Lighting for health and safety

232 Pages·2000·9.819 MB·xii, 227 p. : ill\232

by  N A Smith

Contents
Preface xiii
Acknowledgements xiv
1 Introduction 1
1.1 History of light sources 1
2 Fundamentals
2.1 The electromagnetic spectrum
2.2 Optical radiation
2.3 Ultraviolet and infrared radiation
2.4 Continuous and discontinuous radiation
2.4.1 Spectral power distribution (SPD)
2.5 Black body radiation
2.6 Wavelength, frequency and the velocity of
propagation of light 8
2.7 Radiant flux and radiant efficiency 8
2.8 Luminous flux, luminous efficacy and luminous
efficiency 8
2.9 Luminous intensity 8
2.10 Illuminance and luminance 9
2.11 Luminosity 10
3 Laws of illumination 11
3.1 Inverse square law 11
3.2 Cosine law 12
3.3 Combination law 14
3.4 Relationship between luminous intensity and
luminous flux 15
3.5 Relationship between illuminance and luminance 16
3.6 Specular reflection 17
3.7 Refraction 18
3.8 Dispersion 18
vi Contents
3.9 Absorption and scattering 19
3.10 Diffuse reflection and diffuse transmission 20
4 Physiology and characteristics of vision 21
4.1 Introduction 21
4.2 Structure of the human eye 21
4.3 Photoreceptors - rods and cones 23
4.4 Neurophysiology 25
4.5 Formation of images on the retina 25
4.6 Blind spot 27
4.7 Excitation of rods 27
4.8 Excitation of cones 28
4.9 Visual pathway 29
4.10 Spectral sensitivity of the eye 30
4.11 Radiation and the eye 32
4.12 Visual threshold 32
4.13 Photopic and scotopic vision 33
4.14 Mesopic vision 34
4.15 Visual discrimination 35
4.16 Accommodation, convergence and stereopsis 35
4.17 Field of vision 38
4.18 Adaptation 38
4.18.1 Dark adaptation 38
4.18.2 Light adaptation 40
4.18.3 Problems associated with twilight 40
4.18.4 Colour adaptation 41
4.19 Visual acuity 41
4.19.1 Photopic acuity 43
4.19.2 Relationship between cones and visual acuity 43
4.19.3 Scotopic acuity 44
4.19.4 Static and dynamic visual acuity 45
4.20 Visual perception 45
4.20.1 Perception by sight 46
5 Defects and anomalies of vision 47
5.1 Introduction 47
5.2 Glare 47
5.2.1 Induction and disability glare 47
5.2.2 Phototropism and discomfort glare 48
5.3 Persistence of vision 49
5.4 After-images 49
5.5 Flicker 49
5.6 Hypermetropia 50
5.7 Myopia 50
5.8 Presbyopia 51
5.9 Astigmatism 52
5.10 Diplopia 52
5.11 Colour blindness 53
5.11.1 Monochromats 53
5.11.2 Dichromats 53
Contents vii
5.11.3 Trichromats 53
5.12 Colour vision tests 53
5.13 Night blindness 54
5.14 Effects of age 55
5.15 Glaucoma 55
6 Colour 56
6.1 Colour definitions and terminology 56
6.1.1 Hue, lightness and saturation 56
6.1.2 Munsell colour solid 56
6.2 CIE chromaticity diagram 57
6.3 Planckian radiator 57
6.4 Dominant wavelength 59
6.5 Chromaticity of the visible spectrum 60
6.6 Lamp colour appearance 61
6.7 Colour temperature and correlated colour temperature 61
6.8 Colour rendering and colour rendering index (CRI) 63
6.9 Colour contrast 65
6.10 Colour perception and production 66
6.11 Colour mixing and complementary colours 67
6.12 Colour coding 68
6.12.1 Colours used for transport signals 70
6.13 Metamerism 70
6.14 Photochromism 71
6.15 Achromatic interval 71
6.16 Effects of environmental colour on individuals 72
7 Natural and artificial light sources 73
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7.1 Daylight 73
7.2 Availability of daylight 73
7.3 Daylight factor 74
7.4 Emission of light from heated bodies 75
7.5 Types of spectra 76
7.6 Emission of light from gas discharges 77
7.7 Tungsten lamps 78
7.7.1 Tungsten filament lamps 78
7.7.2 Tungsten halogen lamps 79
7.7.3 Dichroic reflector lamps 81
7.8 Discharge lamps 82
7.8.1 Introduction 82
7.8.2 Low pressure mercury or fluorescent lamps 84
7.8.3 High pressure mercury vapour lamps 86
7.8.4 Metal halide lamps 87
7.8.5 Low pressure sodium lamps 88
7.8.6 High pressure sodium lamps 91
