The exchange of warm and Cold air masses through doorways due to natural convection is a well-known phenomenon observed in the operation of cold storage rooms. This process results in an increase in refrigeration load for these facilities as a resultof sensible and latent heat entering with the warm air; the problem has been studied to some extent by previous researchers, but analytical models developed to predict doorway infiltration heat gain still lack adequate verification. The primary objectives of this research project were to develop a better understanding of the natural convection process and to determine the predictive ability of existing analytical models. This study was accomplished through field experimental measurements made on full-size, working cold storage rooms, A preliminary investigation of doorway infiltration protection equipment was also conducted.