Keeping Your Head
Published: 10th Jan 2003
Helmets today are well designed and can offer significant protection if carefully selected, used, and maintained. Improved helmets are on the way, but there is no need to wait; increased use of existing helmets would greatly reduce the number of head injuries.
Many human activities involve a risk of head injury. Before reaching for a helmet, it is always worth considering the hierarchy of protection against risk of injury:
- Is the activity really necessary?
- Can an alternative safer activity be substituted?
- Can protective measures other than Personal Protective Equipment (PPE) be applied?
Only if the answer to these questions is “no” should PPE be used.
When the hierarchy of alternative protective measures has been applied there are still many situations where head protection by PPE is required. In this article head protection refers to skull protection i.e. the area typically covered by a helmet. Eye, face and ear protection are beyond the scope of this article. Most types of helmets now used are covered by standards. Standards can be task specific, such as those for a cycle helmet or a fire fighter’s helmet. Alternatively, they can be generic, such as the child’s play helmet or the industrial safety helmet. I shall deal mainly with industrial helmets but some of my comments apply equally to other types.
In this article I will present some of the background to head protection and talk about selection, use, and maintenance. This is a personal view from the perspective of the situation in the UK. The article ends with a look at possible future developments.
How Helmets Work
So why do we need head protection? In a typical scenario, a piece of wood falling from a scaffold will have a mass (M) and a velocity (V). The wood is said to have energy given by the formula:
Energy = 1/2 MV 2
On hitting an unprotected head the velocity of the wood may quickly drop to zero. Applying the same equation this means the energy is now zero, but where has the energy gone? It has been absorbed by the head: it has been used up in lacerating the skin, fracturing the skull, compressing vertebrae, tearing blood vessels to the brain, and damaging brain cells. In short, a recipe for debilitating injury or death.
Head protection operates by suffering damage during an impact. The head protection is destroyed instead of the head. Three protection mechanisms are in common use. Head protection may have a rigid outer shell that absorbs energy by being lacerated, broken or deformed. Secondly, it may have a layer of compressible high-density foam; this absorbs energy by being crushed. Finally head protection may have a harness consisting of plastic or fabric tapes that stretch or tear during impact.
Not all helmets use all three mechanisms.
A protective helmet absorbs energy by sustaining damage and after being damaged its ability to absorb further energy is decreased. If a helmet suffers an impact it should be replaced; it may look OK but it isn’t. The harness of a helmet must be able to stretch for it to absorb energy and it is essential that there is a gap between the harness and the inner surface of the helmet to allow for this stretching. Wearers should always choose the correct size helmet and adjust a harness according to the manufacturer’s instructions.
In old photographs, industrial workers are invariably seen wearing flat caps. Anecdotally some workers lined their caps with layers of newspaper. This may have been more about having something to read with their sandwiches than a source of head protection. Some industries developed a more systematic approach and by the 1950’s all miners wore a safety helmet of sorts. The development of modern plastics and the introduction of national standards and international standards, coupled with increasing legislation have led to the industrial helmets now available.
Similar developments have been seen in sporting helmets. For example the wearing of a bowler hat by horse riders has given way to purpose made protective headwear meeting a standard.
The present situation is that helmets offer more protection, are more comfortable, and users are better informed than ever before. However, many people see helmets as hot, uncomfortable, having a poor image, and unnecessary. There is a reluctance by many people to wear head protection. Sadly this is reflected in significant numbers of head injuries each year. The following statistics have been provided by the UK, Health and Safety Executive, Statistics Unit and refer to injuries at work for the year 2000/2001.
|Percentage of Fatal Head Injuries by 5 Industry Sectors|
Of 213 fatal injuries during the year 22% were head injuries Of 26,547 major injuries during the year 7% were head injuries Head injuries are not confined to any one industry but occur across a range of industries. Although head injuries only represent 7% of injuries, they form 22% of fatal injuries. In other words injuries to the head are more likely to prove fatal than injuries to other parts of the body. From a study of accident reports, it is clear that many head injuries are sustained by people not wearing helmets, however, in some cases the impacts are so severe that injuries occurred even though a helmet was worn.
Selection of head protection for any task hinges upon an effective risk assessment. Following the risk assessment the hierarchy of control measures should be applied, and only if there is a residual risk is head protective PPE necessary. Clearly, in the statistics given above, risk assessment has been absent or inadequate in many cases.
For sporting activities the choice of helmet should be straightforward; many sports now have head protection purposely made for that activity. In effect someone with knowledge of the hazards of the sport has done the risk assessment and written a standard for a suitable helmet.
Selection of industrial head protection is not always so simple. The wide range of industrial processes and environments results in a great variety of risk assessments. The two industrial helmets widely used in Europe are the industrial safety helmet and the bump cap. European standards exist for both these types of head protection.
The industrial safety helmet is designed and tested to protect against falling objects striking the crown of the helmet. It is not tested against side impact. The helmet also protects against penetration by sharp objects, flame spread and optionally can protect against electricity, molten metal, and crushing. The industrial safety helmet utilises a hard shell and a harness to provide energy absorption. The amount of protection offered against any of these hazards is generally significant but does have a limit. No helmet can guarantee the complete safety of the wearer. In the case of impact by a falling object, as described earlier, the helmet absorbs energy. When its capacity for energy absorption is reached or exceeded the helmet ceases to be effective and no further protection is provided.
