does not state if the Oxygen gets mixed with ambient air or not. I think it gets mixed, but I'm unsure right now. Anybody knows?

[Wizofoz]

Chemical Oxygen Generators enrich ambient air with Oxygen- You need a 100%O2 closed-system (as you have in the cockpit) before it would do any good at keeping contaminated air out of the Pax lungs. They are much worse off with an oxy mask on, thus unable to use anything to fliter the air, than they would be holding a blanket or towel over their face.

I don't think the small amount of Oxygen released would be a factor in inreasing the risk of an uncontrollable fire, but there isn't any point finding out.

[john_tullamarine]

The FCOM does not state if the Oxygen gets mixed with ambient air or not

During your next emergency refresher, have a close look at a pax mask and figure out the airflow.

Adding to previous posts, while there are variations in detail design, the generic strategy is that the passenger is breathing from a (rebreather) bag into which the supplemental oxygen flow (via the tube from the oxygen supply), ambient air (either via holes or a simple valve arrangement), and expired air (from the lungs) are allowed to mix prior to the next breath. This is not a closed system, though, and there will be provision for the bulk of the expired air to pass to the outside of the bag.

So far as the smoke scenario is concerned, the bag is pretty useless and counterproductive. However, you can rip the bag off the hose, stick the hose up your nose and then cover your face with (preferably wet) clothing as a filter. For hoses which have an inline expiration check valve, the other option is to disconnect the hose from the valve (usually just a simple hose over spigot fit) and use the supply hose end up your nose .. this one depends how long the hose from the supply to the valve is.

[Self Loading Freight]

So far as the smoke scenario is concerned, the bag is pretty useless and counterproductive. However, you can rip the bag off the hose, stick the hose up your nose and then cover your face with (preferably wet) clothing as a filter. For hoses which have an inline expiration check valve, the other option is to disconnect the hose from the valve (usually just a simple hose over spigot fit) and use the supply hose end up your nose .. this one depends how long the hose from the supply to the valve is.

An interesting challenge for the seatback safety card cartoonists.

Outside the technical discussions, though, I'd be worried at doing anything to the cabin at a time like that, that the cabin crew wasn't prepared for. If it's not in company procedures for the flight deck, it won't be anywhere else. Dropping the masks would signal decompression to the cabin crew, and increase their workload at a bad time.

The passenger oxygen system isn't designed for this, it hasn't been tested for this, it's there for a completely different reason. Is that something to add to the mix at a time when there are probably enough unknowns to be getting on with?

R

[muduckace]

This is allready a deadly scenario, there us no absolute solution to ensure life of pax. The mentality is to give the pax their best short term solution while the crew tries to find the nearest airport to egress.