With the improvement in mechanical and other properties of plastics, they are founding greater use in industries. we can use mechanical fastening, adhesive joining and welding for joining plastics. Generally plastics are classified as thermoset and thermoplastic. Since thermoset plastics can not be resoftened, they are joined by mechanical fastening and adhesive joining. But thermoplastics can be resoftened so they can be welded. One of the easiest and cheapest welding technique is Hot Gas welding technique. In 1940, Reinhardt patented the hot gas technique in which hot gas stream is used to increase the temperature of weld groove and welding rod, so that they become tacky. Then the welding rod is pressed onto the weld groove for joining.