Abschnitt 3.3 - 3.3 Office and VDU work
3.3.1 Room design
Do your employees frequently comment on a lack of space? Are the circulation and escape routes wide enough for escape to safety to be possible without difficulty in the event of a fire? Areas of sufficient size are essential in order for your employees to be able to work ergonomically and efficiently. This chapter provides information on the use of space.
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Your employees face the following hazards in constrained spaces:
Collision with furnishings
Tripping and falling owing to constrained circulation routes and materials left in the areas
Critical situations in an emergency owing to bottlenecks, obstructed circulation routes and unusable escape routes
Health complaints owing to unergonomic workstation arrangements
A sense of nuisance, harassment or intimidation owing to violation of the personal space
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In order for the hazards described above to be avoided in your offices, the following guideline values have been laid down for VDU and office workplaces:
8 - 10 m2 per person,
12 - 15 m2 in large open-plan offices (i.e. with a floor area > 400 m2).
These surface areas comprise the following discrete areas (Figure 7):
Work surface (desk surface) of at least 1,600 mm × 800 mm (width × depth) (where the need for work equipment is low, the width may be reduced to 1,200 mm; see Chapter 3.3.2)
Free movement area at the workstation at least 1.5 m2 (width and depth at least 1 m)
Utility areas for further office furniture, office equipment (printers, photocopiers, fax machines) and for other materials needed (e.g. product samples)
Functional areas for the moving parts of furniture, machinery, equipment and furnishings
Free user areas for persons at furniture, machinery, equipment and furnishings: depth at least 800 mm; for functional areas on furniture, machinery, equipment and furnishings (e.g. cupboard with pull-out element), an additional safety clearance of 500 mm
Adequately wide circulation routes (Table 6)
Plan additional areas for use as break and discussion areas. Pay attention to accessible design; this may necessitate larger areas.
Functional areas with adequate dimensions must be provided for windows and doors. Ensure that during use, no pinch, shear or collision points arise in conjunction with other parts of the building or other furnishings (for example: safety clearance to the body of at least 500 mm).
Ensure that free user areas at workstations are not obstructed or overlapped. The functional areas of cabinets used only at the workstation concerned may overlap its free user area.
When positioning desks, ensure that the user's line of sight is parallel to the glazed wall (Figure 9). This helps to prevent daylight from causing disturbing glare and reflections on the VDU (see Chapter 3.2.1).
Figure 7 Areas at an office workstation
Figure 8 Example of permissible overlap of areas
Circulation and escape routes
Ensure that circulation routes are sufficiently wide (see Table 6) and that they are not constrained by the moving parts of work equipment.
Ensure that escape routes are kept clear at all times.
Table 6 Minimum width of circulation and escape routes
Minimum width of circulation and escape routes * (determined as a function of the number of users) | ||
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Number of users * | Clear width | Possible constraints upon the clear width only at doors in corridors |
to 5 | 875 mm At no point less than 800 mm | By no more than 75 mm, i.e. minimum width 800 mm |
to 20 | 1000 mm | By no more than 150 mm |
to 200 | 1200 mm | |
to 300 | 1800 mm | |
to 400 | 2400 mm |
Figure 9 VDU arrangement
Ensure that the access to a workstation assigned to a specific individual is at least 600 mm in width and that routes to facilities used occasionally (e.g. thermostats, windows) are at least 500 mm in width.
Pay attention to accessible design; this may necessitate wider circulation routes.
Ceiling height
Ensure that the room is of adequate height. The required ceiling height of a work room is a function of its floor area (see Table 7).
During the risk assessment, you can check whether the dimension for the ceiling height can be lowered by 0.25 m if this can be considered to have no adverse effect upon your employees' health. A minimum ceiling height from the floor of 2.50 m must however be assured. In work rooms with a floor area of up to 50 m2, the ceiling height can be reduced to the dimension permitted by the regional construction legislation, provided this can be reconciled with the usage of the work rooms.
Table 7 Minimum ceiling heights
Floor area | Ceiling height of offices above floor level |
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< 50 m2 | At least 2,50 m |
> 50 m2 | At least 2,75 m |
> 100 m2 | At least 3,00 m |
> 2000 m2 | At least 3,25 m |
3.3.2 Furniture
Office furniture such as tables, chairs, cabinets and shelves constitutes important work equipment within your company. These items must be safe and functional. At the same time, they should counteract inactivity. Suitable office chairs support the natural human seating posture.
