h a l f b a k e r y
Clearly this is a metaphor for something.
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Most commercial flights cruise for extended periods at almost
double the height of Mt Everest where the air pressure is very
low. Aircraft are designed with pressurization systems that
increase the internal pressure* to compensate for this so that
people continue to live.
the aircraft fuselage into something
approximating a flying aluminum** balloon. Balloons pop, e.g.
a window falls out <link> or deflate if someone forgets to seal
<link>. In this situation, the humans on board will experience
rapidly declining cognitive function before falling
possibly permanently. You have something like 10-30s of
consciousness depending on the altitude situation.
The conventional solution to this is to fit passenger transport
aircraft with an emergency oxygen system, usually stored in
panels above each seat. These systems usually use a chemical
reaction to generate oxygen for long enough, approx. 10-30
mins. in this time, the pilots should have initiated an
automatic*** descent to ~10,000ft or so where everyone
be OK to breath... but, oh no! the depressurization was
by a fire started in a poorly labelled shipment of lithium
batteries**** in the cargo hold! The fire suppression systems
work through displacing oxygen, and lithium batteries don't
about that. The hole in the side allows the CO2 to escape and
now other things ignite.
The pilots have diverted and are now on approach to a closer
airfield, but acrid burning plastic fumes begin to fill the
the oxygen masks do not seal and chemicals in the plastic
smoke (ironically, many of them chosen because they do not
burn) are horrific irritants to the lungs and eyes. Despite the
fact the aircraft makes it to the ground in one piece, the
and panic kill many.
So, the solution to this is to replace the oxygen mask with a
smoke hood<link>. These are hoods that go over the head, as
hoods are wont to do, and are equipped with a similar oxygen
generating system + CO2 absorber, this inflates the hood and
prevents acrid smoke from being inhaled/reaching the eyes.
Same advantages in a decompression scenario but with the
benefit of being useful in a fire.
*but not humidity
**or plastic, for the 787 fans.
*** in case they pass out too
**** Another one for the 787 fans.
Windscreen blow out BA5390
[bs0u0155, Nov 11 2021]
Aircraft pressure leak Helios 552
[bs0u0155, Nov 11 2021]
[bs0u0155, Nov 11 2021]
Smoke Clearance 737
[bs0u0155, Nov 19 2021]
THE SMOKE HOOD: A LIFESAVER?
(from 1993): For about two decades, the world's airlines have been studying the possibility of installing passenger smoke hoods in planes, but for several reasons -- among them, the possibility that hoods might actually delay emergency evacuation -- they have declined to so. [a1, Nov 19 2021]
Smoke Hoods are now routinely provided for Cabin Crew but, despite years of debate dating back to as long ago as an NPRM (Notice of Proposed Rule Making) issued by the FAA in 1969, they have not yet been approved for passenger use. [a1, Nov 19 2021]
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||I cant tell you if it applies to all jets but if smoke
becomes the #1 threat there IS a smoke clearing
procedure that involves depressurizing the plane
and ventilating the cabin with ram air, in which
case the regular oxygen masks may be useful.
||People under stress/panic heavy breathe. A hood isn't going to fog up, is it? Desiccant possibly.
||//if smoke becomes the #1 threat there IS a smoke clearing
procedure that involves depressurizing the plane and
ventilating the cabin with ram air,//
||I can't find an awful lot on this in a brief google, I suspect
it's very aircraft type specific. Does, say, a 737 have a ram-
air intake? I mean I know they do, but as far as I can tell,
these are intakes for bleed air cooling and aren't linked to
the cabin. A read through this <link> (pg9) suggests there is
high flow for smoke clearance, but it's all from the
||And none of this helps you much on the ground.
||//A hood isn't going to fog up, is it?//
||There's a few things working in our favor. 1, if the mask
type is an O2 generating model, then the O2 generation
puts out completely dry O2. The CO2 absorbtion system, be
it NaOH/CaOH or LiOH are all incredibly hygroscopic and
absorb water vapor readily.
||The activated carbon types, typically have mouth pieces so
that the breath doesn't get into the same space as the eye
||I think we're OK on this.
||[-] not a new idea - and despite decades of
rarely if ever implemented anywhere. See linked
article from 1993 and Skybrary article from 2030.
||Is there a psychological barrier?. Hey, really scared person put this bag over your head. You will feel better,trust me.
||So perhaps an oxy mask/goggles combo - of course, as a scuba diver / motorcycle helmet wearer, my opinion is valueless ...