When people talk about protection in the context of health and safety, it’s generally about Personal Protective Equipment (PPE). No worries – I’m not going to disappoint you. You’ll get my views on PPE in respect of Hand-arm Vibration (HAV) shortly, but I make no apologies for reiterating an old Health and Safety Executive (HSE) favourite first.
By far and away the most effective form of protection is, wherever and whenever possible, to eliminate the risk. If you can’t achieve that then it’s control and management. While PPE has its uses and should be properly worn and maintained, it should never be forgotten that when it fails, it fails to be safe.
The trouble is, give PPE to some folk and they seem to think they become immune from danger and acquire immortality. Sadly the truth is altogether different.
How many shattered lives are testimony to that?
General health and safety regulations, supported by HSE guidance, have required employers to control the risks from vibration and protect their employees since the early 1990s; however, the Control of Vibration at Work Regulations 2005 (hereafter called the Regulations), place specific duties on employers. They are based on a European Union directive requiring similar basic laws throughout the union on reducing the risks of vibration-related diseases.
Before considering the PPE, let us first review the need to assess the risk. It is from there, and only there, that all other action should stem.
The Vibration Regulations require that Dutyholders make a ‘suitable and sufficient’ assessment of the risks from vibration. This includes:
• Identifying employees who may be at risk from exposure to HAV
• A soundly based estimate of the employees’ likely vibration exposures compared with the exposure action value and exposure limit value
• The available and appropriate options for controlling risk
• The steps that are planned to be taken to control and monitor those risks and a record of:
• The assessment
• The person(s) responsible for the assessment
• The control measures you have taken and their effectiveness
• Your plans for further action
Five steps to vibration risk assessment
There are five basic steps in assessing the risks from HAV at work:
• Step 1.
Look to see whether there is a vibration problem to manage, e.g. whether HAV is likely to be a significant hazard in the workplace
• Step 2.
Identify all workers likely to be exposed above the daily exposure action value or above the exposure limit value
• Step 3.
Stop work which exposes employees to vibration above the limit value. Where employees are likely to be exposed to vibration above the exposure action value plan to introduce a programme of controls to eliminate risk, or reduce exposure to as low a level as is reasonably practicable. Introduce health surveillance for those employees who are likely to be regularly exposed to vibration above the action value
• Step 4.
Record the findings
• Step 5.
Review the assessment and revise it as required
It’s important to remember that assessing the risk includes more than just calculating daily exposures, as working conditions and musculo-skeletal ergonomics can also have a major impact on the health of those at risk.
If any employees are particularly likely to be affected by exposure to vibration this should be taken into account when planning to control the risk. If any vibration-exposed employees have HAVS, other diseases of the hands, arms, wrists or shoulders (e.g. carpal tunnel syndrome), diseases affecting blood circulation (e.g. diabetes) or certain other disorders, advice should taken from an occupational health service provider on individual employees’ fitness to work with the vibration exposure.
The Regulations also require the pattern of vibration exposure in addition to the level of daily exposure to be considered. For example, if the daily exposure occurs over several periods with breaks between them, the risk to health may be less than a long period of uninterrupted exposure.
An action plan to manage the risk
While the vibration exposures (having identified the work processes which cause them) are being assessed, thought should be given as to how to eliminate or reduce exposures. The process of risk assessment leads to the identification of reasonably practicable controls and is not complete until an action plan for risk control has been developed.
An action plan is an important stage in the risk management/control process, and should include the following:
• Identify the significant sources of vibration • Prioritise them as contributors to risk (exposure) • Identify and evaluate solutions in terms of practicability and cost • Plan the introduction of reasonably practicable controls, with timescales • Plan the introduction of health surveillance if exposures are still likely to exceed the action value • Define management responsibilities and allocate adequate resources to implement controls, evaluate them and monitor progress
The basic methods for reducing vibration exposure and risk, in approximate order of effectiveness, are:
• Eliminate the use of vibrating tools or equipment by introducing mechanisation or alternative, vibration-free processes
• Reduce vibration exposures by modifying the existing process
• Replace power tools with suitable modern, efficient, ergonomic, vibration-reduced types through an effective purchasing policy
• Select appropriate consumables (e.g. better-balanced and fitted grinding wheels) and replace them when required
• Provide employees with training, information and instruction on safe use of tools and equipment and ensure adequate supervision
• Carry out maintenance of tools and equipment and replace consumables, as recommended by the manufacturer
• Minimise the forces needed to operate and control the tools (e.g. with tensioners, balancers, jigs, fixtures)
• Reduce the exposure time, e.g. through job rotation
The approach you should take will depend on the availability of reasonably practicable controls, technical advances and the current levels of exposure.
For some high-vibration tools there may be no lower-vibration alternatives available, and control through reduction of exposure time may not be reasonably practicable. You should investigate options for the introduction of new processes to eliminate or reduce vibration exposures, particularly if the exposure limit value is exceeded. This may be part of your plans for future capital investment. (In the meantime you must reduce the exposures to the lowest level that is reasonably practicable).
