Final answer:
Ozone (O3) is the gas produced by ultraviolet radiation in the air during welding operations, forming from oxygen in an endothermic reaction.
Step-by-step explanation:
The gas that is produced by the ultraviolet radiation in the air in the vicinity of welding operations is ozone. Ozone, or O3, is an allotrope of oxygen and can form in the lower atmosphere when ultraviolet light from welding reacts with oxygen.
This reaction can occur with the presence of ultraviolet light and does not require sunlight, which is why welding operations can produce ozone. The formation of ozone is an endothermic reaction where energy from the ultraviolet light causes a reaction between oxygen molecules (O2) and oxygen atoms (O) to create ozone (O3).