In what situation is it mandatory to wear a helmet?

Wearing a helmet is mandatory when working in areas where there is a risk of falling objects. This safety measure is crucial because falling objects can pose significant hazards that can lead to serious injuries or even fatalities. Helmets are designed to protect the head from impact and reduce the risk of injury from falling debris, which is common in many construction and work sites.

In contrast, the other options may not consistently provide sufficient protection. While a supervisor's instruction may be necessary for specific tasks, relying solely on that guidance does not ensure safety in hazardous environments where head protection is universally required. Working indoors might not inherently present the same risks as outdoor environments where overhead hazards are prevalent. Lastly, while wearing helmets in construction zones is often seen as a standard precaution, it is not limited to these areas; any environment with potential for falling objects necessitates head protection. Therefore, understanding the necessity of safety gear in context is essential for maintaining safety on the job.