This study demonstrated that the fire performance of materials cannot be expected to correlate in a small vertical flame test with the fire performance in other scenarios where conditions can be very different. However, in this study, an engineering analysis of the vertical Bunsen burner ignition test could provide a reasonable description of the ratings of plastics according to UL-94V test and a physical basis for this universal flammability test using known material fire response parameters such as critical heat flux, heat release parameters, and thermal response parameters, in combination with critical heat release rates for ignition, sustained burning, and upward flame spread.