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Your employees face the following hazards:
Injuries caused by tipping or falling of furniture, pinch and shear points on moving parts, or sharp corners and edges
Electrical hazards on relevant fixtures (e.g. cabling)
Falls resulting from the office chair inadvertently rolling away
Constrained or incorrect posture resulting from ergonomically unfavourable design and adjustment of the furniture
Measures |
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Design your company's workplaces to be safe and ergonomic.
Take account of the personal needs of your employees.
Ensure that electrical equipment on your furniture is installed and regularly checked by skilled personnel.
Avoid high-gloss surfaces and pay attention to an acceptable reflectance (see Chapter 3.2.1).
Office desks
Procure desks that permit a flexible arrangement of the VDU monitor, keyboard, paper documents and other work items (adequately large work surface).
The work surface of the desk should be at least 1,600 mm wide and 800 mm deep. In exceptional cases, the width can be reduced to 1,200 mm when the workstation is equipped with only a single VDU monitor, few paper documents are used, and alternating tasks are not performed. Refer to Figure 10 for the requirements concerning height-adjustable desks.
Ensure that sufficient unobstructed legroom with a width of at least 850 mm (recommended: 1,200 mm or more) is available below the work surface.
Alternation between seated and standing tasks provides additional opportunity for movement. It is therefore advisable to use seated/standing desks that permit this alternation (adjustment range from 650 mm to 1,250 mm, Figure 10).
Office chairs
Ensure that the seat and backrest are height-adjustable and can be rotated as a single unit.
Ensure that the chair has braked castors (preventing the chair from rolling unchecked when not under load) and that the castors are suitable for the type of floor covering (Figure 11).
The majority of office chairs are designed for eight hours' use per day and a body weight of 110 kg. Use suitable chairs for heavier persons or multi-shift use.
Whenever possible, select chairs with armrests, since these are ergonomically advantageous for your employees. Armrests adjustable within a height range from 180 mm to 290 mm above the seat surface are recommended.
Figure 11 Left: castor for hard floor coverings (two-colour); right: castor for soft floor coverings (single-colour)
Table 8 Guide to the selection of ergonomically designed office chairs
Dimension | Dimension range |
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Seat height | < 400 to 530 mm |
Seat height adjustment range | > 120 mm |
Seat depth | 370 to 470 mm |
Seat width | > 450 mm |
Lumbar support | Support point adjustable in the range from 170 to 230 mm above the seat surface |
Upper edge of the backrest above the seat surface | > 450 mm |
Backrest width | > 400 mm |
Backrest angle | Adjustable, at least 15° |
Not a permanent solution. Ensure that alternative seating furniture (e.g. balance ball chairs, motion stools) are used by your employees only as temporary training and exercise furniture. Owing to the elevated risk of accident, rapid muscle fatigue and absence of adjustments, these items of furniture are not suitable for use as office chairs. |
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Figure 10 Fully height-adjustable office desks
Figure 12 Adjustments on an office chair
Cabinets, shelves and other storage facilities
Ensure that cupboards, shelves, filing cabinets and room dividers (screens) are stable.
Where items are stored at a height of 1.80 m or greater, provide your employees with suitable climbing aids (e.g. steps, rolling step stool, ladder).
The following are generally stable:
Furniture with a high dead weight and low centre of gravity
Furniture secured to ceilings, walls or other furniture to prevent it from falling
Cupboards and filing cabinets with additional weights, additional anchoring or anti-tipping interlocks
Cupboards and shelves in compliance with the recommendations stated in Figure 13
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Figure 13 Ratio of the footprint depth to the height of the highest shelf
3.3.3 VDUs
One of the most important items of work equipment at an office workplace is the VDU. The quality of the screen and its settings determine to a considerable degree whether your employees are able to work free of health complaints. Incorrect height adjustment for example may lead to postural complaints, excessive screen brightness to eye problems.
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At a VDU workstation, unergonomic VDU design or unfavourable screen settings may present hazards for the eyes or the locomotor apparatus, particularly tension caused by constrained posture.
Possible hazards are:
Constrained or incorrect posture caused by excessively high VDUs, excessively small fonts or unfavourable arrangement of multiple screens
Stress upon the eyes caused by overly reflective VDUs, blurred or excessively small fonts or an imbalanced brightness ratio in the field of vision
Mental fatigue caused by a need for elevated attention and concentration
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Reduce these hazards by implementing the measures below.