For some high-vibration tools there are lower-vibration alternatives, which may allow you adequately to control the vibration exposure by careful selection and management of the tools you choose.
Where the tools produce sufficiently low vibration magnitudes it may be possible to continue to use them, and to control vibration exposures by limiting the daily exposure time and by training your operators to minimise the transmission of vibration to their fingers by correct use of the tools. This will require good supervision and regular review to ensure that the agreed procedures are being observed.
Health surveillance should also be provided for vibration-exposed employees who:
• Are likely to be regularly exposed above the action value of 2.5 m/s2 A(8)
• Are likely to be exposed occasionally above the action value, and where the risk assessment identifies that the frequency and severity of exposure may pose a risk to health
• Have a diagnosis of HAVS (even when exposed below the action value) and any others identified in the assessment as being at risk
Record your findings and action plan
The Vibration Regulations require that you keep a record of the significant findings of your assessment(s) and what must be done to control the risk. If the assessment shows that the daily exposures are low (e.g. clearly below the exposure action value), then the assessment record should explain this. Remember, however, even if your exposures are below the exposure action value, some employees may still be at risk.
The Vibration Regulations require you to eliminate the risk at source or to reduce it to the lowest level reasonably practicable.
When exposures are likely to exceed the exposure action value, the assessment should include an action plan showing the priorities for introducing vibration control measures.
So where does HSE stand on anti-vibration gloves? Well, I’m sorry to say that I’m probably going to surprise and upset a few people. Let me explain. As you are probably aware there are several different types of anti-vibration glove on the market, although many are only suitable for a restricted range of activities and in HSE’s view they aren’t generally effective at reducing the frequency-weighted vibration (e.g. vibration at the frequencies that have the greatest effect on vibration exposure).
The degree of vibration reduction provided by gloves generally depends on the thickness and softness of the lining, which is usually a resilient gel, foam or rubber-like material, or an array of air bladders. To protect against lower vibration frequencies the contact areas of the glove need to contain thicker resilient material. This may seriously limit dexterity and comfort and the gloves may therefore be unsafe to use, and unacceptable to employees. Gloves may also result in operators having to tighten their grip on the tool and, as a result, actually increase the risk of vibration injury.
Gloves marketed in Europe as ‘anti-vibration’ must carry the CE mark, indicating they have been tested and found to meet the requirements of the current standard, BS EN ISO 10819:1997.
This standard requires that anti-vibration gloves:
• On average, provide some protection against relatively high vibration frequencies (200 Hz and above)
• Do not, on average, increase vibration levels at lower frequencies
These requirements mean that the specified vibration reductions are not defined for individual vibration frequencies, but are based on the average over a wide range of frequencies.
Therefore, some gloves may increase, rather than reduce, vibration at particular frequencies and still meet the requirements of the standard. This could result in an increase in the overall vibration exposure if the tool or process happens to vibrate at the glove’s resonance frequency.
Gloves will generally perform best at the higher frequencies, with little effect at low and medium frequencies. This means they can pass the standard test and still produce only negligible or moderate reductions in the frequency-weighted vibration magnitude at the hand. This is because of the shape of the frequency weighting, which assumes that the lower frequencies of vibration have the greatest effect on health.
The standard test considers only the reduction of vibration in one direction, at the palm of the hand. There is no information about the performance of the glove in three directions, or at the fingers. In practice this means that it is not usually possible to predict a ‘protected’ level of vibration exposure inside the glove.
The absence of detailed performance data for gloves means it is difficult for employers to assess adequately the protection given by anti-vibration gloves, as required by the PPE at Work Regulations, 1992.
Additional testing of the vibration characteristics of the tool or process, in combination with the glove would be required, and experience to date has shown that the results are generally disappointing. Exceptionally, testing may show that the gloves are likely to be effective in specific circumstances, but this should be demonstrated, and all other reasonably practicable exposure control measures are still required under the Vibration Regulations.
Manufacturers continue to conduct research to develop materials for gloves, which can provide substantial reductions in vibration across a wider range of frequencies. Any revision?to BS EN ISO 10819:1997 may require glove manufacturers in the future to provide better information with which to compare gloves and assess the protection they provide. However, it seems unlikely that an adequate assessment will be possible using standardised information provided by the supplier.
In the meantime, employers should not assume anti-vibration gloves will reduce vibration exposures unless test data confirms this for the particular combination of glove and tool used.
Gloves may be a useful supplementary measure which, at least, ensures that operators protect their hands and keep them warm, and may be beneficial in reducing the higher frequencies of vibration. However, anti-vibration gloves alone should not be relied on to significantly reduce vibration exposures. A pair of good quality industrial gloves will often provide equal levels of protection.
Additionally, low hand or body temperature increases the risk of finger blanching because of the reduced blood circulation. It is important, therefore, that employees working outdoors in cold weather have adequate protection. The temperature in an indoor workplace should provide reasonable comfort without the need for special clothing and should normally be at least 16°C. If this is not reasonably practicable, they should be provided with warm clothing and gloves.
