The following essay on fire is simplified and naive.  Chemists will
cringe.

The combustion products of a fire depend upon the fuel and the
completeness of the combustion.  I'm going to consider only two fuels,
wood and PVC plastic, both of which are commonly found around the
house.

Wood is a "natural" plastic, and I think it's basically cellulose
in a co-polymer of xylene, styrene and a few more complicated benzene
("phenol") ring molecules.  There should also be small amounts of
salts (chlorides, chlorates, sulphates, nitrates).  Its worst
combustion products (during incomplete combustion) are thus probably
phenols, which are poisonous but not really corrosive. During complete
combustion the gaseous products should be mostly water and carbon
dioxide.

In either case, there should be only small amounts of the acids from
the salts.  Wood ash, however, contains potassium hydroxide (caustic
potash) and sodium hydroxide (caustic soda), both of which can corrode
metal.

PVC (polyvinylchloride) on the other hand does not have rings, but
it does have chlorine, much more than wood has, and can thus release
substantial amounts of HCl (hydrochloric acid) during combustion.
HCl will etch most metals, including stainless steel, but not usually
silver or gold.

Peter Neilson
Sanford NC