Hydrogen is a very promising alternative fuel which is expected to play a significant role in the near future. Nowadays, hydrogen is considered as an excellent alternative fuel due to its potential to lead to significant reductions in greenhouses gas emissions and significant improvements in energy efficiency. On the other hand, significant issues are associated with hydrogen. A possible ignition may give rise to slow or fast deflagrations or even detonations under certain condition depending on the concentration, the size of the mixture and the geometry involved. In this paper CFD modeling techniques are used to simulate deflagration in homogenous, near stoichiometric hydrogen air mixture in a model of a tunnel. Because of the very confined space, a fire in a tunnel has always had much more serious consequences compared to open air fires. Therefore, it is crucial to establish possible fire scenarios and fire dynamic data in tunnels. Various simulations are conducted by modifying the boundary conditions. Specifically, the analysis focuses on how varying the inlet and outlet temperatures, as well as the hydrogen mass fraction, affects the combustion process. The results are analyzed and compared based on temperature, velocity, pressure, and density graphs. The acceleration of a flame and its detonation has a wide range of applications in industrial safety. Thus, the present study is to understand the mechanism of a flame’s acceleration, propagation and Deflagration-to-Detonation Transition (DDT) process. The computational work is carried out to calculate the run up distance from the region of ignition to the region of detonation and the DDT process was captured for the given time.