Two types of polytetrafluorethylene, Teflon-1 and Teflon-6, and polyfluorethylenepropylene, Teflon-100, were studied in this investigation. Each type was placed in a furnace operating at temperatures of 350, 490, 565, 670, 760, and 875 degrees C and the decomposition products formed were analyzed with a time-of-flight mass spectrometer. The atmospheres used in this study included air, oxygen, and nitrogen. The effect of varied amounts of moisture in air on the nature of the decomposition products was also investigated. The decomposition products formed at each temperature with the specific atmospheres and humidities were identified.