Abstract: Ammonia gas is toxic and flammable and exposure to ammonia can cause eye irritation, headaches, and dyspnea in humans. There is a common misconception that the pungency of ammonia makes it easy to identify even the smallest leak and that its relatively high flammability limit allows for simple, quick safety measures to avoid fire or explosion. However, on February, 13, 2014, ammonia gas used as a refrigerant in a high-pressure gas refrigeration facility in Namyangju-si, Gyeonggi-do exploded. This accident resulted in significant academic and industrial interest in the hazards of ammonia gas explosions. Although, ammonia gas leaks do not typically reach the explosion limit concentration because it is lighter than air and thus easily dispersed, if the gas leaks into a confined or poorly ventilated space, the explosion limit can be easily attained and the presence of an ignition source can then result in an explosion. To determine the nature of the explosion hazard presented by ammonia gas, this study evaluated the behavior and explosion potential of an ammonia gas leak accounting for the leakage and dispersion conditions of the February, 2014 explosion. To determine the likely concentrations of gas, the overpressure blast waves resulting from the upper and lower limits of the explosion range were determined by PHAST Software simulation and compared to observed damage from the February, 2014 explosion. The overpressure resulting from the explosion of gas at the upper explosion limit, achieved as the concentration of gas was reduced into the explosion range during an attempt to vent the leaked ammonia gas was determined to have been capable of inflicting the observed damage, providing a general understanding of the process that led to the explosion and informing several proposals to mitigate the risk of ammonia explosions in the future.