Abstract: An improved ventilation assembly for preventing fire and smoke from undermining a fire rated surface. The ventilation assembly includes a housing having at least one side wall defining an interior space, and a top wall coupled to the side wall, with an inlet adjacent the at least one side wall and an outlet coupled to the housing. A fluid, such as air, flows between the inlet and the outlet. A fire shielding material is disposed within the interior space, where the fire shielding material expands upon the application of a predetermined amount of heat such that the fire shielding material obstructs the flow of the fluid between the inlet and the outlet.