This specification describes the performance and design of self-contained heater modules consisting of polymeric food trays, Institutional Size Pouches (ISP) or Boil-In-Bag (BIB) modules, flameless heaters, activation fluid, heating trays, an activation mechanism and other components, as applicable. The heater module is used by the Department of Defense as a component of the Unitized Group Ration-Express㢠(UGR-Eã¢) operational group ration to provide hot meals to eighteen individuals.