A two-way pressure relief assembly for a plenum chamber including, at least two ported valve seats communicating with an outlet of the plenum chamber, and a plurality of relief valves adapted to respond to fluid pressure surges of a preselected magnitude, one valve cooperating with each ported valve seat, with at least one of the valves being responsive to fluid pressure surges of a preselected magnitude in a direction counter to the direction of fluid pressure surges to which the remainder are responsive.
