Carpet and carpet padding are frequently submitted to laboratories for
the analysis of residual accelerant in suspect arson cases. Charring
and pyrolysis of the above matrixes produces volatiles that can cause
interferences with some accelerants, most notably gasoline. A study wa
s conducted to evaluate the interference potential of pyrolysis produc
ts obtained from simulated fire debris samples and from samples collec
ted in the field. It was found that variable amounts of alkylbenzenes
and naphthalenes are produced, along with large quantities of styrene
and alkylstyrenes. Small amounts of higher-molecular-mass aromatic hyd
rocarbons are also generated but no alkanes or alkenes appeared. Since
aromatic hydrocarbons are the major diagnostic components in gasoline
, a potential interference is indicated. Careful observation of patter
ns within each group of isomers is required to rule out interferences.
The distribution of alkylbenzenes in gasoline is quite different from
the patterns produced by pyrolysis. Guidelines are proposed to distin
guish between petroleum-based aromatic hydrocarbons and those derived
from the pyrolysis of carpet/carpet padding. Mass fragmentography was
found to be particularly useful toward the discrimination of interfere
nces.