Helmet

A helmet is a form of protective gear worn to shield the head from injury. Helmets are used in sports, work, military, and transportation to reduce the risk of traumatic brain injury and skull fractures. They function by absorbing and redistributing impact energy and by securing the head within a stable shell.

Most helmets consist of a hard outer shell and an energy-absorbing liner, plus a retention system and comfort padding. Outer shells are made from polycarbonate, ABS, fiberglass, carbon fiber, or composites; inner liners are often expanded polystyrene (EPS) foam or similar material. Some helmets also incorporate visors, face shields, or ventilation.

Safety standards and certifications vary by application and region. Motorcycle helmets in the United States typically conform to DOT or newer federal standards; in Europe, ECE 22.05 or 22.06 is common. Industrial hard hats are evaluated under ANSI/ISEA Z89.1 or EN 397. Sports helmets may meet standards from organizations such as Snell, ASTM, or CPSC.

Head protection is specialized for different activities. Cycling, motorcycle riding, horseback riding, skiing and snowboarding, and combat sports each have helmets designed to mitigate common impact directions and energy levels. Industrial helmets protect against falling objects, while military helmets may provide ballistic protection.

The helmet has a long history. Protective headgear traces to ancient civilizations. Modern designs emerged in the 19th and 20th centuries, with bicycle helmets popularized in the 1960s–70s and football and motorcycle helmets evolving through the late 20th century to improve impact performance.

Proper fit is essential: the helmet should sit level on the head, cover the forehead, and be secured by an adjustable strap. Helmets should be replaced after a significant impact or after the expiration date, and must be maintained clean to preserve materials.