We report a systematic study of the isothermal decomposition of ammonia borane, NH3BH3, at 363 K as a function of argon pressure ranging between 50 and 1040 mbar using thermogravimetry and differential thermal analysis Coupled with mass analysis of the volatile species During thermal aging at 363 K, evolution of hydrogen, aminoborane and borazine is monitored, with the relative mass loss strongly depending on the pressure in the react ion chamber. Furthermore, I lie induction period required for hydrogen release at 363 K decreases with decreasing pressure (C) 2009 Elsevier B V. All rights reserved.