Many construction workers have the perception that you are only required to wear a hard hat when you have overhead hazards. This is correct, but it is definitely not the entire story. The criteria for wearing a hard hat includes; the possible danger of injury from impact, falling objects, flying objects, or from electrical shock or burns.
This is why most General Contractors require the entire job site to have hard hats worn at all times. A hazard assessment should be done to determine whether there is potential danger of head injury from any of the criteria listed above listed criteria. They type of work and the condition of the construction zone should be assessed critically.
The hard hat must be in good condition and meet the requirements for the type of possible exposure it will have in regards to the construction zone. There are always times when unusual occurrences happen and hard hats save lives. For that reason, hard hats should be worn. You never know when you might have needed one.