Abstract: A barrier system for partitioning a space includes panels which interlock with each other to provide a barrier that is fire rated. The interlocking panels are assembled in the barrier in columns using a tongue and groove assembly and a panel lock using a strike and latch supported by the tongue member and groove member, respectively. Each panel includes a peripheral frame (that is shaped to provide the tongue and groove members), opposed steel side faces mounted to the peripheral frame, and an insulation block filling an interior space delimited by the peripheral frame and the opposed steel side faces. The insulation block includes a pair of insulating material layers that sandwich a radiant barrier layer. A floor module supports a bottom edge of the panel and an interface module supports a side/top edge of the panel. The floor/interface modules are configured with telescoping sections and are length trimmable.