Battery packs are presented. The battery packs include a plurality of cell blocks, each cell block comprising a plurality of battery cells. The battery pack also includes a plenum chamber configured to fluidly couple each of the cell blocks to an exterior of the battery pack in response to a thermal event in the battery cell in a separate cell block. In some embodiments, at least one of the cell blocks is configured to be fluidly coupled to the plenum structure via a cell block vent.