Lithium-Ion Battery Energy Storage Systems (BESS) are required to obtain approval from the New York City Department of Buildings (NYCDOB) Office of Technical Certification and Research (OTCR) and the New York City Fire Department (FDNY). This BESS is located on a Rooftop in close proximity to three buildings and was determined to be an exposure hazard due to deflagration vents on the top of the BESS container. Sparc prepared a performance-based design analysis and utilized computational fluid dynamics modeling (CFD) to determine the potential effects of a fire emanating from the deflagration vents. Sparc’s analysis determined that the established performance criteria of the adjacent buildings’ materials were not exceeded and the NYCDOB and FDNY accepted the proposed location of the BESS container.