Nail guns and staplers, and upper limb disorders: not just a vibration problem
There can be a tendency to think of the occupational ill health that can arise from the use of nail guns and staplers as a vibration problem. In this article, Finch experts Tim Ward, Dr Steve Cowley and Sue Hewitt discuss why looking only at vibration is not the best approach, and describe the range of risk factors that should be addressed in dealing with the risk of upper limb disorders from the use of such tools.
The use of nail guns and staplers (and other types of fastener driving tools) in occupational settings carries a risk of upper limb disorders (ULDs). Types of work in which such tools commonly are used include furniture manufacture and upholstery, construction work, and manufacture/repair of pallets.
Risk factors for the development of ULDs include repetition (using the same muscle groups over and over); awkward or static postures; high forces, including grip force and applied force; duration of the task; and vibration exposure.
Risk factors for ULDs commonly interact with each other, and generally, there is an increased risk of injury when a number of risk factors come together in a given job or task. Employers therefore should address the range of possible risk factors in seeking to avoid workers developing ULDs. To put it another way, it would be wrong to assume that one particular risk factor is the most or only significant one to tackle.
Vibration is a case in point when it comes to nail guns and staplers. A nail gun transmits energy into the operator’s hand and arms, in the form of isolated short-duration shocks. This can be called vibration, although it is different to the type of vibration experienced from the use of a grinder, chainsaw or demolition hammer. Whether this type of shock vibration can be linked to the vascular (finger blanching) or neurological (numbness and tingling) components of hand-arm vibration syndrome (HAVS) remains uncertain. Even for ‘conventional’ vibration, the epidemiological evidence for a link to the musculoskeletal disorder of carpal tunnel syndrome (CTS) is generally considered to be weak (most likely due to difficulty in separating the possible risk factors at the point of diagnosis).
It is also uncertain if measured vibration magnitudes on nail guns, and vibration exposures, can be relied upon to indicate the risk of developing an ULD such as CTS or HAVS. So, whilst a daily vibration exposure (the A(8) value) may be estimated for use of a nail gun, arguably it would not be meaningful to compare (as an indicator of risk) this with thresholds such as the 2.5 m/s2 A(8) Exposure Action Value of the Control of Vibration at Work Regulations 2005.
Nevertheless, reducing the vibration exposure in work with nail guns and staplers will likely contribute to a reduction in the risk of ULDs.
The measurement of vibration on nail guns and similar can be difficult due to the tendency for the impulsive signal to overload the measuring instrumentation – special care and expertise in measurement is recommended.
It is also not straightforward to use measured vibration values to estimate a daily vibration exposure (the A(8) value). For example, consider vibration measured on a nail gun over a period of 2 minutes, during which 24 nails were fired. Only if the same rate of nail use (12 per minute) is applied to the total duration of tool use in the working day, could this sample measurement be used directly, with the daily duration of use, to give a daily vibration exposure. Otherwise, a correction would have to be applied, either based on the actual rate of use or on the number of nails used per day – the latter probably being the easier method, since most well-run businesses will know how many nails, staples, etcetera, are used in a day, month, product or task.
The same issue will arise with tool manufacturers’ declared vibration emission values for nail guns; the vibration emission test codes in ISO 8662-11:1999+A1:2001 and the draft BS EN ISO 28927-13 provide a vibration figure for a firing rate of 10 shots per 30 seconds.
For fastener driving tools such as nail guns, the best use for manufacturers’ data is to compare tools in order to select the most suitable one, on the basis that a lower vibration magnitude is better. HSE research report RR591, published in 2007, found that purely in terms of vibration, there was little to choose between tools of the same type on the market. Any tools on the market with a significantly higher vibration than the rest should therefore easily be identified and avoided. Equally, avoid tools for which there is no vibration information.
What would an employer be expected to do to manage the risk of ULDs from the use of nail guns and other fastener driving tools?
So, what would an employer be expected to do to manage the risk of ULDs from the use of nail guns and other fastener driving tools? The risk factors might well be addressed along the following lines:
- Elimination – can (parts of) the work be done without using a nail gun/stapler/etcetera; is there a different (lower risk) way of achieving the fixing;
- Reduction – could fewer fastenings be used per piece; reducing the number could assist with the risk factors of repetition, duration, and vibration exposure;
- Suitable equipment – if fastener driving tools have to be used, choose the most suitable – look for good ergonomic design, considering tool weight and balance, vibration (see above), impact energy and recoil, design of handles for optimal gripping force;
- Workstation design – can the working area be adapted to avoid awkward work postures and hand/wrist/arm positions;
- Auxiliary equipment – can the tool be supported such as in a balancer or tensioner, allowing reduced applied force and grip force; can the position of the workpiece be adjusted to allow a good working posture, such as with simple trestles or more sophisticated manipulators.
Equally, employers should consider the above in relation to non-power tool risk factors for ULDs – for example, to address manually applied forces, pinch or power grips, postures and repetition.
There is no specific health and safety legislation dealing with upper limb disorders (ULDs). In addition to the Health and Safety at Work etc. Act 1974, a range of secondary legislation may be relevant, such as the Management of Health and Safety at Work Regulations 1999, Provision and Use of Work Equipment Regulations 1998, Manual Handling Operations Regulations 1992, and Control of Vibration at Work Regulations 2005. However, readers may wish to note that it would be wrong to invoke or apply the Manual Handling Operations Regulations to risks arising from the use of power tools (carrying a heavy or awkward tool at work might be classed as a manual handling operation; using the tool for its intended purpose is not).
HSE guidance on ULDs includes the brief guide INDG171 Managing upper limb disorders in the workplace (https://www.hse.gov.uk/pubns/indg171.pdf), and the comprehensive guidance HSG60 Upper limb disorders in the workplace (https://www.hse.gov.uk/pubns/priced/hsg60.pdf). There is also the ‘ART’ (assessment of repetitive tasks) tool described in INDG438 (https://www.hse.gov.uk/pubns/indg438.pdf). All will assist employers in ensuring that the various risk factors, including vibration, are assessed.
The use of fastener driving tools, such as nail guns and staplers, carries a risk of upper limb disorders (ULDs). Risk factors for ULDs generally include vibration where there is the use of power tools. However, with nail guns and other fastener driving tools, vibration is just one of a number of risk factors that should be tackled and is not necessarily the most significant. Employers should address the range of possible risk factors in seeking to avoid workers developing ULDs, such as carpal tunnel syndrome (CTS).
To subscribe to the Finch newsletter please click here.
 HSE, Upper Limb Disorders, http://www.hse.gov.uk/msd/uld/index.htm
 HSE, Correlation between vibration emission and vibration during real use: Fastener driving tools, RR591 (2007), www.hse.gov.uk/research/rrpdf/rr591.pdf