Gloves and other clothing should be assessed for good fit and for effectiveness in keeping the hands and body warm and dry in the working environment. Steps should be taken to ensure that what’s provided does not stop employees working safely, and does not present a risk of entanglement with moving parts of machinery. More than one set may be required for each employee if the gloves or clothing are likely to become wet.
As well as the actions that can be taken to reduce workers’ exposure to vibration, there are other measures which, while not reducing the daily vibration exposure, are thought to reduce the risk. For example:
• Plan employees’ work to avoid prolonged exposure and encourage them to take breaks during long tasks, as several shorter exposures with recovery periods are believed to be preferable to one long exposure
• Keep indoor workplaces as warm and dry as possible
• Provide screening or shelter for outdoor workers in cold, wet or windy conditions
• Provide hot drinks and warm food. This helps to maintain body temperature and is particularly important in cold working environments
• Encourage employees to take regular? exercise to help good circulation, and to exercise and massage the fingers during breaks from work with vibrating equipment
• Encourage employees to stop or cut down smoking, which can lead to impairment of circulation
To assess the anti-vibration qualities of a glove it is important to measure the vibration simultaneously at the surface of the handle and between the hand and glove e.g. inside the glove. Without this the results could be misleading due to changes in magnitudes, contact forces and the position of the transducer. Additionally, the use of an adaptor in the palm of the hand could introduce resonance complications, thereby further complicating the results.
While some gloves marketed as anti-vibration gloves achieve the criteria specified in product standard BS EN 10819:1996, there is no requirement in that standard for the vibration attenuating performance of the glove to be provided when used with a manufacturer’s products. And herein lies one of the dangers.
The PPE at Work Regulations 1992 require an employer to assess and select PPE according to its suitability. For vibration, as with any other risk, the employer must ensure that the PPE is suitable to protect against the vibration risk. They must do this by comparing the character of the risk with the characteristics of the PPE and taking account of any risks the PPE itself may cause. As a result, HSE has recommended against providing anti-vibration gloves for attenuation of hand-arm vibration, unless the gloves have been shown to achieve vibration attenuation in the actual circumstances of use.
HSE’s attempts to make triaxial measurements of the performance of anti-vibration gloves on the handles of real machines showed that it was not possible to make a satisfactory reference measurement, e.g. to get agreement between simultaneous measurements on the handle and at the palm of the bare hand. The conclusion is, therefore, that any data obtained by using an adaptor for triaxial evaluation of gloves on real machines should be regarded with great caution.
Before contemplating the use of anti-vibration gloves though, the points in the following checklist should be considered first:
• List the tools which still contribute significantly to vibration exposure (after all other reasonably practicable control measures have been taken)
• Estimate how much lower the vibration magnitudes have to be before the exposures are reduced to below the exposure action value
• Ask the supplier about glove performance in relation to these requirements
• Examine glove test data (seek help in interpreting it, if necessary)
• Check with the supplier that their gloves are suitable for the tools used
• Check whether the gloves are acceptable to employees
• Check that employees can maintain the necessary levels of dexterity when wearing the gloves
• Confirm the gloves adequately protect employees from other risks – such as cuts and abrasions or exposure to chemicals
• Check how long they are expected to last in normal use and the cost of regular replacement
One further note of caution though, especially for those engaged in piecework or payment-by-results schemes. Not only is the period of exposure likely to be intensive and with fewer breaks, but also the rapid pace of work can result in employees applying higher levels of force to the task, increasing the risk of vibration-related ill health and musculoskeletal problems.
To summarise, the vibration attenuating performance of any glove is probably heavily dependent on the main operating frequency of the tool with which the glove will be used, as well as the individual operator and the grip and feed force which will be applied by the operator during its use. So, for the time being it would be necessary to make individual assessments of the properties and performance of a glove for each tool and operator combination to meet the requirements of the PPE at Work Regulations 1992, and even this level of assessment could be subject to considerable uncertainty.
So, probably not what you wanted to hear but we can’t defy physics. The bottom line is that gloves cannot be relied upon to reduce an operator’s exposure to vibration, even when the vibration characteristics of the tool are known. While unwelcome news to some, it sort of makes it exciting and welcome in a perverse kind of way. Exciting and welcome in the sense that scientists and engineers will continue with their innovative endeavours to improve the efficiency and effectiveness of our machines and tools while working on a type of glove that fits the bill. Just look at what’s happened in the last decade. Who knows what will happen in the next.
Colin Chatten, Senior Policy Adviser, HSE. Colin’s background is one of law enforcement having spent 25 years working for Customs & Excise in a variety of roles. Towards the end of his tenure in Customs he worked closely with the Inland Revenue to help pave the way for the amalgamation of the two departments. He joined HSE’s Workplace Transport Team during the autumn of 2002 where he collaborated with the likes of the Transport Research Laboratory, the National Engineering Laboratory, insurers, trade associations, academics, trade unions and many others to help develop the Transport Route Map.
In January 2008 he transferred to the Noise and Vibration Unit where he is helping to implement HSE’s new strategy – “Be part of the solution.”
Published: 10th Jul 2010 in Health and Safety International