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Can You Keep A Cool Head

Published: 10th Oct 2008

ARTICLE CONTINUES BELOW

In a previous HSI article (October 2006 - “If you want to keep your head, wear the right hat”) I wrote about head protection. The topics covered included causes of head injury, how and when helmets protect you, regulations and standards, types of helmet and SUCAM (Selection, Use, Care And Maintenance).

This article provides a selection of some more useful and (hopefully) interesting points about head protection not covered in my previous article.

Some reminders about head protection and its use

Head protection in PPE terms is considered as protection against impact injury and some burn injuries. It generally protects the scalp area, and sometimes the jaw. The face is generally not included, except for some sports helmets. (Protection for the face is generally covered under “eye and face” protection or sometimes by full-face RPE.) The general aims of head protection are very simple:

  • To reduce the level of the force/acceleration on the head to an “acceptable” level
  • To prevent objects cutting or penetrating the head
  • Choosing the right head protection, and then using it correctly, is not that difficult and is a very good investment.

    Head protection generally falls under the same regulations as other PPE - in the UK this is The PPE at Work Regulations 19921 and The PPE Regulations 20022. Some key points of these regulations are:

    • Head protection should only be used after a risk assessment has been made
    • Head protection should be selected, used and maintained correctly
    • head protection should be CE marked (to show that it meets the essential safety requirements of the PPE Directive 89/686/EEC)

    Correct selection, use, care and maintenance is essential for you to get the best performance from your head protection. All head protection should come with full instructions, and the manufacturer or supplier can provide more information. You should always follow the manufacturer’s instructions. As with any PPE, you can get detailed advice from manufacturers, suppliers and safety organizations and regulators; HSE in the UK 3.

    As for all sensible risk management, you need to assess the hazards and risks and take steps to reduce the risks until they are “as low as is reasonably practicable” (ALARP). Because head protection only protects the wearer and does not remove the hazard it is the last line of defence. Before choosing PPE you should try to remove the hazard or make the hazard less severe.

    MOST IMPORTANTLY, REMEMBER THAT HEAD PROTECTION DOES NOT OFFER 100% PROTECTION AGAINST ALL HAZARDS - IT ONLY PROTECTS AGAINST DEFINED HAZARDS AND ONLY REDUCES INJURIES TO AN ACCEPTABLE LEVEL.

    Comfort and wearability - EN 397 safety helmets

    Comfort is one of the biggest issues affecting all PPE, not just helmets. As with any PPE, if a helmet is more comfortable then it’s more likely to be worn. I’m using the EN 397 safety helmet as an example here, but the same principles will apply to any helmet.

    When you judge how comfortable a helmet is you are combining a number of different factors. These include the helmet’s mass, balance, tightness of fit and how hot or cold it makes you feel. But these aren’t just single factors, they affect each other - often if one factor is worse you feel other factors are worse as well, even when they probably aren’t. And your feeling of comfort can be affected by your expectations - if you think a helmet will be uncomfortable before you put it on then it probably will feel uncomfortable when you do put it on! With this complex mix of factors affecting comfort it’s not surprising that it can be difficult for helmet designers to assess the biggest cause of discomfort.

    You may be surprised how much difference there can be in the “feeling on the head” of apparently similar safety helmets. The balance of the helmet and the exact position of the cradle on your head can have a big effect on how it feels - two different helmets of the same mass can feel very different. Even though safety helmets have a lot of dimensions fixed by EN 397, their mass, balance and fit can still vary a lot.

    The best way to find a comfortable helmet is to try a selection - but this isn’t always practical. Here are some points to consider.

    • The cradle - add a comfort/sweat band over the plastic, keep the band clean and replace it when it gets thin or worn
    • Fitting - check the cradle adjustment - and, particularly if you’re Head Protection bending a lot, a chinstrap should make your helmet more secure
    • Sizes - large and small helmets are generally available if you ask the manufacturer or supplier
    • Helmet mounted earmuffs can affect how the helmet feels and balances, especially when off the ears
    • An integral visor or a helmet-mounted faceshield may be more comfortable and suitable than separate goggles or glasses
    • Are you wearing the helmet over a hood (e.g. a suit for chemical protection) ?
    • Are you wearing the helmet with a respirator ?
    • Is the retention system correctly adjusted - e.g. bicycles and motorcycles where a helmet which feels tight will fly off in an accident if the chinstrap isn’t properly adjusted and fastened

    The biggest problem with helmets is often that they make your head feel uncomfortably hot. The good news is that, under most circumstances in the UK, you won’t get hot enough to affect your health because of your helmet. (Of course, other clothing or simple sun on the rest of your body could make you ill, but it wouldn’t be caused just by the effect of the helmet on your head.) Indeed, under direct sun in the middle of summer (maybe not this year, but we can dream...!) the helmet might make your head feel hot but will protect against sunburn.

