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1、BRITISH STANDARD BS 7179-6: 1990 Ergonomics of design and use of visual display terminals (VDTs) in offices Part 6: Code of practice for the design of VDT work environments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:40:38 GMT+00:00 2006, Uncontrolled Cop
2、y, (c) BSI BS 7179-6:1990 This British Standard, having been prepared under the direction of the Personal Safety Equipment Standards Policy Committee, was published under Amendments issued since publication the authority of the Board of BSI and comes into effect on 30 November 1990 BSI 12-1998 The f
3、ollowing BSI references relate to the work on this standard: Committee reference PSM/39 Draft for comment 87/40679 DC ISBN 0 580 18004 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Personal Safety Equipment Standards Policy Committee
4、 (PSM/-) to Technical Committee PSM/39, upon which the following bodies were represented: AERC Institute of Engineering Research British Airways British Industrial Truck Association British Occupational Hygiene Society British Telecommunications plc Business Equipment and Information Technology Asso
5、ciation Chartered Institution of Building Services Engineers Engineering Employers Federation Ergonomics Society Health and Safety Executive ICE (Ergonomics) Ltd. Institute of Management Services Institute of Occupational Medicine Loughborough University of Technology Ministry of Defence National Un
6、ion of Mineworkers Society of Motor Manufacturers and Traders Limited Society of Occupational Medicine Trades Union Congress Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:40:38 GMT+00:00 2006, Uncontr
7、olled Copy, (c) BSI BS 7179-6:1990 BSI 12-1998i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3General guiding principles2 4Work environment2 Appendix A Bibliography4 Publication(s) referred toInside back cover Licensed Copy: London South Bank University, Lo
8、ndon South Bank University, Fri Dec 08 10:40:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7179-6:1990 ii BSI 12-1998 Foreword This Part of BS 7179 has been prepared under the direction of the Personal Safety Equipment Standards Policy Committee. This Part of BS 7179 deals with the work environme
9、nt for VDT users. The objective is to provide a work environment which will facilitate the efficient operation of the visual display terminal (VDT) and provide the user with comfortable working conditions. In particular, the combined effects of light, noise and heat are important in determining the
10、work environment. Other Parts of this standard are: Part 1: Introduction; Part 2: Recommendations for the design of office VDT tasks; Part 3: Specification for visual displays; Part 4: Specification for keyboards; Part 5: Specifications for VDT workstations. Details of further sources of information
11、 on the workplace environment are given in appendix A. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal
12、 obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment tabl
13、e on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:40:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7179-6:1990 BSI 12-19981 1 Scope This Part of BS 7179 provides guidance on the preferred characteristics of the quality and quanti
14、ty of light, noise and heat in offices used for visual display terminal (VDT) work. Requirements for visual displays, keyboards and workstations are covered in other Parts of this standard. NOTEThe titles of the publications referred to are listed on the inside back cover. 2 Definitions For the purp
15、oses of this Part of BS 7179, the definitions in BS 7179-1 apply together with the following. 2.1 illuminance the amount of light falling on a given surface. It is measured in lux NOTEA more complete definition is given in BS 5775-6. 2.2 luminance at a point of a surface and in a given direction, th
16、e luminous intensity of an element of the surface, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction 2.3 visual field the full extent of what can be seen when looking in a given direction 2.4 contrast used subjectively, it describes the
17、difference in appearance of two parts of a visual field seen simultaneously or successively. The difference may be one of brightness, colour or both. Used objectively, the term expresses the luminance difference ratio in a numerical form NOTESee also 2.12 of BS 7179-3:1990. 2.5 glare condition of vi
18、sion in which there is discomfort or a reduction in the ability to see significant objects or both due to an unsuitable distribution or range of luminance or to extreme contrasts in space or time 2.6 disability glare (dazzle) glare which impairs the ability to see detail without necessarily causing
19、visual discomfort 2.7 discomfort glare glare which causes discomfort without necessarily impairing the ability to see detail 2.8 direct glare glare caused when excessively bright parts of the visual field are seen directly, e.g. lamps which are inadequately shielded 2.9 reflected glare a term used t
20、o describe various visual effects, such as the reduction of contrast, discomfort or distraction, produced by the reflection of light sources or other bright areas in non-matt surfaces 2.10 CIE glare index a numerical index which enables the discomfort glare from lighting installations to be ranked i
21、n order of severity and the permissible limit of discomfort glare from an installation to be prescribed quantitatively 2.11 reflectance the ratio of light reflected from a surface to the light incident upon it 2.12 local lighting lighting designed to illuminate a particular small area which usually
22、does not extend far outside the visual task 2.13 cathode ray tube (CRT) a device commonly used as a computer terminal/word processor display. It consists of a vacuum tube in which an electron beam is deflected onto a fluorescent screen producing visible spots of light 2.14 liquid crystal display (LC
23、D) a display device which works on the principle that a liquid crystal polarizes light when a voltage is applied to it 2.15 decibel dB(A) the unit of measurement of sound intensity. It is on a logarithmic scale therefore an increase of 3 dB represents a doubling of the intensity of the sound. The (A
24、) scale is weighted to take account of the frequencies which most affect the human ear NOTEA more complete definition is given in BS 5775-7. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:40:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7179-6:1990 2 BSI
25、12-1998 3 General guiding principles Even when it is possible to control the work environment within strict limits, individuals working in that environment will vary in their judgements of its acceptability. This is partly because of the range of personal preferences and partly because different tas
26、ks may require quite different environments. For example, users who sit at VDTs for prolonged periods are far more sensitive to draughts than users whose work involves moving about the room only working at the VDT intermittently. Similar differences between individuals apply to the visual and acoust
