Abstract In order to ensure the responsible use of anhydrous ammonia as clean marine fuel, safety aspects in respect of its post-release consequence cannot be understated. This contribution is aimed to address the gaps of understanding associated to events of ammonia loss of containment (LoC) in enclosed spaces onboard ammonia-fuelled vessels. A forced ventilated fuel preparation room (FPR) onboard a container vessel is chosen as a study case with minor and major release scenarios, which is based on the orifice size. The dispersion analysis was performed using three-dimensional computational fluid dynamics. The analysis revealed that toxicity associated to the rapid and persistent ammonia vapor cloud buildup is by far the most significant hazard in the space. In the major release scenario, gradual evaporation of rainout pool increases the vapor cloud persistence even far beyond the leak isolation time. The results and finding above underlines the importance of concerted effort in mitigating not only the ammonia vapor cloud, but also the accumulated ammonia liquid pool.
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