The main type of personal protective equipment used to prevent head injuries is a _______.

The correct answer is the protective helmet, which is designed specifically to safeguard the head from a variety of potential hazards. This includes risks from falling objects, bumps, and electrical hazards, all of which can cause serious head injuries. Protective helmets are crucial in environments where heavy equipment is present or where there is a risk of impact, such as in construction, manufacturing, or other industrial settings.

While hard hats serve a similar purpose and are indeed one type of protective helmet, the term "protective helmet" encompasses a broader range of protective headgear that may include variations designed to address specific risks.

Face shields and safety goggles, although important in their own right for protecting the face and eyes from impacts or chemical splashes, do not provide the same level of protection to the head as a protective helmet. Thus, when considering the main type of personal protective equipment specifically intended to prevent head injuries, the most comprehensive and accurate term is protective helmet.