27、ic environment also. In fact VDT work often restricts the opportunities that individuals have for moving about in a room and so some degree of individual control over the environment is highly desirable. In large rooms containing many people, care should be taken to ensure that one persons preferred
28、 conditions do not interfere with the comfort of other people in the room. For example, a desk lamp may be positioned to illuminate documents on a desk top, but it may also be the cause of glare to someone working elsewhere in the room. 4 Work environment 4.1 Lighting 4.1.1 General level of illumina
29、nce The general level of illuminance should be between 300 lx and 500 lx measured horizontally at work surface height. NOTEHigh illuminance will make the characters on CRT type displays less easy to see but will improve the ease of reading source documents. Thus if a display can be viewed comfortabl
30、y with a higher ambient illuminance there is no need to restrict levels to those suggested. 4.1.2 Local lighting Additional local lighting may be required, depending on the task and the type of display used. CRT type displays are less likely to suffer reduced contrast between the image and its backg
31、round if the general illuminance does not exceed 500 lx, but at this level, local lighting may be needed to enable comfortable reading of source documents. Passive displays, e.g. LCDs, may also require additional lighting to be easily read. It is essential that any local lighting is under the contro
32、l of the person for whom it is provided. 4.1.3 Glare 4.1.3.1 Sharp contrasts between different areas in the field of view should be avoided. Glare from bright areas which are not the focus of attention can cause discomfort, and, in extreme cases, prevent people from being able to do the task in hand
33、. For example, bright reflections on the screen can mean that information displayed cannot be read. An example of discomfort glare is where a VDT users attention is distracted away from the screen because a bright area elsewhere in the room attracts the eye. 4.1.3.2 Glare can be minimized, if not co
34、mpletely avoided, by using the following techniques. a) Light fittings should be shielded so that the source of light is not visible from working positions. The use of shades or shields around the fittings and indirect lighting such as uplighters should be explored. b) The amount and direction of da
35、ylight through windows should be controlled. Internal blinds and curtains, external shades and reduced transmission glass are all techniques which can be applied. c) The room should be arranged bearing in mind the effects of natural and artificial lighting on the equipment to be used and the tasks t
36、o be done. NOTE 1For example CRT displays used in bright conditions will have reduced contrast between the displayed image and its background whereas liquid crystal displays need a light source because they operate by reflecting light. d) The equipment should be arranged on the workstation to make t
37、he best use of local light conditions and to avoid any potential problems. The display screen should ideally be placed at right angles to windows and between (and parallel to) rows of luminaires. Source documents should be placed in well lit areas of the workstation. e) The tilt and swivel adjustmen
38、ts on the display (or workstation) and other equipment (such as copy holders) should be used to get optimum working conditions. f) Anti-glare “treatment” of the display surfaces is now common and may prevent any adverse effects of working with displays in offices with inappropriate lighting. NOTE 2E
39、xamples of such are, louvres, meshes, polarizers, hoods, sprays, filters. These reduce luminance but improve contrast, but resolution may be poorer. When such are used it is essential to ensure that the display complies with Part 3 of BS 7179. The effectiveness of anti-glare treatments may vary with
40、 different lighting conditions. t reatments t reatments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:40:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7179-6:1990 BSI 12-19983 g) For rooms where VDTs are used, a CIE glare index of 16 is recommended (see
41、“Lighting for spaces where visual display terminals are used”). 4.1.4 Surface reflectance Surfaces which have a high reflectance may cause glare. The reflectance of all surfaces in the field of view should therefore be carefully considered. A general rule for surface reflectance is that it should de
42、crease from ceiling (usually about 75 %) to floor (20 % to 40 %). 4.2 Noise 4.2.1 Noise level The noise level in a VDT workplace should not exceed 55 dB(A) for tasks requiring a high degree of concentration, and 60 dB(A) for other VDT tasks. 4.2.2 Techniques for minimizing effects of noise 4.2.2.1 N
43、oisy items of equipment, such as printers, should stand on a surface which absorbs the sound. If the noise generated is still high then an acoustic cover or acoustic screen should be fitted. 4.2.2.2 Noisy equipment should be located away from people whose concentration might be disturbed. However, t
44、he location should still be convenient for those who need access to the equipment. 4.3 Thermal conditions 4.3.1 General The introduction of electronic equipment into an office is likely to alter the thermal environment. For example, the equipment can generate heat and create air movement. It is poss
45、ible to recommend optimum ranges for each of the factors which affect performance and comfort, namely, temperature, air movements (draughts) and humidity, but it should be remembered that, in practice, it is the combined effect of all factors and the personal preference of the occupants of a room wh
46、ich determine whether they judge it to be satisfactory or not. 4.3.2 Ambient temperature The ambient room temperature should be between 19 C and 23 C. For jobs which involve extensive periods of seated work, the difference between the temperature at floor level and that at head level should not exce
47、ed 5 C. The heat build up in areas around equipment should not exceed 3 C above the ambient level. External surfaces which can be touched should have a surface temperature no higher than 50 C. 4.3.3 Air movements The rate of air movement should be less than 0.25 m/s but it is recommended that the ai
48、r should be changed at a rate of 1.3 L/s/m2. Where any components of equipment use a cooling fan, the air expelled by the fan should not cause discomfort to the equipment operator or to nearby operators. 4.3.4 Relative humidity The relative humidity should be between 40 % and 60 %. For advice on the
49、 control of undesirable static electricity reference should be made to BS 5958. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:40:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7179-6:1990 4 BSI 12-1998 Appendix A Bibliography The following documents are listed for information. Chartered Institute of Building Services Engineers. Code for interior lighting. CIBSE 19841). Health and Safety Executive. Visual display units. HMSO 19832). International Organization for Standardization. Thermal environments Inst