The behaviour of plastics, namely, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide and some copolymers, was studied in a combustion chamber in which the conditions of large-scale fires were simulated. Volatile combustion products were frozen-out or analyzed directly on two columns, one packed with Porapak Q and the other capillary column coated with squalane or CP Sil 5 CB. Carbonyl compounds were determined as the 2,4-dinitro-phenyl hydrazones on an OV-101 stationary phase. Thermal conductivity and flame ionization detectors were used. The decomposition products were identified either on the basis of retention data (retention indices) or by combined capillary GC-MS. The data obtained are used for the cataloguing of plastics from the point of view of their product toxicity during fires.