Ask A Scientist© Chemistry Archive

name       Dave
status       student
age          30s

Question -   Hi
I am studying a fire management course. My question to you is: What are
the toxicology effects of burning
Poly Vinyl Chloride (PVC). Am I correct in assuming that hydrogen Chloride
(HCL) is the primary fire gas as well as Carbon Monoxide and
Carbon Dioxide. Is the sheathing surrounding electrical cables PVC?
--------------------
Dave,

Am I correct in assuming that hydrogen Chloride (HCl) is the primary fire gas
as well as Carbon Monoxide and Carbon Dioxide. ---- Yes. As you know, HCl 
(gas)
is quite soluble in water. A mist will effectively knock it down.

Is the sheathing surrounding electrical cables PVC? ---- Yes

In general, the combustion products of plastics are very complex. Their
identity depends on other substances that can act as a catalyst in their
degradation, the oxygen content in the air and other oxygen bearing chemical
substances which may be present, and, of course, reaction temperature. It is
always wise to wear proper respiration equipment when battling fires fed by
plastics and asphalt (hydrocarbon based) materials.

Regards,
ProfHoff 313
========================================================
Wire manufacturers still seek the perfect cable-protecting coatings, but my
understanding is that PVC-type coatings are what they currently use most
often.
In the ideal world where all reactions go in the desired direction with 100%
conversion of reactants to products, you would see hydrogen chloride and
carbon dioxide from the decomposition of pvc.  In the real world, where
carbon monoxide is anticipated, we also would probably get some vinyl
chloride and vinylidene chloride (the "hot electronics/wiring" smell).  Also
a likelihood of phosgene. These chloride gases are likely created and
emitted by the heat decomposition of PVC but may escape before their own
combustion.  In referring to primary fire gases, do you mean in terms of
relative abundance, or relative hazard?  You can find pertinent data (such
as reaction products anticipated, toxicological effects, etc.) in texts such
as:
Hazardous Chemicals Desk Reference (Richard J. Lewis, Sr.) John Wiley &
Sons, Inc., or
Sax's Dangerous Properties of Industrial Materials (same editor/publisher)
or any of several others that are available.
Tim Spry
========================================================
Hi, Dave !!

Yes, you are right!!! The burning of PVC
produces Hydrogen Chloride (HCl)
in form of gas in the smoke, as well as Carbon Monoxyde and also
dioxins and chlorinated furans that, in turn,
are powerful cancer-causing substances. When inhaled - as you know -
HCl forms Hydrochloric Ácid (HCl + H20          ( H30)+   +  Cl-  )
once absorved in the lungs and can cause fluid build up and
ulceration of the respiratory tract.

The sheathing surrouding electrical cables are really made up
of PVC what causes an additional problem in cases of fire.
Some years ago, an airplane left Brazil to land in Paris. There
was a fire and most of the people died as consequences of gases
from PVC and not because of the fire itself. A famous brazilian
singer died there. The airplane could land in the Charles de Gaulle
airport, but people were already dead because of the smoke.
Some people that used a umid cloth to breath through could
scape alive from this tragic flight.

Alcir Grohmann
Beschaffung SAM
========================================================
The combustion products you mention are the major ones. Yes, some
electrical cables are insulated by plasticized PVC. The following website
gives detailed info on the combustion of PVC.
http://www.vinylsiding.org/vsic/publications/fire.htm

Vince Calder
========================================================
I do not know for sure about electrical insulation, but I could believe that
PVC is used.

If the combustion is complete, yes, PVC will produce hydrogen chloride gas.
However, with less complete (smoky) combustion, a host of other
chloringe-containing compounds will be produced.  One of the more
politically troublesome, although it is formed in small amounts, is TCDD,
commonly known as "dioxin", and its relatives.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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