The constantly growing energy needs of the world accompanied by the emphasis on environmental pollution control have driven us to look at the possibility of hydrogen as a potential source of energy for the future. However, there are serious self-ignition hazards associated with its use, which are not yet fully understood phenomena. The issue of spontaneous ignition of highly pressurized hydrogen release is an important safety concern and it is necessary to understand its mechanism in order to adopt adequate safety measures. This paper describes a numerical investigation of the flow physics of a high-pressure hydrogen gas released through a tube into the atmosphere. The formation of a strong shock wave ahead of the high-pressure hydrogen jet causes an increase in temperature of the ambient atmospheric air, thereby leading to the possibility of ignition of the hydrogen-air mixture formed at the contact surface. The analysis of the physical mechanism of shock propagation and associated temperature profiles of the flow field are presented. Parametric studies based on the numerical results of temperature profiles obtained for the various initial conditions of release pressure and tube length have been carried out to study their effects on this high-pressure hydrogen gas behaviour and how they would favour occurrence of spontaneous ignition.