The Definition of Vibration Exposure

Definition of Vibration Exposure

Vibration exposure is the amount of mechanical vibration that passes into a worker's body from tools, machinery or vehicles during the workday. It is measured as the strength of the vibration, expressed as acceleration in meters per second squared (m/s²), combined with how long the worker is exposed to it.

Occupational vibration is divided into two types. Hand-arm vibration (HAV) enters through the hands from powered hand tools, hand-guided machines or workpieces held against a machine. Whole-body vibration (WBV) enters through the seat or feet, usually from driving or riding in vehicles and mobile machinery over rough ground.

Regular, long-term exposure can cause permanent harm. Hand-arm vibration can lead to hand-arm vibration syndrome, including vibration white finger, and has been linked to carpal tunnel syndrome. Whole-body vibration is associated with low back pain and other back problems, especially when combined with poor posture and long periods of sitting.

How Vibration Exposure Is Measured and Limited

Measurement standards

• ISO 5349: the international standard for measuring and evaluating hand-arm vibration. It combines vibration in three directions into a single frequency-weighted value.
• ISO 2631-1: the international standard for evaluating whole-body vibration in relation to health and comfort.
• ACGIH: the American Conference of Governmental Industrial Hygienists publishes threshold limit values (TLVs) for both hand-arm and whole-body vibration that draw on these ISO methods.

Daily exposure, A(8)

Daily exposure is normally expressed as A(8), the vibration level averaged over a standard 8-hour day, similar to a time-weighted average for noise or chemicals. Because the calculation uses the square root of time, halving the vibration level allows four times as much use. For example, a breaker that vibrates at 5 m/s² used for 2 hours gives an A(8) of 2.5 m/s².

European and UK values

EU Directive 2002/44/EC sets the following daily values, normalized to an 8-hour reference period:

• Hand-arm vibration: exposure action value of 2.5 m/s² and exposure limit value of 5 m/s².
• Whole-body vibration: exposure action value of 0.5 m/s² and exposure limit value of 1.15 m/s². Member states may instead use vibration dose values (VDV) of 9.1 m/s^1.75 for action and 21 m/s^1.75 as the limit.

Great Britain applies the same A(8) values through the Control of Vibration at Work Regulations 2005 (SI 2005/1093). Above the action value, employers must put in place a program of technical and organizational measures to reduce exposure. The limit value must not be exceeded. HSE also publishes an exposure points system, where 100 points equals the hand-arm action value and 400 points equals the limit value.

United States

OSHA has no specific standard for occupational vibration. US employers typically use the ACGIH TLVs and ISO methods to assess exposure, and NIOSH has published a criteria document on hand-arm vibration with recommendations for reducing exposure and monitoring workers' health.

Common Sources of Vibration Exposure

Hand-arm vibration

• Breakers, jackhammers and rotary hammers. See jackhammer safety.
• Angle grinders, sanders and polishers.
• Chainsaws, hedge trimmers and brush cutters.
• Impact wrenches, needle scalers, chipping hammers and riveting tools.
• Compactors and plate compactors.
• Pedestal grinders, where the worker holds the workpiece.

Whole-body vibration

• Earthmoving equipment, such as dozers, loaders and dumpers.
• Agricultural tractors and quad bikes.
• Forklifts and other industrial trucks driven over uneven surfaces.
• Off-road and heavy goods vehicles on poor roads.

Controlling Vibration Exposure

Controls should follow the hierarchy of controls, starting with eliminating the vibrating task where possible.

Practical steps

• Assess the risk: identify which tasks and tools expose workers, estimate daily exposure using manufacturer data or measurements, and record the results in the risk assessment.
• Change the method: for example, use a mounted breaker on an excavator instead of a hand-held breaker, or design out drilling and scabbling.
• Choose low-vibration equipment: include vibration emission data in purchasing decisions.
• Maintain tools and machines: worn bits, unbalanced parts and blunt chisels increase vibration. Build checks into preventive maintenance.
• Limit exposure time: use rotation and time limits so workers stay below the action value where possible.
• Improve seats and routes: use suspension seats suited to the vehicle, maintain haul roads and adjust speed to ground conditions.
• Keep workers warm and dry: cold reduces blood flow to the fingers and can trigger symptoms.
• Train workers: explain the risks, how to use tools with a lighter grip and how to report symptoms early.
• Provide health surveillance: where workers remain at risk, set up medical surveillance to detect early signs of harm.

Example of Vibration Exposure

A utilities contractor's crews used hand-held breakers to open road surfaces several hours a day. A vibration assessment using the tool's measured vibration level showed that some workers were exceeding the hand-arm limit value of 5 m/s² A(8) on busy days.

The contractor switched to excavator-mounted breakers for larger openings, bought lower-vibration breakers for small jobs and set daily trigger times for each tool. Supervisors rotated tasks so no one exceeded the action value without a review. Workers were trained to report tingling or finger blanching, and a health surveillance program was started for everyone who still used vibrating tools regularly.

Frequently Asked Questions: Vibration Exposure

What is the difference between hand-arm and whole-body vibration?

Hand-arm vibration enters through the hands from tools or workpieces and mainly affects the blood vessels, nerves and joints of the hands and arms. Whole-body vibration enters through the seat or feet, usually in vehicles, and is mainly linked to back pain.

Does OSHA have a vibration exposure limit?

No. OSHA has no specific vibration standard. Employers in the US commonly use ACGIH TLVs, ISO methods and NIOSH guidance to assess and control exposure.

What are the vibration action and limit values in the UK and EU?

For hand-arm vibration, the daily action value is 2.5 m/s² A(8) and the limit value is 5 m/s² A(8). For whole-body vibration, they are 0.5 m/s² A(8) and 1.15 m/s² A(8).

Do anti-vibration gloves solve the problem?

Not on their own. Gloves can help keep hands warm and dry, but their ability to reduce vibration varies and is often limited at the frequencies most tools produce. Equipment selection, work methods and time limits are more reliable controls.

How do I know how much vibration a tool produces?

Start with the manufacturer's declared vibration emission value, then check it against real-world data or measurements, since tools often vibrate more in use than in standardized tests.