A hard hat protects an individual from head injuries by deflecting falling articles. Any area where objects might fall from above requires the use of a hard hat, according to the Occupational Safety and Health Administration (OSHA). Besides flying object protection, some hard hat protect workers from electrical shock. OSHA 1910.135 governs the regulations pertaining to head protection devices while recognizing the American National Standards Institute criteria outlined in ANSI/ISEA Z89.1-2009.

Class G

Class G hard hats--equivalent to the old Class A hard hat in previous versions of the standard--protect the worker from falling debris as well as electric shock. Jobs in areas of overhead electrical wiring, not exceeding 2,200 volts, use this classification of hard hat. Maintenance personnel in factories, construction workers in low-voltage areas, iron workers, welders and logging personnel wear this class of hard hat, which provides workers with penetration resistance and impact protection from falling objects when worn. Type I or Type II hard hats determine whether the impact protection comes from the top or the sides.

Class E

Class E hard hats--formerly the old Class B--provide the highest level of electrical shock protection. The hard hat has a maximum electrical shock protection up to 20,000 volts. Flying objects and penetration resistance figures into this class of hard hat. Primarily worn by power-line workers, the Class E hard hat also provides electrical burn protection. Employees working in high-voltage environments must wear this classification of hard hat. Again, a Class E hard hat comes in Type I or Type II designs.

Class C

Class C hard hats--no change from previous standard--provide the least amount of head protection to the workers. The hard hat protects the worker from lightweight falling debris, but has no electrical hazard protection. Customarily, the Class C allows very little head protection. Therefore, workers wear Class C hats where little chance of falling debris exists, and no electrical shock hazards are within the area. Residential carpenters, laborers, factory workers and other employees working in limited head injury areas wear this classification of hard hat.

Bump Hat

The Bump Hat is the last classification of hard hat OSHA lists. Designed for employees working in low head clearance areas, this class hard hat protects the employees from laceration caused by beams, pipes or any confined area with little head room. Electrical shock hazards or falling object protection is not part of the design of the bump hat, which are commonly worn in non-hazardous areas, such as sporting events, food processing centers, pest control workers and repair garages. The American National Standards Institutes does not approve this classification of hard hat.