7.8.7 Induction lamps 92
7.9 Lasers 93
7.9.1 Display laser lighting installations 94
7.10 Optical fibres 95
7.11 Luminescence 95
viii Contents
7.12 Lamp characteristics 96
7.12.1 Lamp designations 96
7.12.2 Lamp efficacy 96
7.12.3 Lamp life 98
7.12.4 Lamp applications 98
7.12.5 Lamp run-up efficiency 98
7.13 Blue light hazard 100
7.14 Lamps used for other than normal lighting
applications 100
7.15 Standard illuminants 102
7.16 Beta lamps 103
7.17 Tyndall beam lamp 104
7.18 Handling of new lamps and the disposal of spent
lamps 105
7.19 Ultraviolet radiation from tungsten halogen lamps 106
7.20 Ultraviolet radiation from high intensity discharge
lamps 107
7.21 Effects of operating broken mercury vapour and
metal halide lamps 107
8 Luminaires 109
8.1 Introduction 109
8.2 Optical control of light output from luminaires 110
8.3 Distribution of light from luminaires 112
8.3.1 Polar diagram 113
8.3.2 Isocandela diagram 113
8.3.3 Isolux diagram 113
8.4 Luminaires for hazardous and hostile environments 113
8.5 Classification of luminaires according to relevant
British Standards 115
8.5.1 BS 4533 115
8.5.2 BS 5345 115
8.5.3 BS 6467 116
8.6 Downlighter luminaires 116
8.7 Air handling luminaires 117
8.8 Uplighter luminaires 117
8.9 Luminaire materials 118
8.10 Mechanical strength of luminaires 119
8.11 Control gear 119
8.12 Electromagnetic interference (EMU and radio
frequency interference (RFI) 120
8.13 Polychlorinated biphenyls (PCBs) 120
9 Lighting for interior applications 121
9.1 Introduction 121
9.2 Office lighting 121
9.3 Techniques and practice of interior lighting 122
9.4 Lumen method of lighting design 123
9.5 Preferred illuminance and luminance ratios
for interiors 124
Contents ix
9.6 Lighting for areas containing display screen
equipment 125
9.7 Uplighter installations 125
9.8 Lamp types for use in interiors 128
9.9 Methods of reducing glare from windows 129
9.9.1 Temporary methods 129
9.9.2 Permanent methods 129
9.10 Room index 130
9.11 Automatic control of lighting within offices 130
9.12 Emergency lighting 132
9.12.1 Emergency escape lighting 132
9.12.2 Stand-by lighting 132
9.12.3 Escape route lighting 132
9.12.4 Open area (anti-panic area) lighting 133
9.12.5 High risk area task lighting 133
9.12.6 Luminaires for use in emergency lighting
installations 133
9.13 Sick building syndrome and building related illness 133
10 Lighting for external applications 135
10.1 Introduction 135
10.2 Factories 135
10.2.1 General factory external layout lighting 135
10.2.2 Lighting for loading bays 136
10.2.3 Lighting for storage areas 136
10.3 Security lighting 137
10.3.1 Security lighting for shops and small premises 138
10.3.2 Security lighting for offices 138
10.3.3 Security lighting for factories 139
10.4 Floodlighting 140
10.4.1 Building floodlighting 140
10.4.2 Industrial floodlighting 141
10.4.3 Sports floodlighting 143
10.5 Public lighting 143
10.5.1 Road lighting 144
10.5.2 Tunnel lighting 145
10.6 Lighting for externally located advertising signs 146
10.7 Lighting for use with closed circuit television
(CCTV) systems 146
10.8 Light pollution 148
10.8.1 Causes 148
10.8.2 Remedies 149
11 Visual task lighting 150
11.1 Introduction 150
11.2 Importance of lighting in the workplace 150
11.3 Analysis of the working visual task 151
11.4 Visibility of an object 153
11.5 Factors influencing the ability to see detail 153
11.6 Quality of illumination 154
x Contents
11.7 Visual comfort 154
11.8 Glare in the working environment 156
11.8.1 Control of discomfort glare 156
11.8.2 Direct and reflected glare 157
11.9 Veiling reflections 159
11.10 Use of daylight for task lighting 161
11.11 Luminance contrast and contrast rendering
factor (CRF) 162
11.12 Uniformity ratio and diversity ratio 164
11.13 Spacing-to-height ratio (SHR) 164
