A thermogravimetric analyser was coupled to a Fourier transform infrared and a mass spectrometer in parallel to form a TGA - coupled - FTIR/MS system. This has been optimised to enable quantitative determination of the volatiles released from samples under investigation. The system itself and the modifications necessary to perform quantitative determinations are described in this contribution. Calibration experiments indicate that the present system is able to determine quantiatively polar and non-polar components with boiling points up to about 250 degrees C. For polymer research, the TGA - coupled - FTIR/MS system is especially suited to determine residual solvent, residual monomer and the released components in the earliest stage of a thermal degradation process.