Which of the following is NOT an ignition source during welding and cutting?

In the context of welding and cutting, an ignition source is anything that can produce enough heat or spark to ignite flammable materials. Hot work pieces, electric arcs, and gas flames are all capable of generating sufficient heat to ignite combustible substances present in the environment.

Hot work pieces refer to any items that have been heated through the welding or cutting process; their elevated temperature can ignite combustibles. Electric arcs, present in processes like arc welding, generate intense heat as electricity jumps between the electrode and the workpiece, making them a significant ignition source. Gas flames, commonly used in various cutting processes, also produce high temperatures that can easily ignite flammable materials when they come into contact.

In contrast, cold air does not generate heat and therefore cannot ignite materials. Since it does not possess the necessary thermal energy or attributes to serve as an ignition source, it stands out from the other options, making it the correct answer to the question. Understanding the characteristics of different ignition sources is critical for maintaining safety in welding and cutting operations, as it helps to mitigate fire hazards effectively.