Hand-Arm Vibration

From the tool to the hands

In drilling and grinding work, vibration assessment concerns the hands holding the operating tool. In Great Britain, the Health and Safety Executive (HSE) links regular work with hand-held or hand-guided power tools for more than a few hours each day with a risk of damage to nerves, blood vessels and joints in the hand, wrist and arm, in its guidance on vibration and the hands. HSE calls the condition caused by exposure to vibration at work hand-arm vibration syndrome, usually shortened to HAVS. It describes HAVS as preventable, while stating that damage, once done, is permanent.

For drilling and abrasive work, the practical subjects covered by the authorities include the time the hands are in contact with operating equipment, the condition of that equipment and the force used to grip it. Those subjects connect the work process with what reaches the hands.

Sensation, circulation and hand function

HSE's listed warning signs include tingling and numbness in the fingers, which can disturb sleep, and difficulty feeling things with the fingers. It also lists a loss of strength in the hands, with less ability to pick up or hold heavy objects. In cold and wet conditions, its account describes fingertips going white, then red, with pain as they recover. These are warning signs described by the source, rather than a diagnosis for an individual workshop user.

The UK Industrial Injuries Advisory Council (IIAC), in its report on hand-arm vibration and exposure assessment, describes Raynaud’s phenomenon as episodes of finger blanching caused by a temporary interruption of blood flow to the ends of the fingers. During an episode, it describes the affected part as cold, numb and marble white or blue. Cold typically triggers the episodes, and the affected parts become fiery red and tingle as circulation returns during recovery, according to the Council.

Trigger time and daily exposure

HSE's vibration risk-assessment guidance asks employers to observe how long employees are actually exposed to vibration. Its description of total daily 'trigger time' is the time with the equipment operating and in contact with the employee's hands. The two conditions belong together in that description: the equipment is operating, and the hand is in contact with it.

Where a typical day involves more than one tool or work process, HSE calls for information on the likely vibration level and trigger time for each one. For a day split between drilling and grinding, for example, that approach means considering the likely level and contact time for each process. HSE's requested information therefore describes both the vibration associated with a task and how long the hands are exposed to it.

Change the work and maintain the equipment

In its guidance on protecting workers from hand-arm vibration, HSE starts with alternative work methods that eliminate or reduce exposure. For tool selection, it recommends the lowest-vibration tool that is suitable for the work and can do it efficiently. Both suitability for the task and efficient working are part of that recommendation. HSE also calls for appropriate maintenance programmes to prevent avoidable increases in vibration, following the manufacturer's recommendations where appropriate. HSE identifies trade associations, other industry contacts, equipment suppliers and trade journals as possible sources of information about good practice in an industry.

Consumable condition is part of that account: HSE says blunt or damaged concrete-breaker and chipping-hammer chisels should not be used. It also identifies replacement of consumables such as grinding wheels, so that equipment remains efficient and employee exposure is kept as short as possible. For the organisation of work, HSE recommends limiting exposure time and avoiding long, continuous periods, with several shorter periods preferable.

In Canada, the Canadian Centre for Occupational Health and Safety (CCOHS) explains in its guidance on vibration measurement and control that grip force affects how much vibrational energy enters the hands. It recommends the lightest grip that still allows safe operation of the tool or process. It also recommends sufficient clothing, including gloves, to keep warm. CCOHS also recommends rest periods to avoid continuous exposure and resting the tool on the workpiece whenever practical. Its guidance says to maintain tools properly and avoid faulty tools, noting that worn, blunt or misaligned tools vibrate more.

For construction work, HSE describes eliminating the process that causes exposure, or substituting a process with less exposure, as the best ways of dealing with hand-arm vibration exposure. It places consideration of those options within risk assessment and says organisational measures such as job rotation can also be useful. Its account includes equipment selection that reduces exposure to vibration.

What gloves and exposure limits cannot promise

HSE's construction guidance on vibration distinguishes warmth from protection against tool vibration. It says normal gloves are useful for keeping hands warm in cold weather, but no gloves provide effective protection against vibration from hand-held tools. It specifically describes anti-vibration gloves as an ineffective measure against hand-arm vibration exposure. The same guidance says that restricting exposure to just below the Exposure Limit Value still results in many workers developing HAVS.

The IIAC discussion of measurement and individual variation also describes uncertainty in assessing exposure. It notes that measurements for various tools can produce a range of values affected by the ergonomics of the work, workpiece hardness and tool maintenance. When considering an approach relating exposure dose to response, the Council says variation between individuals and between workplace tasks needs to be acknowledged. The Council's account therefore includes the workpiece, the work arrangement and the state of the tool alongside differences in individual responses.

Report changes in the hands

HSE's advice on reporting hand symptoms is to report any symptoms promptly to the employer or the person carrying out health checks. Its warning signs cover changes in sensation and hand strength as well as the cold-related finger colour changes it describes. For workshop work, the source guidance brings together alternative methods, suitable equipment, maintenance, actual contact time, safe grip and prompt reporting of symptoms.