Final answer:
Small liquid oxygen cylinders are most often used in welding and metal fabrication, where oxygen serves as an oxidizing agent necessary for various processes including the use of oxyhydrogen and oxyacetylene torches.
Step-by-step explanation:
Small liquid oxygen cylinders are typically used in welding and metal fabrication. Oxygen is essential in this field because it acts as an oxidizing agent for various applications, including oxyhydrogen and oxyacetylene torches, which produce very hot flames required for the cutting, welding, and joining of metals. Large quantities of pure oxygen are also necessary in the steel industry, where oxygen is used to remove carbon from iron during steel production. While oxygen cylinders can be used for medical purposes and are indeed crucial in healthcare for aiding patients with breathing difficulties, the context provided suggests that the use within industrial processes, particularly metalwork, is pertinent.