The bump cap is designed and tested to protect the head of someone who walks into an obstruction or stands up in restricted headroom. The bump cap is unsuitable for protection against a falling or moving object. Optional protection is available against flame spread and electricity. The bump cap can utilise any or all of the three safety mechanisms described earlier, but it is generally less protective than an industrial safety helmet.
For the majority of industrial environments the risk assessment requirements can be met by choosing an industrial safety helmet meeting European standard EN 397 or a bump cap meeting EN 812. But for many environments there are other factors, which will influence the choice of helmet make and material. Helmets may need to be used at high or low extremes of temperature. Certain chemicals may cause rapid deterioration of some helmet plastics robbing them of energy absorbing properties and shortening the lifetime of the helmet.
Risk assessment may show that other hazards are in the workplace. Eye protectors, ear defenders and respirators may all need to be used in conjunction with the helmet. It is essential that each item of PPE worn is compatible with the others. Compatibility is about wearer comfort and the continued performance of each item. In such cases the helmet manufacturer is a valuable source of information. Helmets are made in a number of materials and with a range of accessories; the manufacturer will advise which is best for your application.
Occasionally, an industrial safety helmet or a bump cap cannot meet the requirements of a risk assessment. In this situation another form of helmet may be chosen. For instance, electrical linesmen are involved in a number of tasks including driving all terrain vehicles. Linesmen often wear mountaineers helmets. This helmet is not ideal for their work but is considered a compromise that best matches the risk assessment. Such a compromise is acceptable provided it is supported by a robust risk assessment.
In general, all PPE sold or used in Europe, including the UK, must carry the CE mark. The CE mark means that a helmet has been tested and approved, by a government appointed body, as complying with the EU PPE directive. Having a helmet approved and CE marked is the responsibility of the manufacturer. If the helmet is manufactured outside the EU, the importer takes on the responsibility. If an employer sources and buys helmets outside the EU, the employer becomes the importer and takes on the responsibility for having the helmet approved and CE marked.
Wearers of head protection should have some training in the care and performance of their helmet.
Wearers should be encouraged to respect their helmet; it should never double as a makeshift hammer or bucket. A helmet can only deliver its potential protection if adjusted and worn correctly. Helmet size should be appropriate for the wearer and the harness should be tight but comfortable. The practice of reversing helmets on the head prevents the helmet functioning as designed. In an impact the helmet will not provide its maximum protection. Would you rather be uncool or out cold? Helmets should not be modified in any way. The “extra ventilation”, shown in the photograph, has weakened the shell and sharp objects could readily penetrate the helmet.
Chemicals can damage plastics and this includes some paints and adhesives; helmets should never be decorated or marked with paint or stick on labels without the specific approval of the manufacturer. In harsh environments helmets inevitably collect cuts and scrapes. Each cut and scrape reduces the effectiveness of the helmet slightly and collectively can weaken the helmet significantly. Helmets should be discarded before they look like the one in the photograph, which had suffered many years of abuse.
If a helmet suffers an impact it should be replaced immediately or as soon as practicable.
Wearers should have an understanding of how much protection they can expect from their helmet. A wearer of an industrial safety helmet can expect reasonable protection from a falling object of 5 kilogram mass with a velocity of approximately 5 metres per second. In real life this could be a house brick falling from 1 metre. If the mass is greater than 5 kilogram or it falls from more than 1 metre, the protection offered will be reduced. Wearing head protection is never a substitute for safe working practice.
When an employer supplies helmets to the work force or a sportsman buys head protection they should give some thought to maintenance. In hot environments a sweat band can be fitted to the harness of some helmets. This improves the comfort of the helmet. Unfortunately sweat bands and harnesses can pose a health risk by becoming contaminated and causing dermatitis. Sweat bands and harnesses require cleaning or replacing according to the manufacturer’s instructions.
Helmet plastic can react with oxygen when in sunlight, resulting in a gradual loss in energy absorbing properties. Whenever possible, helmets should be stored in a clean place away from direct sunlight when not in use. If being stored for any length of time they should be in a bag. Everyone who buys a helmet should have a policy on replacement. The lifetime of a helmet depends on usage, wear and tear, environment, exposure to sunlight, and the helmet material. Expense is clearly an issue in helmet replacement. It may be a choice between buying a cheap helmet and changing it frequently, or a more expensive helmet, which gives a longer life. There is no place for a worn out helmet in head protection, except the bin.
Currently there are changes in the pipeline for industrial head protection. There are three main deficiencies in industrial head protection. The industrial safety helmet meeting standard EN 397 is only designed to protect against downward impact to the crown, with little protection against side impacts. The limit of impact protection is a 5kg mass dropping from 1 metre.
Although protection will always be limited in a wearable helmet, modern materials now allow standards to set a higher energy impact test. The limited number of options available and the absence of side protection can make it difficult for the industrial safety helmet to meet the requirements of a risk assessment resulting in the compromise selections mentioned earlier.
European standard makers are currently working on a new standard for a high performance industrial helmet. The requirements of this new standard will increase the level of protection available and widen the range of options. Side impact tests will be included in the standard. The energy used in the crown impact will be double that of the current test. With the increased protection, side impact protection plus other options, which may be included, there should be fewer occasions calling for compromise in helmet selection. There are ongoing improvements in wearer comfort and protection, but in my opinion, there will always be a trade off, with comfort being sacrificed to achieve protection.
Published: 10th Jan 2003 in Health and Safety International