Which of the following conditions are not acceptable for a hard hat?

A hard hat is designed to provide protection for the head against impact and penetration from falling or flying objects, as well as protection from electrical hazards. The integrity of the hard hat is crucial, as any modifications or defects can compromise its safety features.

The correct answer highlights that a metal shell with holes drilled in it is not acceptable. Drilling holes into the helmet's shell can significantly weaken its structure, reducing its ability to absorb impact. The creation of holes can also potentially expose the wearer to electrical hazards, as the effectiveness of insulation may be diminished. Therefore, it is essential that hard hats maintain their structural integrity, and any modification that introduces weaknesses would render them unsafe for protective use.

On the other hand, a metal shell with suspension and a shell made of plastic, both of which are acceptable designs, are engineered to meet safety standards and provide necessary protection without compromise. Furthermore, leaving no holes drilled in the shell confirms the importance of maintaining the hard hat's protective capabilities.