Techniques are described for determining the identity and toxicity of the pyrolysis products of plastics. Differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) determine the temperature at which the plastic melts, the temperature at which it goes through physical and/or chemical change (oxidation or reduction), and the temperature at which it undergoes weight losses. The identity and quantity of the combustion products are determined with a controlled combustion furnace, utilizing the temperature information obtained by DTA and TGA. The combustion products emitted by the furnace are separated by gas chromatographic techniques and analyzed by infrared absorption, ultraviolet absorption other gas chromatographic techniques, and mass spectroscopy. The results obtained utilizing polyvinyl chloride are described.