On a construction site workers are required to wear hard hats in order to prevent head injuries. Despite this safety precaution, construction workers are vulnerable to several types of serious head injuries, including concussions, traumatic brain injuries (TBI), and closed‑head injuries. Concussions are caused by a blow to the head and result in a temporary loss of awareness. While most people fully recover from concussions within a few hours to a few weeks, repeated concussions or a severe concussion may require surgery or cause problems with movement, learning, or speaking.