11.14 Influence of illuminance on human visual
characteristics 165
11.15 Flicker and the stroboscopic effect 165
11.16 Light modulation 166
11.17 Loss of perception 168
11.18 Poor task lighting - effects on worker posture 168
11.19 Effects of age of individual on task vision 169
11.20 Preferred task lighting strategies 171
11.21 Typical recommended illuminance values 173
12 Lighting for specific industries and occupations 175
12.1 Introduction 175
12.2 Lighting for inspection 175
12.2.1 General inspection lighting techniques 175
12.2.2 Detection of form defects 175
12.2.3 Detection of detail defects 177
12.2.4 Detection of colour defects 177
12.2.5 Special techniques for inspection lighting 177
12.3 Lighting for engineering workshops 178
12.4 Lighting for textile and clothing manufacturing
industries 179
12.5 Lighting for building and construction sites 179
12.6 Lighting for electrical and electronic equipment
manufacture and assembly 181
12.7 Lighting for food and drink industries 181
12.8 Lighting for metal working industries 182
12.9 Lighting for furniture and timber industries 182
12.10 Lighting for glass industries 182
12.11 Lighting for premises used for health care 182
12.12 Lighting for paper and printing industries 183
12.13 Lighting for mining 183
12.14 Lighting for hazardous and hostile environments 184
12.15 Lighting for dockyards and shipbuilding 184
12.16 Lighting for horticulture 185
12.17 Workers exposed to ultraviolet radiation 185
13 Lighting and display screen equipment 187
13.1 Introduction 187
13.2 Radiation associated with the use of display
screen equipment 187
Contents xi
13.3 Screen image 188
13.3.1 Resolution 190
13.3.2 Flicker and refresh rate 190
13.3.3 Jitter 191
13.3.4 Screen contrast 191
13.3.5 Active and passive displays 191
13.3.6 Cathode ray tubes (CRTs) 191
13.3.7 Liquid crystal displays (LCDs) 191
13.4 Glare control on VDU screens 191
13.5 Lighting for VDU areas 192
13.6 Optimum conditions for visual comfort in display
screen equipment operators 194
14 Lighting surveys 197
14.1 Introduction 197
14.2 Instrumentation 197
14.2.1 Illuminance measuring equipment 198
14.2.2 Luminance measuring equipment 198
14.2.3 Daylight factor meters 198
14.3 Survey methods 198
14.3.1 Determination of the minimum number of
measuring points 199
14.3.2 Presentation of information 199
14.3.3 Method of separating illuminance contributions
due to daylight and artificial lighting 202
14.4 Interpretation of the data obtained 203
14.5 Recommendations 204
15 Legislation 206
15.1 Overview 206
Appendix A: Legislation in the United Kingdom 207
A.l Introduction 207
A.2 Acts, regulations and approved codes of practice 208
A.3 The law relating to lighting 208
A.3.1 Management of Health and Safety at Work
Regulations 1992 208
A.3.2 Wgrkplace (Health, Safety and Welfare)
Regulations 1992 209
A.3.3 Health and Safety (Display Screen Equipment)
Regulations 1992 210
A.3.4 Health and Safety (Safety Signs and Signals)
Regulations 1996 210
A.3.5 Provision and Use of Work Equipment
Regulations 1998 210
A.3.6 Electricity at Work Regulations 1989 211
A.3.7 Electromagnetic Compatibility Regulations
1992 211
A.3.8 Docks Regulations 1988 212
xii Contents
A.3.9 Electrical Equipment (Safety)
Regulations 1994 212
A.3.10 Supply of Machinery (Safety)
Regulations 1992 212
A.3.11 Control of Substances Hazardous to Health
Regulations 1994 212
A.3.12 Special Waste Regulations 1996 (as amended) 213
A.4 Compliance with health and safety law 213
References 215
Suggested further reading 217
Index 219
Chapter I2
Lighting for specific industries
and occupations
12. I Introduction
It is not possible to include lighting applications which are applicable to
all industries and occupations, but a selection is included which is