    It’s not just the heat (i.e. temperature) which affects your comfort. Humidity and air movement also affect how comfortable you feel. At low or high humidities you’re more sensitive to temperature effects, and draughts or the wind can make you feel cold on a hot day.

    Helmet ventilation holes

    Again, I’m using the EN 397 safety helmet as an example here, but the same principles will apply to any helmet. Some safety helmets can have ventilation holes - electrical and molten metal protection versions can’t. These holes are intended to allow more air movement between the helmet and your head. This should reduce the temperature and humidity close to your head so that you feel more comfortable when it’s hot. (You might also feel less comfortable when it’s cold or wet...) The exact position, number and size of these holes will affect the ventilation and comfort of the helmet. BUT, this effect is not always easy to predict, as the amount and direction of breeze can have a big influence on how much cooling effect the ventilation holes have. Often it is the clearance between the edges of the helmet and your head that has the biggest effect on how much cooling your head will get from the breeze. Also, how much hair you have will change how ventilation affects your comfort!

    Because of the importance of ventilation and comfort, the heating effect of safety helmets, and in particular the effect of ventilation, is being studied by different researchers and manufacturers.

    Please, please DO NOT ADD YOU OWN VENTILATION HOLES, especially large ones, as this could weaken the helmet and allow bigger objects to get through and hurt you. The most effective way to make yourself feel cooler is often to take a quick break where you can wipe your head down and splash on some cool water.

    It is worth remembering that the holes which can cool your head in summer can also let the rain in, and can make you feel colder during the winter. Perhaps you need summer and winter helmets... not as impractical as you might think. Helmet liners designed to be worn with helmets are available to keep your head warm in winter.

    For safety helmets, the ventilation holes must not be larger than a certain size so that the risk of an object getting through is small, and the object which could get through can’t be very big so it shouldn’t be able to do much damage.

    Bicycle and motorcycle helmets also feature ventilation holes or systems, but these are designed to work while you are on the move rather than stopped. Because of the air movement, the ventilation can cause noise, especially at higher speeds.

    Neck injuries

    There is always debate about the effect of wearing a helmet on neck injury, particularly for bicycle and motorcycle helmets. The neck is a very complex system to model, and its impact response is influenced by other parts of the body. Interesting research on Head Protection“Biofidelic Surrogate Necks” (i.e. like a crash test dummy, but only modelling the neck or neck and head) is increasing our knowledge of neck injury mechanisms, especially for “head-on” impacts. Purely on name, my favourite is “Frankenspine” (www.pronecktor.com - this site is referenced for information and not as any endorsement of products or services).

    There is no doubt that it is possible to devise accident scenarios where a helmet may increase the risk of a neck injury. However, when you consider all the possible accident scenarios the number where a helmet might increase injury to the neck are always very much smaller than the number where a helmet would reduce injury to the head or neck. And you must remember that helmets are intended to reduce the severity of the total injury, and not to eliminate all injury.

    As an example of how important it is to consider the whole picture, there have been times when improvements in military helmets resulted in increased numbers of head injuries being reported in combat. This sounds like an argument against wearing these helmets, until you remember that the increase in injuries was accompanied by a reduction in deaths - those who used to die were only injured because of the greater protection from the helmet.

    Rotational head injuries

    There is also debate about the ability of helmets to protect against rotational brain injuries i.e. where the impact causes rotational motion on the brain inside the skull. Some studies have reported that in some circumstances a helmet can cause a rotational brain injury. Friction between the outer surface of the helmet and the surface that it contacts during impact is thought to cause these injuries. The rotational effect is larger with a helmet because it projects away from the head so there is greater “leverage” and rotational force the bigger the helmet is.

    This problem is most likely for motorcycle, bicycle and some sports helmets. BUT, again, if you look at the whole picture then an increased risk of rotational injury in some scenarios is outweighed by the protection provided against other forms of brain and head injury, and by the scenarios where rotational effects are not strong.