Procure VDUs that can be lowered to just above the surface on which they stand. Ideally, your employees should view the screen by looking downwards at an angle of approximately 30° to 35° below the horizontal.
Ensure that the screen is angled backwards such that your employees view it perpendicular to the surface.
Give preference if possible to anti-reflective screens (matt screen display), in order to avoid disturbing reflections; these are detrimental to character contrast and make characters harder to recognize.
Figure 14 VDU arrangement
Figure 15 Disturbing reflections
VDUs are divided into three reflection classes according to their reflection properties.
The reflection classes commonly used in the past are no longer stated. Instead, the conditions are stated under which the reflections on the screen are measured (first column of the table below). The statement " LREF,EXT = 200 cd/m2 and LREF,SML = 2000 cd/m2" on the GS certificate corresponds to the former Reflection Class I. A screen with these properties can be used in all office environments. |
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Table 9: Assignment of VDUs to reflection classes
Components of illumination (cd/m2) | Suitable environment | Former reflection classes to EN ISO 13406-2 | |
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LREF,EXT = 200 and LREF,SML = 2000 | Suitable for general office use * | I | |
LREF,EXT = 200 or LREF,SML = 2000 | Suitable for most, but not all, office environments ** | II | |
LREF,EXT = 125 or LREF,SML = 200 | Requires a specially controlled luminous environment *** | III | |
REF,EXT = luminance of the large aperture source; REF,SML = luminance of the small aperture source | |||
* | VDUs of this type can be used in any office environment. | ||
** | On these VDUs, disturbing reflections on the screen must be anticipated under sub-ideal lighting conditions or when the equipment is situated close to a window. | ||
*** | On these VDUs, disturbing reflections are generally so strong that the screens cannot be considered for office work in normal office environments. These disturbances can be avoided only by the use of fully diffuse illumination, which for technical reasons is virtually unachievable, and at same time measures to prevent bright surfaces (walls, windows) from reflecting on the screen. |
Note that your employees will be less well able to distinguish colours on the screen with rising illuminance, particularly on anti-reflective screens.
Note from the manufacturer's information the illuminance for which the screen is suitable. In order for VDUs to deliver distinguishable colours even at workstations adjacent to windows, use screens with a designated screen illuminance illuminance of at least 1,500 to 2,000 lux.
Procure VDUs with light-coloured, matt casings, since these are more suitable for use in bright environments and for true video (i.e. dark characters on a light background), which is the display form most commonly used on VDUs. This results in a balanced brightness distribution in the user's field of view. Your employees' eyes are not exposed to unnecessary brightness adjustment (adaptation).
Operate LCD screens at the highest possible (physical) resolution, in order to attain the best character sharpness.
Do not fit monitor filters to VDUs, since these are generally detrimental to the display quality of the screens.
Should your employees work with several windows open or with scanned documents, the choice between one large VDU (e.g. 22, 24 or 27 inch) or two small screens depends upon the work task. On a 19 inch screen in portrait orientation, DIN A4 documents can be displayed well and can also be enlarged easily for documents with small fonts.
In order for your employees to avoid excessive head and eye movements and the health complaints potentially resulting from them when working with large or multiple screens, you should use narrow and small screen combinations if possible. This applies in particular to employees whose field of vision is narrowed by the use of varifocal glasses. Where a multi-screen solution is used, the screens should have narrow casing frames and be located close together. Use screens with a low viewing angle dependence (i.e. do not use TN (twisted nematic) mode display).
Employees may require special VDU glasses in order to improve their visual function when working at VDUs. (This is not generally necessary before the age of 40.) Have your employees consult your occupational physician, and do so yourself.
3.3.4 Input devices
Keyboards and mice are generally used as the input devices at office workplaces. Here too, pay attention to ergonomic design. Unergonomic design or unsuitable settings or placement may lead to disorders in the musculoskeletal system and/or the eyes.
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Hazards exist for your employees with regard to:
The locomotor apparatus
The eyes
Risk factors for the incidence of such disorders are:
Constrained or incorrect posture caused by excessively high keyboards and mice and by unfavourable location of these devices
Eye stress caused by an excessively high brightness ratio in the field of vision, glossy surfaces (particularly keyboard keys), and keyboard markings that are too small
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You can reduce the above hazards by means of the following measures:
Keyboard
Procure keyboards that are as shallow as possible. The height of the keyboard (i.e. of the middle row of keys) must not exceed 30 mm. This can be attained only with the keyboard feet folded down. When the keyboard meets this requirement, your employees do not need a rest for the heel of the hand.
