In this thesis the Minimum Ignition Energy, in a hydrogen-air system, is studied by Direct Numerical Simulations (DNS) in a program called the Pencil Code. The heat source used to achieve ignition is modeled by a Gaussian temperature distribution. Three different geometries of the heat source are looked upon, one with spherical geometry in three dimensions, one with cylindrical geometry in two dimensions and the last in one dimension. The results show that the dimensionality of the heat source has a strong impact on ignition.In addition, a new simpler zero dimensional simulation method is proposed with the goal of replicating the results from the Pencil Code. This method needs less calculation power, and uses ignition delay time data together with the heat equation to simulate ignition. The model has proven itself useful since it reproduces the Pencil Code results very well.