<；p>；The invention discloses a method of manufacture of disposable heat packs. The heat packs contain an exothermic composition comprising of: (a) pre-soaked insulating and water retentive particulate material； (b) pre-soaked absorbent gelling material； (c) a metallic mixture. The metallic mixture comprises of at least one or more bivalent metals, metal halides, water- retentive substances, adsorbing substrate and optionally additives. The gelling material is added to the particulate material to form a homogenous mixture , to which the metallic mixture is added； and the exothermic composition is then filled in to the packs, so as to enable giving sustained heat release for 4 to 25 hours at a temperature range of 40°-75 °C on exposure to air.<；/p>；