    Also, there are now helmets with a soft outside covering which tears or strips away during impact. This is intended to reduce the friction, and therefore also reduce the rotational force (www.mipshelmet.se is an example - this site is referenced for information and not as any endorsement of products or services). A similar principle uses two helmet shells which can move independently (www.pronecktor.com is an example - this site is referenced for information and not as any endorsement of products or services).

    There is no doubt that helmets save many lives, and reduce many injuries. I have personally investigated incidents where helmets have saved lives and I would always wear a suitable helmet.

    Helmets after impact

    Again, I’m using the EN 397 safety helmet as an example here, but the same principles will apply to any helmet. Helmets are designed to protect against a single impact event. After a large impact it may be very obvious that they are damaged e.g. holes, cracks, broken cradle, compressed foam. But, particularly after smaller impacts, there may not be obvious damage e.g. the cradle anchors may be weakened or slightly stretched, foam may be a little bit compressed. Or it may be difficult to see the part of the helmet affected by the impact e.g. the layers of foam in some motorcycle helmets. Even though you can’t see this damage, it will reduce the protection from the helmet at the next impact. So, the rule is always replace your helmet after an impact. Safety helmets are very cheap and so this is easy, but even more expensive helmets are still much cheaper for you than an avoidable stay in hospital and possible long term ill-health.

    The best rule is “if in doubt, replace”.

    US (ANSI) and UK/European (CEN) standards

    The standards in the US and Europe are usually different. US uses ANSI standards while Europe uses CEN (EN) standards. At the moment there is no action on developing international (ISO) standards for industrial head protection, but there are a few ISO standards for other head protection e.g. EN ISO 10256 - Head and face protection for use in ice hockey.

    ANSI and EN standards are often similar, but not exactly the same. For example, industrial safety helmets are covered by ANSI Z89.1-2003 and EN 397, but these standards are not quite the same. While a manufacturer might make a helmet that could be certified to both standards, it is common for manufacturers to make slightly different helmets for US and European markets. If you see a US ANSI helmet which you like, check with the manufacturer if there is a European version. The PPE that you use in Europe must be CE marked, so don’t just bring an ANSI helmet into Europe and use it.

    The same often applies to other international standards e.g. Australian, New Zealand, Japanese etc.

    New helmet designs

    Recent helmet standards have been written to have performance requirements with as little restriction on design as possible, so that new technologies can be used as they develop. For example, there have been significant advances in the performance and cheapness of impact absorbing foams.

    Older standards may have design restrictions based on what technology was possible when the standard was first written. This may not allow the use of new technologies. An example of this is EN 397, which specifies clearances and so does not allow foam inserts. CEN TC158, the European standards group which covers head protection, has advised that if you want to make a new design of safety helmet then you can use the alternative standard EN 14052:2005 “High performance industrial helmets” which does not have the design restrictions of EN 397 but has similar performance requirements. Since products made to EN 397 have a long history of offering good protection, there is no strong desire to change EN 397 when EN 14052 will allow the development of new and innovative designs.

    Some helmet designs now feature a two piece helmet. For example, firefighters helmets can have a general purpose inner helmet for use all the time when flame and heat are not present, and a flame and heat outer helmet which is added as needed (www.helmets.co.uk is an example - this site is referenced for information and not as any endorsement of products or services).

    Information on helmets and reporting problems

    Many helmet manufacturers are interested in getting information on how their helmets have performed during impact, and would welcome you telling them. Some manufacturers keep this information in-house while others publicise it. For leisure helmets, there may be a user or interest group which is interested in getting data on accidents and helmet performance.

    For example, the British Mountaineering Council (www.thebmc.co.uk) collects information on helmet performance in climbing accidents. (BMC can also provide information on helmet performance.)

    If you have a problem with a helmet not performing as well as you think it should, you can contact the manufacturer. You can also contact HSE or a Local Authority (Trading Standards) in the UK, or the relevant Health and Safety Authority in other countries. If you think there are issues about a standard for head protection then you can contact BSI or CEN (and HSE may also be worth contacting as it has input to the standards process).

    In some leisure areas you will now find there is independent information available on the performance of different helmets.

    For motorcycle helmets, the UK Government SHARP scheme (www.sharp.direct.gov.uk) rates helmets up to five stars on aspects of their protective performance.

    The Equestrian New Helmet Assessment Programme (ENHAP - www.mdirf.co.uk) provides information on the protective performance of riding helmets, but has been the subject of debate among manufacturers and the riding sector.

