Abstract: A self-contained heat recoverable exothermic chemical heater to provide heat to a recoverable sleeve. The heat recoverable heater provides superior thermal contact as the sleeve recovers and, in particular, after recovery when additional heat is required to melt an adhesive. A first and second heat bag, each having a different chemical means disposed in its separate compartments, are bonded together. The separate compartments maintain the correct proportions and proper distribution of the chemical means for optimum mixing. The rupturable barrier enclosing each of the compartments can be almost totally removed to allow the rapid and complete mixing of the chemical means without permitting any of the chemical means to escape. The removal of the rupturable barrier causes the chemical means to mix, thereby generating heat. The adhesive partitioning the heat bags into separate compartments releases its bond as a result of the increasing temperature.