The decomposition of uranium hydride powder was studied using thermal desorption spectroscopy (TDS). In the TDS spectra, three distinct decomposition peaks were observed. However, only the high temperature peak was associated with an activation energy, calculated to be 43 kJ/mol H. This activation energy was used to construct outgassing diagrams that can be used to estimate the temperature and time dependence of UH3 decomposition. Potential models for explaining the three decomposition peaks and, thus, the decomposition mechanism are also presented and compared with H desorption energies calculated from first principles. Additional experiments on α-U coupons containing UH3 corrosion pits were also performed. In those samples in excess of 6 peaks are observed. It is shown that the first three hydrogen peaks are related to the decomposition of UH3.