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Hand-Arm Vibration
All hand held power tools vibrate to some extent, and this vibration is transmitted to the operator via the
handle, or hand used to steady the tool. Vibration from about 2 to 1500 herz is potentially damaging and is
most hazardous in the range from about 5 to 20 herz.
Operators who are regularly exposed to vibration may suffer from Hand Arm Vibration Syndrome (HAVS),
which includes 'dead hand', 'dead finger', and 'white finger'. These are painful conditions and are widespread
in industries where vibrating tools are used.
The health risk depends upon the vibration level and the length of time of exposure to it......in effect, a daily
vibration dose.
Tools are tested using specialised equipment, to approximate the vibration level generated under normal,
acceptable operating conditions for the tool in question. For example, a grinder used at 45° on mild steel plate,
or a sander on softwood in a horizontal plane etc.
These tests produce a figure expressed in metres per second, which represents the vibration level, and which
appears in the specification panel of the Operating and Maintenance instruction manual.
It should be noted that if a tool is used under abnormal, or unusual conditions, then the vibration level could
possibly increase significantly. Users must always take this into account and make their own risk assessment.
Values in excess of 2.5 m/s are considered hazardous when used for prolonged periods. A tool with a
vibration value of 2.8 m/s may be used for up to 8 hours (cumulative) per day, whereas a tool with a value of
11.2 m/s may be used for ½ hour per day only.
The graph below shows the vibration value against the maximum usable time it may be used, per day.
Some tools with a high vibration value, such as impact wrenches, are generally used for a few seconds at a
time, therefore the cumulative time may only be in the order of a few minutes per day. Nevertheless, the
cumulative effect, particularly when added to that of other hand held power tools that may be used, must
always be taken into account.
Employers are advised to refer to the HSE publication "Guide for Employers".
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