A hard hat is a type of helmet predominantly used in workplace environments, such as construction sites, to protect the head from injury by falling objects, impact with other objects, debris, bad weather and electric shock. Inside the helmet is a suspension that spreads the helmet's weight over the top of the head. It also provides a space of approximately 30 mm (1.2 inch) between the helmet's shell and the wearer's head so that if an object strikes the shell, the impact is less likely to be transmitted directly to the skull. Sometimes the helmet shell has a midline reinforcement ridge, which strengthens it against impact. Source: Hard hat.