Electrolysis experiments were conducted in a sealed laboratory scale furnace with inert gas purging. Anodes of different industrial qualities, as well as a graphite anode, were studied at different potentials and current densities from open circuit to the onset of PerFluoroCarbon (PFC) evolution. Utilizing Mass Spectrometry (MS) and Fourier Transform InfraRed Spectroscopy (FTIR) the off-gas composition for the different anodes were continuously monitored. The off-gas compositions recorded were compared as function of the applied cell voltage. The release of different sulfur species were particularly interesting, as the production of these seemed to decrease over time, and did not appear to be related to the current density, or applied voltage, in the same way as the CO/CO2 production did. Differences in the onset potential for perfluorocarbon gases were compared for the different anode types in order to investigate whether anode morphology and impurity levels affects the onset of PFC.