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In recent times we have no doubt all become very familiar with the term PPE (Personal Protective Equipment). For hazardous agents in the workplace, PPE is the last line of defence, to be resorted to only when all other efforts to control the hazard have resulted in there still being a level of risk that needs to be managed.
Antivibration gloves can be legitimately sold, even in the United Kingdom (UK) and the EU, as PPE for protection against exposure to hand-arm vibration. The unsuspecting purchaser or potential user could therefore be forgiven for thinking that if they have purchased a glove described as ‘antivibration’ and bearing a CE mark or UKCA mark, there is a guarantee that the glove will provide effective protection against vibration. Yet the Health and Safety Executive (HSE; the British Regulator), in its guidance to the Control of Vibration at Work Regulations 2005 (which implemented the EU Vibration Directive in the UK), advises employers that antivibration gloves cannot be relied upon to provide protection from vibration. So, what should employers think? This article outlines some of the reasons why, in most situations, antivibration gloves are not effective and should not be relied upon to provide any benefit to the wearer; in fact, their use may cause more harm than good.
In compensation claims for vibration[1]related personal injury (Hand-Arm Vibration Syndrome), it is common, in my experience, for claimants to allege that the defendant employer was negligent in that it did not provide antivibration gloves. Given HSE guidance, however, an employer should not be criticised for not supplying gloves as PPE against vibration. Some defendants cite gloves as a control measure, and this might suggest other problems. For example, an employer relying on gloves and believing the problem of vibration has been solved may well neglect to look at those control measures that could, and should, be employed to reduce vibration exposure and risk.
HAV assessment
To understand the issues associated with the assessment of an antivibration glove, it is first necessary to understand how I exposure to hand-arm vibration is assessed. The current internationally accepted method for assessing an individual’s exposure to hand-arm vibration is standardised in ISO 5349- 1:2001. The method combines information on the duration of the exposure and the frequency-weighted vibration magnitude to produce a daily vibration exposure value. Specifically, the vibration magnitude to which an individual is exposed, is measured at or near the gripping zone of a power tool, in terms of the root-mean-square acceleration in the three orthogonal directions. The measured acceleration is weighted using the frequency weighting defined in the standard (ISO 5349- 1:2001). The daily exposure duration can be evaluated by direct observation, video recording, or work piece counting. Then, the frequency-weighted acceleration and daily exposure duration are combined to calculate the daily vibration exposure.
“this article outlines some of the reasons why, in most situations, antivibration gloves are not effective”
Glove testing
In the current standard test for an antivibration glove (ISO 10819:2013+A1:2019) the vibration transmitted through the glove to the wearer is tested in compression at the palm of the hand. The amount of vibration transmitted through the glove in a single direction is measured and the results are used to calculate the vibration transmission in two ranges of frequencies, both of which must be sufficiently low for the glove to bear the CE or UKCA mark and be sold as an antivibration glove in Europe.
Without going into technical details regarding the test, the approach for assessing an antivibration glove raises a number of wider issues. The first is that for an operator using a power tool, vibration is likely to be transmitted to all areas of the hand in contact with the vibrating surface, not just the palm. Research has shown not only that the gloved hand responds differently to vibration at the fingers compared with at the palm, but also that, rather than reducing vibration, a glove often amplifies vibration at the fingertips. In some circumstances, vibration may also be amplified at some frequencies at the palm of the hand. Furthermore, the transmission to, and dynamic response of, the hand-arm system is different if the glove material is tested in shear, i.e., with the vibration running parallel to the glove surface through a gripped hand. But the shear direction is not considered at all in the test, even though the standard method for assessment of vibration exposure (ISO 5349-1:2001) considers the vibration in all directions.
When a glove is used, factors such as the physical characteristics of the wearer, their different postures and varying grip and push forces will affect how much vibration is transmitted through the glove material. The transmission can be very different for different types of power tool, depending on factors such as the speed of rotation of rotary tools such as grinders, or the number of impacts per second for impulsive tools such as demolition hammers. These factors affect the main frequencies of the vibration coming from the tool and they can change depending on how the tool is used. In general, an antivibration glove is more likely to reduce vibration transmission at higher frequencies than at lower frequencies. The many variables affecting how a glove responds mean that it is practically impossible to predict how a glove will perform, and in any case its behaviour will be constantly changing under conditions of use, but this also means that there may be conditions under which the glove amplifies, rather than reduces, the vibration.
Glove material properties
The performance of a glove in terms of its ability to reduce transmission of vibration at lower frequencies is proportional to thickness and inversely proportional to the stiffness. However, practical considerations tend to limit the thickness of the glove. For example, a thicker glove may affect manual dexterity and this may have safety implications. A thicker glove may also mean that the wearer has to exert more force to be able to carry out the usual work and this may in turn lead to increased fatigue.
It is easy to criticise the current standard test for an antivibration glove. However, it is important to acknowledge the difficulty associated with development of such a test. The techniques that must be applied to make an adequate assessment of glove performance are complicated and costly, and the benefits of specifying a more thorough test are largely outweighed by the lack of any discernible benefits of wearing an antivibration glove. Consequently, further improvement of the test of glove transmissibility may be unlikely.
The most recent version of the standard test for an antivibration glove contains normative Annex B, added in 2019, which includes requirements to make it clear that gloves are, for the most part, unlikely to provide any real protection against vibration. Paragraph B.2 b) requires that the information supplied by the manufacturer of the glove shall include:
“a warning that the use of a protective glove does not imply a sufficient protection against health risks due to vibration or other factors. In addition, the measured vibration attenuation results cannot be used to calculate daily vibration exposure values within a risk assessment, e.g. according to ISO 5349-1”.
This requirement makes it clear that the glove should not be relied upon to protect the wearer and that data from the test cannot be used to estimate a ‘protected level’ in the way that, for example, attenuation data for hearing protectors can be used.
