Re: A/C on fire

Date:         20 Nov 98 02:30:36 
From:         westin*nospam@graphics.cornell.edu (Stephen H. Westin)
Organization: Program of Computer Graphics -- Cornell University
References:   1 2
Next article
View raw article
  or MIME structure

jrp59@gte.net (Ron Parsons) writes:
> In article <airliners.1998.1722@ohare.Chicago.COM>, "Richard Rea" <rrea@xmission.com> wrote:

<snip>

> For what it's worth, aircraft are constructed of two main ingredients,
> aluminum and PVC (polyvinylchloride).

Not quite. Make that "metal and synthetic polymers" and you're a lot
closer. Cedeing the point that most of the metal would be aluminum,
there are lots of different polymers used. The seat cushions are
probably urethane, with rayon, nylon, or acrylic covers. The wall and
ceiling panels are probably fiber-reinforced polyester. I can't think,
off the top of my head, of any significant parts that would be made of
PVC.

> When PVC burns, it gives off
> chlorine gas, which was one of the gases banned for further warfare use
> after WWI.

I believe it's actually phosgene, which was used in WW I.

> Flight crews are provided with smoke hoods these days and they are even
> available commercially for individuals, but so far not required equipment
> for passengers.

I suspect that's because there are doubts about the efficacy of these
devices even for the flight crews; the ValuJet crash investigation
raised serious doubts that the smoke goggles in the cockpit would
really be usable in a real emergency, even by a trained flight crew.

Not to mention the cost and weight vs. the frequency of fire-caused
fatalities other than in fire-caused crashes.

> The smell you are familiar with as electrical smoke, is overheated PVC
> used as insulation on the wiring.

I believe aircraft use other materials for wiring insulation: PTFE for
one.

> Virtually the entire cabin interior is
> constructed from PVC materials.

Nope. Don't believe it. If you have vinyl upholstery in your car,
that's PVC. Chances are that the instrument panel is covered in ABS,
though, and various other plastics (polypropylene comes to mind) are
used elsewhere in visible interior components.

If your point is that synthetic polymers tend to emit toxic gases when
they burn, that's quite true. I believe research continues on safer
alternate materials, but I think that preventing and extinguishing the
fire itself has a higher priority in current safety thinking.

--
-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.