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A crash helmet is a protective helmet which is designed to prevent head injuries in a crash. These helmets are required by law in many regions of the world, in response to numerous scientific studies which have demonstrated that wearing a helmet in a crash greatly reduces the risk of injuries. In areas where such helmets are not required, they are often in common use among cyclists, motorcyclists, and other individuals who are vulnerable to injuries in crashes.
The crash helmet design owes a lot to T.E. Lawrence, otherwise known as Lawrence of Arabia. Lawrence was involved in a motorcycle collision in 1935 which led to his death as a result of head injuries. One of the surgeons who worked on the case, Hugh Cairns, took note of Lawrence's head injuries and the growing numbers of head injury cases he saw as a result of road traffic accidents, and he decided that perhaps it was time to design effective protective headwear to reduce fatalities in crashes.
Typically, a crash helmet has a hard outer shell which is designed to resist penetration, and a thick foam inner lining which may be reinforced with carbon fiber or Kevlar®. This inner lining cushions the head in the event of a crash, reducing the risk of a skull fracture or other serious head injury. As a general rule, once a crash helmet has been involved in an accident, it must be discarded, even if it appears to be in good shape, because the integrity of the helmet may have been compromised.
There are a number of different styles of crash helmet, all of which are designed to cover the head and at least part of the face. The helmet is affixed with a chin strap which must be adjusted to ensure that the helmet is snug, and padding in the helmet may be adjustable to get the perfect fit. It is important to fit a crash helmet properly, so that it does not wiggle or move on the head, as an ill-fitting helmet will not provide adequate protection in a collision. One of the safest designs is the full-face, a design which includes a chin bar with a slit for the eyes, but it is also possible to find other versions.
In addition to bicyclists and motorcyclists, some other people can benefit from wearing a crash helmet, ideally a helmet designed for their particular activity. Test pilots, stunt drivers, horseback riders, race car drivers, and people who engage in various motocross sports should all wear crash helmets for protection. The use of helmets is also strongly recommended for many sports, including American football, hockey, lacrosse, and hang gliding.
Most nations have helmet standards which are set by government agencies. These standards are arrived at by testing various helmet designs and materials, and they include minimum specifications in terms of coverage, load-bearing ability, and so forth. People should take care to purchase helmets appropriate for their activities which have designs approved by the government for safety.