    Other helmets

    The UK police have their own standards for some types of helmet (e.g. riot helmets) as well as using “ordinary” commercially available helmets. Other emergency services use helmets designed for their work but based on commercially available helmet standards. Military helmets are usually to military standards, but some “ordinary” commercially available helmets are used e.g. hard hats in non-combat construction areas. Not all the designs and technologies in police, emergency service and military helmets are more advanced than those in commercial helmets, and with time any useful new designs and technologies tend to become used in commercial helmets.

    Diving helmets are an interesting niche area. Glass fibre diving helmets with clear faceplates are primarily designed for breathing rather than for impact or other protection. But, clearly, they will offer some impact protection. And there are impact hazards for divers from both fixed and moving objects. As these helmets cost around £3000 they will probably need to continue in use after some impacts (although not after major impacts). UK HSE has been conducting some impact testing on diving helmets to compare their performance with the requirements for EN 397 helmets for both single and multiple impacts. Diving helmets have a rigid shell with a screwed down faceplate and a padded foam “hood” worn inside the helmet. This gives a number of variables for impact protection. Even though it is “rigid”, the metal shell will have temporary deformation during impact which can be quite large. These tests have illustrated the influence of the type and thickness of foam padding used inside the helmet on the impact protection provided, particularly for multiple impacts.

    Martial arts head protectors illustrate the importance of understanding the protection offered before using head protection. These look like boxing headguards, and are mostly made of lightweight foam. You might think they give the wearer protection from deliberate kicks and punches to the head. However, BS EN 13277-4:2001 “Protective equipment for martial arts - Part 4: Additional requirements and test methods for head protectors” states that these head protectors “are designed to provide a degree of safety in case of accidental contact during martial arts. Martial arts can be dangerous and severe blows to the head may cause serious injury even if the protector is fitted and used properly.” So, if you don’t understand this limit to the intended head protection you could expose yourself to the risk of serious injury.

    Questions I am asked

    Most frequent question - helmet lifetime ?

    Answer (covered in my previous article) - in general for safety helmets 3 to 5 years if stored and used correctly. It is best to ask the manufacturer or supplier, especially if it is used in a chemical or hot environment. Always replace after an impact or if the helmet looks too worn or damaged.

    Can I use an ANSI helmet ?

    Answer - Not without a CE mark. See earlier in the article.

    Must an imported helmet be CE marked ?

    Answer - yes. This is the responsibility of the importer to the EU (or the manufacturer if inside the EU).

    Are small helmets available ?

    Answer - generally yes. See earlier in the article.

    Is there any information on risks from dropped objects ?

    Answer - yes. DROPS has charts of risk for different object mass and drop height (www.dropsworkpack.com). You need to use this information with care, and err on the side of caution, but it is a useful indicator.

    My helmet falls off when I bend over or the wind blows hard.

    Answer - use a chinstrap. All safety helmets will have an optional chinstrap.

    Is a bump cap ok for protection against falling objects ?

    Answer - NO, it is only designed for the bump hazard of you hitting a fixed object. Use a safety helmet for falling objects.

    Can I phone HSE for PPE advice ?

    Answer - YES - you can phone HSE for advice on any aspect of health and safety. HSE is not just a regulator, it also gives lots of guidance and advice. HSE Infoline3 0845 345 0055.

    Finally, based on a question I have received, the peak of the EN 397 helmet is not tested for any protective performance. So a peak cannot be “too flexible” as its performance is not specified in EN 397. And helmets without a peak for those who need to look up a lot in their work (e.g. for linesmen) are allowed in EN 397.

    In summary, there is a wide range of head protection suitable for almost all your needs. If you apply sensible risk management and an appreciation of the limitations of the protection offered by head protection then you can keep your head safe for its designed lifetime.

    References

  • The Personal Protective Equipment at Work Regulations 1992 maintain the implementation of the Personal Protective Equipment at Work Directive 89/656/EEC. HSE publication L25 “Personal protective equipment at work (Second Edition)” ISBN 0717661393 gives these regulations and associated guidance
  • The Personal Protective Equipment Regulations 2002 (SI 2002 No. 1144) maintain the implementation of the Personal Protective Equipment Directive 89/686/EEC and are produced by DTI
  • HSE infoline 0845 345 0055, HSE website www.hse.gov.uk
  • The author would like to thank colleagues in HSE and other members of the British and European Head Protection Standards committees for many of the data and ideas used in this article.

    © CROWN COPYRIGHT 2008

    Published: 10th Oct 2008 in Health and Safety International

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