Ensure that surface in front of the keyboard has a depth of 100 mm to 150 mm. This area is large enough for the hands to be rested upon it.
Where textual and numerical data are to be input or data edited, use full keyboards with alphanumeric, numeric, editing and function keys. When numeric input is required infrequently or the mouse is primarily used, select compact keyboards without a numeric key block. This results in a relaxed, neutral arm posture for your employees (Figure 17).
Figure 16 Arrangement of the keyboard on the work surface
Procure keyboards on which the key markings are easily legible.
To be easily legible, key markings should have an adequately large character height of at least 2.9 mm (preferably 3.2 mm) and dark characters on a light background with good contrast (see Figure 18).
Figure 17 Position of a full keyboard (top) and a compact keyboard with easier access to the mouse area (bottom)
Benefits of light-coloured keyboards Light keyboards with dark lettering are better suited to the use of true video on the VDU, i.e. dark characters on a light background. They avoid disturbing differences in brightness and thus save your employee's eyes unnecessary adaptation to these differences. The surfaces of keys become shiny after longer use, as a result of either wear or sweat from the fingers. This is less apparent on light keys than on dark keys. |
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Figure 18 Requirements concerning keyboards
Mouse
Procure mice that are suitable for the size of the user's hand and enable the heel of the hand to rest upon the work surface. Symmetrical mice can be used by either hand. Mice are also available specifically for left-handed or right-handed users (see Figure 19).
The mouse buttons should function reliably and be easy to use, and should provide feedback when operated. Your employees should be able to operate the mouse whilst adopting a normal body and hand posture, without their position changing inadvertently as a result.
Ensure that the mouse has an adequate area of movement adjacent to the keyboard. A thin mouse pad is useful in this respect.
Figure 19 Sizes of mouse
Alternative input devices
For employees with chronic diseases or constraints upon their movement, special, alternative input devices (such as a vertical mouse or split keyboard) may have to be procured. Consult your occupational physician in this case.
3.3.5 Software ergonomics
Software influences performance and productivity in office work. Software with high usability also influences the quality of the work results. Software of good ergonomic design has a positive influence upon physical and mental stress and the satisfaction and motivation of your employees.
Figure 20 The software design influences performance of the tasks
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Software of unergonomic design may give rise to physical and mental hazards:
Elevated stress upon the eyes and vision
Mental fatigue caused by high stress upon memory, high demands upon attention and concentration
Monotony caused by repetitive work steps or tasks
Mental satiation, caused for example by illogical and contradictory operation of the software
Stress, caused for example by poor orientation where software is badly structured or fails to work correctly
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General measures
Ensure that the software is fit for purpose, i.e. that the users are able to use it to perform their tasks effectively, efficiently and satisfactorily. The employees must be capable of completing tasks for which software is used.
Ensure that the software can be adapted to different VDUs, other hardware (e.g. different input and output devices) and different ambient conditions.
Involve your employees in the selection and procurement of software.
Measures for interaction design
Ensure that interaction with the software is appropriate for the task: all tools and information required for completion of the task must be provided in full by the software; unnecessary functions and information should be avoided.
Figure 21 Application unsuitable for the task owing to the overload of tools
Ensure that the software used is self-descriptive: software dialogs should be of comprehensible design and should provide appropriate explanations either by immediate feedback or on demand.
Ensure that the software satisfies the expectations of users. It should be suitable for the context of use, the users' personal abilities and skills, the task in hand, and generally established conventions.
Give preference to software that promotes learning, guides users during familiarization with its operation, supports them in its use, and promotes the generation of knowledge.
Ensure that operation of the software is user-driven: it should be possible to launch the dialog process and to influence its course and pace through to completion of the work task with no loss of data.
Ensure that the software used is tolerant of faults: should inputs be made that are evidently incorrect, the intended result of the work should be attainable with reasonable correction effort, if any. Constructive explanations should be provided in the event of errors.
Ensure that the software used by your employees can be customized to their individual needs and skills by adjustment of the presentation of information and operation of the software.
Figure 22 Example of negative and positive fault tolerance
Measures for information design
Ensure that the software provides the employees with information in an accessible, comprehensible and legible form.
