Which harmful gas is produced from intense UV radiation in the surrounding air?

The production of ozone occurs when intense ultraviolet (UV) radiation interacts with oxygen molecules in the atmosphere. This process begins when UV rays break apart diatomic oxygen (O₂) molecules into individual oxygen atoms. These free oxygen atoms can then collide with other O₂ molecules to form ozone (O₃).

Ozone is considered a harmful gas at ground level because it is a significant component of smog and can have adverse effects on human health, including respiratory issues and increased rates of asthma. It can also harm vegetation and ecosystems. In the context of welding, the exposure to intense UV radiation can contribute to the formation of ozone, particularly in enclosed spaces where the concentration can build up rapidly.

The other gases listed—carbon dioxide, methane, and nitrogen oxide—are produced through different processes and are not directly associated with the photochemical reactions caused by intense UV radiation in the surrounding air. Thus, ozone is the correct answer in this context.