The European standard EN 12464-1 highlights the minimum illuminance requirements of an actual working area rather than the entire room. The guidelines recommend that the lighting outside the working area should be adapted to the conditions that apply inside the working area. The values stated in the collection of tables, refer to the lowest illuminances in the workspace of a visual object, that can be either horizontal, vertical or placed at an angle.
The illuminances documented consider the lowest average values for working under normal conditions. However, the illuminances can be adjusted by the increments set out below if the visual conditions deviate from the normal conditions.
The demands on illuminances used in the workplace, should be regularly reviewed to overcome the following situations; difficult working conditions, activities that demand great accuracy or high productivity, impairment of visual efficiency, viewing objects with fine detail or in low contrasts of light or the use of DSE terminals for long periods of time.
In practice, the specified illumination can be reduced under the following conditions; when visual objects have an abnormally large size and high contrast or when visual work is in progress for short periods. In workplaces with continuous occupancy the illuminance must not drop below 200 lx. Continuous occupancy refers to work that is performed for more than two hours.
The recommended values assume that the employees have normal sight. If a greater number of people have some form of sight impairment, this should be taken into consideration when designing a lighting installation.
Lighting the visual object
The main principle is that the light falls in such a manner that the greatest possible contrast is placed on the visual object, which may have a horizontal, vertical or sloping position. It can also consist of varied structures or have different combinations of surface characteristics, matt, bright etc,resulting in varied reflective characteristics.
A basic prerequisite for good visual comfort in the workplace, is that the work object’s position and shape, in relation to the direction of light, does not cause any form of unpleasant glare or glare that impairs the vision e.g. dazzling luminaires or disturbing reflections.