When it comes to Risk Analysis and Fire Safety Engineering, guaranteeing the reliability and the similarity between analyzed data and reality are extremely important. Computational Fluid Dynamics techniques (CFD) have been largely utilized to replicate fire accidents, enabling the analysis of temperature profiles and the quantification of thermal radiation incidence at specific points of the fire zone. The work here presented uses the open-source CFD toolbox named OpenFOAM, through the use of the fireFoam solver, present in OpenFOAM, we elaborate a comparative study between the thermal radiation models P-1, simpler and computationally less demanding, and Discrete Ordinates, more complex and robust, evaluating processing time and results’ confiability. Comparing the results to experimental data, we could observe the model DO predicted better results. A link between the number of angles, processing time and results is also shown.