Helmet: - A helmet is a form of
protective gear worn on the
head to protect it from injuries, a variation of the hat. The oldest use of helmets was by Ancient Greek soldiers, who wore thick leather or bronze helmets to protect the head from
sword blows and
arrows. In the 2000s, soldiers still wear helmets, now often made from
Kevlar rather than metal, to protect the head from bullets and shell fragments.
In civilian life, helmets are used for recreational activities and sports (e.g.,
American football,
ice hockey,
cricket, and
rock climbing); dangerous work activities (e.g.,
construction,
mining,
riot police); and transportation (e.g.,
Motorcycle helmets and
bicycle helmets). Since the 1990s, most helmets are made from
resin or
plastic, which may be reinforced with fibers such as
aramids.
Military origins: - Helmets were among the newest forms of combat protection, and are known to have been worn by
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, particularly 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 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.
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.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.
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, to protect the wearer from non-ballistic injuries, such as concussive
shockwaves from
explosions, motor vehicle accidents, or falls. Military helmets can be worn with radio earmuffs, and other equipment such as night vision goggles, can be added. Military helmets are often worn with a removable cotton-polyester helmet cover, which allows the user to change the pattern of the camouflage (e.g., from dark green forest camouflage to tan-coloured desert camouflage).
Design: - Despite various designs and requirements, all 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. Anatomical helmets adapted to the inner head structure were invented by
neurosurgeons at the end of the 20th century.
Helmets used for different purposes have different designs. For example, a
bicycle helmet would chiefly need to protect against blunt impact forces from the wearer's head striking the road or a car hood. A helmet designed for rock climbing, however, would need to protect against objects (e.g. small rocks and
climbing equipment) such as an ice axe falling from above. 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 so that it would not interfere with climbing.
Some helmets have other protective elements attached to them, such as a face
visors or
goggles or a
face cage, and
ear plugs and other forms of
protective headgear, and a communications system. American football, hockey, and lacrosse helmets usually have an integrated face protector (
face cage) made from metal.
Baseball batting helmets have an expanded protection over the ear, which protects the jaw from injury.
Motorcycle helmets often have flip-down face screens for rain and wind protection, and they may also have projecting visors to protect the eyes from glare.
Hard hats for construction workers are worn mainly to protect the wearer from falling objects such as tools.
Helmets for
riot police often have flip-down clear visors and thick padding to protect the back of the neck.
Modern firefighter's helmets protect the face and back of the head against impact, fires and electricity, and they can include masks, communication systems, and other accessories.
Welding helmets protect the eyes and face and neck from flash burn, ultraviolet light, sparks and heat. They have a small window, called a lens shade, through which the welder looks at the weld; for
arc welding this window must be much darker than in
blowtorch goggles and
sunglasses.
In rare cases, people with some medical conditions must wear a helmet to protect the brain, due to a gap in the
braincase, e.g. because of
cleidocranial dysostosis or in separated
craniopagus twins.
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