A helmet is a form of protective gear worn on the head. Traditionally, helmets have been made of metal. In recent decades helmets made from resin or plastic and typically reinforced with Aramid fiber (e.g. Twaron or Kevlar) have become preferred for most applications. Designed for protection of the head in combat, or in civilian life, from sports injuries, falling objects or high-speed collisions.

Helmets are common in the military, construction, mining, and some sports, including American football, baseball,, ski, snowboarding, ice hockey, equestrian sports, motorsports, and rock climbing. Motorcycle helmets and bicycle helmets are compulsory headgear in some jurisdictions; in the United Kingdom only Sikhs are allowed to ride motorcycles without wearing motorcycle helmets. Bicycle helmet compulsion and even strong promotion has been a heated subject of debate amongst cyclists and scientists since at least the 1990s, lately focusing on alleged net protective effect at the population level.

Military origins and symbolism

Main article: Combat helmet

Helmets were among the oldest forms of combat protection, and are known to have been worn by ancient Greeks, Romans, throughout the Middle Ages, and up to the end of the 1600s by many combatants. At that time, they were purely military equipment, protecting the head from cutting blows with swords, flying arrows, and low-velocity musketry. Some helmets, in order to protect the neck as well, have a sort of extension made of leather strips called pteruges, particularilly common in the middle east. They were initially constructed from leather, and then bronze and iron during the Bronze and Iron Ages, but soon came to be made entirely from forged steel in many societies after about 950A.D. Military use of helmets declined after 1670, and rifled firearms ended their use by foot soldiers after 1700. By the 18th century, cavalry units often wore steel body cuirasses, and frequently metal skull protectors under their hats, called "secrets". The Prussian spiked helmet, or Pickelhaube, offered almost no protection from the increased use of heavy artillery during World War I, and in 1916 was replaced by the German steel helmet, or Stahlhelm, and afterwards it was worn merely for tradition.

The Napoleonic era saw ornate cavalry helmets reintroduced for cuirassiers and dragoons in some armies; they continued to be used by French forces during World War I as late as 1915, when they were replaced by the new French Adrian helmet. It was soon followed by the adoption of similar steel helmets by the other warring nations.

World War I and its increased use of heavy artillery had renewed the need for steel helmets, which were quickly introduced by all the combatant nations for their foot soldiers. In the 20th century, such helmets offered protection for the head from shrapnel and spent, or glancing, bullets.

The use of protective helmets by millions of fighting men in the two world wars increased awareness of "hard hat" protection. By the 1950s, hundreds of new applications for helmets were found. The helmet offered an unexpected advantage: Symbolism. It can signify that, like a soldier, the wearer is someone qualified for or capable of a certain task or activity, such as construction, operation of heavy machinery, or participation in certain sports.

Today's militaries often use high-quality helmets made of ballistic materials such as Kevlar, which have excellent bullet and fragmentation stopping power. Some helmets also have good non-ballistic protective qualities, though many do not. Non-ballistic injuries may be caused by many things, including (but not limited to) concussive shockwaves from explosions, motor vehicle accidents, or falls.

Function and structure

Despite various designs and requirements, helmets attempt to protect the user's head through a mechanical energy-absorption process. Therefore, their structure and protective capacity are altered in high-energy impacts. Beside their energy-absorption capability, their volume and weight are also important issues, since higher volume and weight increase the injury risk for the user's head and neck.

Classical helmets from the ancient Greeks to today treat the head uniformly and are currently tested on rigid headforms. Anatomical helmets adapted to the inner head structure were invented by neurosurgeons at the end of the 20th century. Since the materials are disposed according to the anatomical structure of the head, they are smaller and lighter than the classical helmets.

Images

1500s helmet in forged steel (compatible Anachrome 3D).	Back of a SPECTRA helmet currently used in the French Military	Gordon Cooper in Helmet and Pressure Suit	Pith helmet of Harry S. Truman
A lacrosse helmet	A helmet used for rock climbing	Work safety helmet with visor	Motorcycle helmet.
Riotsquad helmet with back-of-the-neck protector	A bicycle helmet	Equestrian helmet for Horseback riding	Rendering of an American football helmet.
M1 Helmet in Vietnam.	Pickelhaube helmet.	Bulgarian M36 Helmet from World War II.

Types of helmets

Helmets used for different purposes differ greatly in their design. For example, a bicycle helmet would chiefly need to protect against blunt impact forces. A helmet designed for rock climbing, however, would need to protect against objects (e.g. small rocks and climbing equipment) falling from above. Consequently, bicycling and rock climbing helmets little resemble each other. Practical concerns also dictate helmet design: a bicycling helmet would preferably be aerodynamic in shape and probably well ventilated, while a rock climbing helmet would be lightweight and with a minimum of bulk to reduce any detrimental effect on the climber's technique.

Goggles, face guards and ear plugs are other forms of protective headgear. Hard hats are typically preferred in modern times for construction workers. Helmets are often used by riot police.

Sometimes medical conditions need a helmet to be worn to protect the brain because of a gap in the braincase, e.g. because of cleidocranial dysostosis or in separated craniopagus twins.

Heraldry

As the coat of arms was originally designed to distinguish combatants on the battlefield or in a tournament, even while covered in armour, it is not surprising that heraldic elements were often also used for the decoration of knightly helmets, while it was also possible to use different elements than on the shield, but equally standardized.

Furthermore, it became common to use a helmet (and/or some other headgear, e.g. a crown or coronet) as part of the coat of arms, above the shield, a practice maintained long after its use in reality was ended by military technology and the demise of jousting. In some systems, the rank of the bearer was reflected in the model of the emblematic helmet, e.g. the metal and the number of bars in the visor, as in France. Either way, the rank can be reflected by a coronet or wreath placed on the helmet (often instead of directly above the shield).

The heraldic convention in the United Kingdom is as follows:

Sovereign

• A barred helm of gold, placed affronté

Peers generally

• Barred helms of silver decorated with gold, placed sideways and showing five bars

Baronet's or Knight's helmet

Esquire's and Gentleman's helmet

• Closed helm or visored helm with visor down, Steel, placed sideways

See also

• Adrian helmet
• Baseball helmet
• Bicycle helmet
• Brodie helmet
• Bulgarian M36 Helmet
• Burgonet
• Corinthian helmet
• Cricket helmet
• Equestrian helmet
• PASGT ("Fritz") helmet
• Football helmet
• Great helm
• Horned helmet
• Kabuto (Samurai helmet)
• M1 helmet
• Motorcycle helmet
• Riotsquad helmet
• Pickelhaube
• Spangenhelm
• SPECTRA helmet
• Stahlhelm
• Aramid
• Twaron

Other meanings

• Helmet (band) is a musical band.
• Elmet is a post-Roman kingdom in north England.
• "Policeman's helmet" is a British colloquial name for the Himalayan Balsam plant, from the shape of its flowers.
• A slang term for the head (or tip) of the penis, due to the shape of this body part.