This article examines various uncertainties relating to calculation methods for the balcony spill plume. The approach of physical scale modeling is used in the analysis. Comparisons are made between experimental results and predictions made using these calculation methods. This work has demonstrated that the presence of a downstand from the soffit at the spill edge of a compartment opening appears to have little effect on the entrainment of air into the subsequent spill plume. A simplified spill plume formula has also been developed to predict the mass flow rate of gases, which inherently includes entrainment of air into the free ends