horizontal sealing bar seals the top of the bag, simultaneously forming the bottom of the next bag above. This bag is then cut off from the tube and is now a sealed package, ready to advance onward into the product boxing and shipping processes. During the final sealing process, the bag may be filled with air from a blower or from an inert gas supply such as nitrogen. Inflating the bag helps reduce the crushing of fragile products such as potato chips, while inflating with inert gas helps drive out oxygen and retards the growth of bacteria that would spoil the product. Other product finishes such as hole punching for retail hanging racks will be done concurrently or just after the "Top Seal" is made. The feeding of material and cutting of the bag/pouch can be determined either by pouch length, or by indexing to an eyespot (photo registration mark), which is detected by a visual sensor. While single web systems are popular for food applications, the dual web four side seal system is often popular for IVD and Medical device products. Closely related is the horizontal form-fill-seal machine, which generally uses more floor space than a vertical system. Modern advancements in pouch forming technology have allowed for smaller and smaller Vertical pouch forming systems. Many food filled packages are filled with nitrogen to extend shelf life. Food manufacturers are often looking for ways to improve their geographical reach or otherwise extending the shelf life of their product without the use of chemicals. Nitrogen filling is a natural means of extending shelf life. More and more manufacturers are choosing to create and control their own nitrogen supply by using an on demand nitrogen generators. Dual web systems Dual web systems are also available for four side sealed pouches, as well as pouches requiring different materials for each side. Dual web systems use two rolls of material instead of one, which are fed in from opposite sides of the machine. The bottom and sides are heated sealed together to form the pouch, and the product is loaded from the top. The pouch with the loaded product then advances downwards; the top is sealed and the pouch is cut off. The sealing of the top of the pouch forms the bottom of the next pouch. During this process a tear notch may be added. See also Filler (packaging) Food packaging References Industrial