The most common error in the assessment of the exposure of workers to vibration is related to the assigned exposure times.
In the case of hand-arm must count the time when the worker is exposed to vibration; one should not count on a period in which a worker has landed the equipment or that is holding it without being in operation. The contact time is the time during which the hands are effectively exposed to vibration from the tool or workpiece. Often, This period is much lower than the ' working time ' and is usually overrated by operators.
In the situation of whole-body, When questioned about the usual daily duration of exposure, the operators of machines or vehicles indicate generally a value which includes periods without exposure, as for example the truck load times and waiting. Usually, the vibration of a vehicle in circulation has a preponderant role in exposure. However, some exhibitions verificam‑se especially in operations performed while the vehicle is stopped, as in the case of excavators and forestry mowers.