The mechanisms of transfer of sulfur to the volatile phase and char phase during the pyrolysis of tires have been investigated by complementing the available literature data with TGA experiments. For isothermal experiments, the global selectivity expression could be simplified into an intrinsic form of sulfur loss selectivity, which is solely a function of temperature. Two other phenomena have been found to influence the intrinsic sulfur loss selectivity: solid matrix desulfurization and metals sulfidation. In the case where tires would contain no metals and pyrolysis was performed at a temperature of 400 degrees C or higher, decomposition kinetics is limiting and the intrinsic sulfur loss selectivity would converge to the value of 1. Below 350 degrees C, mass transfer limitation will promote solid matrix desulfurization, producing sulfur loss selectivity greater than 1. Over 350 degrees C, if zinc and/or steel are present in tires, sulfidation will cluster sulfur in the solid phase and sulfur loss selectivity will become lower than 1. A developed form of sulfur loss selectivity could be obtained to account for these phenomena.