Re: What toxic fumes are created when PVC it heated enough to smoke (no fire)?

Pyrolysis (heating till smoke evolves) of PVC causes the  production of 
char and tar and the formation of chlorinated hydrocarbons, mainly 
chlorobenzene.  Incineration of PVC leads to the formation of chlorinated 
dibenzodioxines and dibenzofuranes in the flue gas.  Thermal degradation 
of PVC in an inert atmosphere produces HCl-gas, gaseous and liquid 
hydrocarbons, char and an inorganic solid residue, originating from 
additives. In a steam atmosphere at high temperatures the char fraction 
will not accumulate, like in pyrolysis, but will be converted to 
carbonmonoxide and hydrogen. The inorganic solids will be separated from 
the product gas, HCl can be recovered and the high caloric hydrocarbon 
residue can be used for energy recovery.

By virtue of its chlorine content, PVC has inherent flame retardant 
properties, and it is therefore unlikely that a spark from a welder's 
torch could ignite PVC cables for example. 

An interesting fact with regard to PVC products is the deterioration of 
old toys made of PVC such as Barbie dolls.  Old Barbie dolls sometimes 
develop green patches on their skin.  The culprit is not PVC but 
plasticizers added to it to make it flexible.  An interesting article can 
be found at http://www.natmus.dk/cons/lab/barbie/bb.htm.

In summary melting and subsequent evolution of smoke does result in toxic 
products being evolved.  IF you need info on the toxicity of the chemicals 
I had listed above you can look up what are called MSDS sheets on the web. 
MSDS stands for Materials Safety Data Sheets. Goto www.google.com and 
type “MSDS Sheets” in the search box.

Hope this helps.