What are A(8), the exposure action value and the exposure limit value for hand-arm vibration?

A(8) is a worker's daily vibration exposure expressed as the constant vibration level that would give the same energy over an 8-hour day, in m/s². For hand-arm vibration the exposure action value (EAV) is 2.5 m/s² A(8), which HSE counts as 100 exposure points, and the exposure limit value (ELV) is 5 m/s² A(8), or 400 points. Above the EAV the employer must act to reduce exposure; the ELV must not be exceeded.

How A(8) is calculated

For one tool, A(8) = a × √(T / 8 h), where a is the tool's vibration magnitude in m/s² and T is the daily trigger time. Because the time is under a square root, halving the vibration magnitude cuts exposure far more than halving the time.

With several tools, each tool's partial exposure is combined into one daily value, which is why HSE's points system is convenient: points simply add up. Our exposure calculator does both for every tool your team uses.

Where the values come from

In Great Britain the values are set by regulation 4 of the Control of Vibration at Work Regulations 2005. They implement EU Directive 2002/44/EC, which sets the same 2.5 and 5 m/s² values for every EU member state. In Sweden they are in AFS 2023:10.

From estimate to measurement

A calculation uses a tool's declared or measured magnitude. The HAVS Protect sensor measures the vibration that actually reaches the worker's hand and turns it into the same points scale, with a lamp that goes yellow above 100 points and red at 400.

Frequently asked questions

How many points is the exposure action value?
100 points per day, equal to 2.5 m/s² A(8).
How many points is the exposure limit value?
400 points per day, equal to 5 m/s² A(8).
What does the 8 in A(8) mean?
It is the 8-hour reference period: exposure over the actual working day is normalised to an equivalent 8-hour day.

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