This study deals with the mixed convection flow through a shallow horizontal vent linking two compartments (one over the other). Depending on the temperature difference of gas as well as the ventilation flow rate between the two compartments, the flow through the vent can be bi- or uni-directional. A literature survey highlights that three correlations are used in safety engineering to calculate these upward and downward mixed convection flow rates. Unfortunately, for the same conditions, these correlations give very different results and, to date, there is no common agreement in the scientific community to identify quantitatively the most accurate model. This study proposes a new assessment of these correlations based on new experimental data obtained from the laboratory facility as well from the industrial apparatus. In addition, an improvement of the best model is proposed which better reproduced the experimental results. © 2019 by ASME.