Abstract: A thermal gravimetric analyzer includes a reaction tube disposed within a heating element and including a sample container disposed therein. A reaction gas is introduced at a first end of the reaction tube and allowed to react with the sample, while a purge gas is introduced at a second, opposed end of the reaction tube to isolate a beam system, from which the sample and sample container are suspended, from the reaction gas. A Fourier transform infrared (FTIR) spectrometer as well as a mass spectrometer coupled to the reaction tube may be used to analyze the off-gas products of the reaction of the sample with the reaction gas. Sniffer tubes are used to provide off-gas samples to the two spectrometers, with each sniffer tube having a first inlet end disposed immediately adjacent the sample container and a second outlet end coupled to a sample inlet port of a respective spectrometer.