A soot formation and oxidation model appropriate for fires is first developed for laminar axisymmetric nonpremixed flames. This model relies on flow similarity relationships to describe the structure of the flame and relate it to soot processes in laminar smoke point flames. The selection of the parameters is focused on the stoichiometric and visible heights. The evaluation of this model is achieved by means of comparisons of numerical results with experimental data and observations for an axisymmetric coflow laminar ethylene/air nonpremixed flame. The model gives satisfactory results and a good phenomenological explanation of the influence of soot processes on the structure of the flame. This model will be applied next to turbulent flames and fires.