Normally, thermoplastic materials are utilized as the raw material of 3D printers, while more advanced and sophisticated prototype uses the precursor of thermoset materials (or a prepreg) as the feedstock sources. Due to the reaction nature of the precursor, various toxic gases could be emitted during the printing procedure, including regulation prohibited chemicals. GC/MS is normally used for the identification of potentially harmful chemicals, though it does not necessarily provide the rough distribution of the evolved mixing gas debris. Moreover, extensive sample preparation is required. With Hyphenated techniques coupling TG and GC/MS, labs can benefit from minimized sample preparation while qualitatively study the gas evolved and the degradation components that can be identified to discern the polymer engineering. This application note reports the results of TG-GC/MS Analysis for the in-situ study of the chemical nature of evolved gases during the 3D printing performed with the PerkinElmer Hyphenation System with TG-GC/MS configuration.