Occupational safety rules require the use of a hard hat in any situation where there is a potential for falling objects or other head injuries.
The University of Iowa explains that proper protection from a hard hat only happens when you wear it correctly and keep it in good condition. You should always throw out a damaged hat. The type of protection a hard hat offers depends on which type and/or class of hat it is.
A type 1 hat shields your head from blows to the top of the head. For example, it would protect you from a falling piece of debris that strikes the top of the hat.
Type 2 protection is for the top and sides of the head. It will defend against anything falling from above and collisions with objects.
This type of hard hat guards you against electrical shocks and burn for voltages up to 20,000. It also provides coverage for impacts to the top of your head. Do note the hat will only keep you safe if the contact of an electrical wire is to your hat. It cannot provide for your safety if you contact an electrical current with another part of your body.
A class G piece of safety gear provides top impact protection and guards against electrical shocks for low voltages. It can defend you from up to 2,200 volts.
Hard hats in this category defend only from impacts to the hat. They do not have electrical resistance. However, by design, they are lightweight and more comfortable to wear than those in other classes.