The use of lithium-ion battery energy storage systems at the grid scale has increased significantly in recent years. These systems can make the grid more robust or more efficient and can enable the use of stored energy from renewable sources. To achieve optimum performance and lifetime from lithium-ion cells, the cells must be maintained within their temperature specifications. Typical grid scale battery energy storage systems, therefore, are equipped with dedicated HVAC systems. In many cases, these HVAC systems are built into a “containerized solution,” where standard shipping containers house all of the components necessary for operation and also connection to the grid (i.e., racks of lithium-ion batteries, HVAC equipment, battery management systems, power electronics, etc.). The enclosed space that contains the lithium-ion batteries presents unique hazard considerations for the HVAC design engineer. During thermal runaway failure, lithium-ion batteries release a substantial volume of flammable gases (e.g., hydrogen, carbon monoxide, methane), and they also release substantial heat (which can serve as an ignition source). These characteristics present a potential explosion hazard, and the HVAC designer should be aware of the implications of how the HVAC system functions under alarm conditions, how gases mix in the space, influence of ventilation (introduction of air from the outdoors into a building), the consequences of an explosion in the system, the limitations of various fire protection systems, and other considerations. This paper outlines how an explosion hazard may develop in a containerized lithium-ion battery system and discusses various possibilities for mitigation, including in the context of NPFA 68 and 69, which address explosion hazards.