Aluminium (Al) nanopowder has been shown to possess unique thermal behaviour and to enhance the performance of some energetic materials (EM). However,Al nanopowder has a high reactivity with water,which causes "aging" of Al nanopowder,and consequent reduction in its effectiveness in EM compositions. Water adsorption and desorption is a particular concern,since the aging reaction of Al nanopowders may be related to the water adsorbed on its surface. The thermodesorption of adsorbed gases on nanometer-sized aluminium powders was investigated using Thermogravimetry (TG) and Thermogravimetry-Fourier Transform Infrared-Mass Spectrometry (TG-FTIR-MS). The results show that the Al nanopowder studied contains 12 mass % of adsorbed gases. Desorption of water and carbon dioxide was observed by FTIR and MS. The kinetic parameters for the desorption of the adsorbed gases were determined using variable heating rate and isothermal studies. The activation energies of desorption obtained from the various methods are compared.