Ensure that text, symbols and other elements contrast well with the background. Contrast levels and the suitability of colour combinations can be determined for example by means of the contrast analyser (see Figure 23). A theoretically determined contrast for normal fonts should be at least 4.5:1; a contrast greater than 7:1 is recommended.
Note: The contrast analyser and the measurement slide template for you to print out yourself can be found at: www.vbg.de/softwareergonomie. Note that the contrast analyser determines the contrast from the programmed values; the actual contrast on the VDU may differ. |
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Figure 23 Information on the contrast analyser
In order to improve the legibility and identifiability of characters and symbols, avoid unfavourable colour combinations.
Figure 24 Unfavourable colour combinations
Colour coding can be useful for orientation. Information should be coded in an additional form, for example by a symbol, pattern or character (e.g ).
Use sans-serif fonts such as Verdana, Arial, Calibri and Tahoma for reading on the screen.
Figure 25 Fonts
Use a minimum character height to ensure reliable legibility.
Table 10 Character height for capital letters
Viewing distances | |
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Viewing distance | Recommended character height in mm |
500 | 3.2 to 4.5 |
600 | 3.9 to 5.5 |
700 | 4.5 to 6.4 |
800 | 5.2 to 7.3 |
Observe the organizational principles governing the arrangement of elements and information (for example by proximity, type, symmetry), in order to facilitate the perception, location and categorization of information (see Figure 26).
Pay attention to the design of forms and their logical subdivision.
Figure 26 Example of application of the organizational principles
3.3.6 Health in offices
Long periods spent sitting, physical inactivity and particular demands upon eyesight may impair the health of your employees at office workplaces. Musculoskeletal and eye disorders are not uncommon. Mental impairments may also arise.
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Hazards |
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Your employees face hazards in particular as a result of:
Poor workplace ergonomics
Lack of movement
Continual stress upon the eyes and vision
Deficits in work organization, such as inappropriate management behaviour, overload and underload, frequent interruptions, time pressure
Diseases of the musculoskeletal system top the list of reasons for absences from work.
Office workers also frequently complain of musculoskeletal disorders, particularly
tension in the cervical spine with impact upon the shoulder-arm system, and in the
lumbar spine. A lack of movement also increases the risk of obesity, cardiovascular
disorders and diabetes. An eye defect that is not (adequately) corrected can give
rise to eye fatigue. Mental impairments influence employees' well being, and can contribute to the incidence of diseases. |
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Measures |
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The measures below assist you in designing your employees' workplaces to be conducive to their good health, which in turn supports their employability:
Promote dynamic sitting (i.e. alternation between a forward, middle or rearward sitting posture) by procuring suitable office chairs.
Avoid your employees being exposed to imbalanced physical work stresses by ensuring that the necessary free movement areas are not obstructed and that work processes involve alternating tasks.
Locate printers, photocopiers and fax machines at a central point and not directly at the workstations.
Provide your employees with standing-height or adjustable-height desks.
Promote movement by conducting discussions with employees away from their workstations and occasionally also standing.
Motivate your employees to exercise more, for example by: climbing stairs rather than taking the lift; using the walk to the printer, photocopier or fax machine as a form of exercise; exercising regularly at their workstations.
Alternation between sitting and standing is good; alternation between sitting, standing and walking is even better. This promotes movement of the spine, contributes to the intervertebral disks being supplied with oxygen and nutrients, releases tension, stimulates the cardiovascular system, and enhances concentration. Support your employees in this alternation.
Check whether you are able to offer means of promoting regular exercise, for example as part of your workplace health management policy. Lifestyle changes are much easier to achieve in a group of like-minded colleagues.
Ensure that arrangements for work organization and task completion are healthy, for example by avoiding overload and underload, ensuring a good workplace atmosphere and adopting a health-conscious management style (see Chapter 3.1).
Exercise or massage
Your company should preferably offer training measures to promote exercise, in order to reduce health complaints among your employees and to reduce the stresses to which they are exposed. Health deficits attributable to a lack of movement can thereby be avoided. Conversely, massages do not address the conditions that give rise to muscle tension, but merely alleviate the symptoms temporarily.
Provision of preventive occupational medical care by the occupational physician
As an employer, you are required to offer employees who work at VDU workstations preventive occupational medical care appropriate to these tasks at regular intervals. The preventive occupational medical care may reveal a requirement for you to provide special optical aids (VDU workstation glasses) to the employees concerned.
When determining the number, also consider persons who may access the workstation for brief discussions or meetings.