Legal requirements
In terms of legal requirements, the EU Vibration Directive does not specifically mention antivibration gloves. The only mention of PPE is a reference to the provision of clothing to protect against cold and damp. In the UK, the Personal Protective Equipment at Work Regulations 1992 require that the employer assesses and selects PPE according to its suitability. The employer must do this by comparing the characteristics of the risk with the characteristics of the PPE and take into account any risks the PPE itself may cause. The standard test in ISO 10819:2013 does not provide any direct information that can be used to estimate the protection that a glove may provide to the wearer. In addition, there are many uncertainties in the test results.
Currently, there are no other standards for estimating the protection afforded by antivibration gloves when using vibrating machinery. This makes compliance with the PPE at Work Regulations very difficult (arguably impossible) to achieve with respect to antivibration gloves, and also makes it very difficult to produce evidence, one way or another, about the effects that a glove has on the vibration exposure of an individual. So, while the supply side law allows the marketing and sale of antivibration gloves, the workplace law requires that their suitability is assessed and, at present, any reasonable assessment would not only be difficult to achieve but could only conclude that they were not suitable.
ISO 10819
ISO 10819 assesses the performance of antivibration gloves. There is also a standard for measuring the performance of resilient materials used for antivibration gloves: ISO 13753:2008, which superseded ISO 13753:1999. Studies have been reported that investigated the properties of different materials using this test and have shown that in this test, resilient materials tend to produce amplification between 10 and 31.5 Hz. The revised 2013 standard test for antivibration gloves does not consider the performance of a glove below 25 Hz. It seems a serious omission to ignore the performance of a glove at the frequencies that are given the most weight by the hand-arm frequency weighting, particularly when there is evidence from the materials test that there may be amplification at these frequencies.
Antivibration efficacy
A further consideration with regard to techniques for estimating the effectiveness of antivibration gloves is the averaging of transmissibilities to represent the performance of a glove for the entire population. In the particular case of antivibration gloves, the inter[1]subject variability can be very large. As an example, data from research on one glove type showed that for a tool with a dominant vibration frequency at around 160 Hz, the difference in y-axis (through the closed hand, see illustration) performance could range from 36% reduction to 79% amplification in vibration magnitude. This could mean that a glove and tool combination that appears to have the potential to provide protection for one tool operator could actually cause considerable amplification for another. Use of averaging techniques is intended to provide an adequate safety margin to take individual variability into account. However, without assessment on an individual basis, it would not be possible to identify which operator, glove, and tool combinations might actually result in increased exposures. Also, the frequency spectrum for a given power tool is not always constant. Variability in the spectral shape with different applications, caused, for example, by unmonitored changes in operating air pressure of pneumatic tools, can occur. Any such changes in frequency content of the vibration from the tool could also influence the effectiveness of a glove in some circumstances.
Durability
Durability is also important for antivibration gloves. Resilient materials that are constantly compressed when in use may eventually remain partially compressed, losing much of their vibration attenuation performance. Some antivibration gloves also incorporate a material made of several connected air pockets, where the effect of puncturing would no doubt reduce performance. As with most aspects of PPE, the effect of wear and tear is only likely to have a detrimental effect on the potential to provide adequate protection.
As a result of the multitude of issues surrounding their assessment and performance, some of which are described above, and also because there is a lack of scientific evidence to show that antivibration gloves can significantly reduce the risk of vibration exposure, the simplest advice, as given by HSE, is that gloves cannot be relied upon to provide any benefit, and that they may in some situations, have the opposite effect. Gloves can, of course, be used to keep the wearer’s hands warm and dry, which is beneficial for maintaining good circulation, and gloves are also used in many applications to protect against other hazards such as cuts and burns, but antivibration gloves may not be the most suitable gloves for this purpose.
Other means of controlling exposure to vibration, such as eliminating the vibration altogether using alternative work techniques, buying and using low[1]vibration machinery, carrying out routine preventative maintenance and controlling exposure durations, are far more likely to reduce vibration exposures and should all be considered and or implemented, rather than resorting to antivibration gloves. When managing hand-arm vibration risks in the workplace, the correct approach is to follow a structured process that, if followed correctly, will in most cases mean that purchase of antivibration gloves is not even considered. The following are some top tips for managing hand-arm vibration.
Top tips for managing hand-arm vibration
- Understand the risks: Know where there are risks from vibration in the business, and why (what job roles or types of work involve significant risk, and what work equipment is involved) and identify priority areas for action.
- Meet the legal limits: Make sure no employee is exposed above the legal limit for hand-arm vibration.
- Eliminate and reduce: Put steps in place or develop a plan to make sure vibration exposure is eliminated or reduced where necessary (even if the legal limit is not exceeded). For example, design out the problem; if not possible then do the work a different way; select better vibrating tools where their use is unavoidable and maintain the tools.
- Review: Put a system in place to identify new or emerging vibration risks in your business and new solutions or good practices. Are your practices on elimination or reduction of exposure under review as technology and good practice in your industry changes? Do you ensure that systems and working methods are followed in practice?
- Train employees: Employees should be trained in your systems of work, proper use of tools and machines, and the signs and symptoms of vibration related disease.
- Don’t needlessly monitor exposure: Continuous monitoring or recording of vibration exposure, whether with paper systems or electronic devices, is not a legal requirement and is generally not helpful
- Check employees’ health: Provide appropriate health surveillance for people at risk of vibration-related disease. Your system should include details of how you will manage any ill health in employees.
- There is no effective PPE: No glove can be relied upon to reduce vibration exposure.
For more details regarding the issues raised in this article, please read my commentary from 2015, co-authored with experts from National Institute for Occupational Safety and Health (NIOSH) and published online.