considered to be representative.
12.2 Lighting for inspection
The inspection of products in a production process is a necessary
element in monitoring the final quality of the finished article. The inspec-
tion may occur at various stages during the manufacture of a compo-
nent, but will invariably include an inspection of the final article. The
purpose of inspection, including visual inspection, is to identify any
individual feature of the component which, if left undetected, would
render it unsuitable for the purpose for which it is intended.
It will be evident that suitable and sufficient lighting contributes
significantly to the overall process of visual inspection.
12.2. I General inspection lighting techniques
The role of lighting for inspection is to improve the visibility of any
features of a product which would subsequently lead to its rejection as
a serviceable item. There is a multitude of manufactured products and
each one of them will have a different combination of features which
may prove defective in some way. It follows therefore that the optimum
inspection lighting required will vary from product to product. It will
be necessary to perform a visual task analysis in an attempt to achieve
optimum task lighting conditions. Those factors which are to be consid-
ered in such an analysis include:
176 Lighting for Health and Safety
The characteristics of the whole product which contains individual
features which are required to be inspected, i.e. general shape of the
product (two or three-dimensional), constitution of the product, e.g.
transparent, translucent or opaque and surface finish qualities of the
product, e.g. matt or specular.
The individual features within the whole product which require
inspection include form, detail and colour. Features of form are not
generally restricted to small size features and often tend to be seen as
part of the whole product, an example being inconsistencies in the
bodywork finish of a motor vehicle which become more apparent
when the whole vehicle body is viewed. Conversely features of detail
are small and can normally be detected when only part of the product
is being inspected, an example being a crack in the surface of some
solid material. It will be evident that the size of a product will not
usually influence colour features which require inspection.
Each individual inspection process has to be considered on its own
merits and it follows that each process will require careful consideration
in respect of the most appropriate lighting. However, as a general guide,
features of form are usually best illuminated by luminaires with strong
and clearly defined directional qualities of light output. Inspection of
features of detail are normally revealed more easily when the illumi-
nance levels are increased. The inspection of the surface colour features
of a product is a process which is heavily dependent upon the spectral
characteristics of the light sources used. Section 6.8 shows how the
spectral power distribution of light reflected from the surface of an object
is influenced by the combination of the spectral power distribution of
the light source used and the spectral reflectance characteristics of the
object being illuminated.
12.2.2 Detection of form defects
In general the form which a product appears to exhibit is strongly influ-
enced by:
the structural arrangement of the product;
the manner in which it is lit; and
the reflection characteristics of the material from which the product is
constructed.
In combination these will lead to the development of three characteris-
tic patterns:
illuminance;
highlight; and
shadow.
The complexity of products and of manufacturing processes necessitate
that lighting for discrimination of form be considered on its individual