Lighting and Colour PDF

CHAPTER – 9 Lighting and Colour THEME 1. Sight and light 5.1.1 Day, natural or General Lighting 2. Purpose & "Benefits of Good Lighting 5.1.2...

CHAPTER – 9 Lighting and Colour THEME 1. Sight and light 5.1.1 Day, natural or General Lighting 2. Purpose & "Benefits of Good Lighting 5.1.2 Artificial Lighting 2.1 Purpose and Advantages of Good lighting 5.1.3 Direct & Indirect Lighting 2.2 Effects of Bad Lighting 5.2 Types of Light Sources 2.3 Increase of Safety and Productivity 5.3 Types of Lighting Fittings due to Good Lighting. 5.4 Types of Lighting Installations 3. Principles of Illumination : 5.5 Cost of Lighting 3.1 Definitions 6. Design of Lighting Installation : 3.2 General Principles of Good lighting. 6.1 General Considerations 3.2.1 Adequate Illumination 6.2 Day lighting of Factory buildings 3.2.2 Glare 6.3 Installation for Artificial Lighting 3.2.3 Shadow 6.4 Plant Lighting Design 3.2.4 Uniform Lighting 7. Effects of Colour on Safety 3.2.5 Contrast 7.1 Need of Colours 3.2.6 Colour Contrast 7.2 Reflection Factors (LRV) 3.2.7 Colour Effect 7.3 Colour Code and Safety : 3.2.8 Flicker and Stroboscopic Effect 7.3.1 Indian Standards 4. Recommended Standards of Illuminations : 7.3.2 Colours to Identify Hazards 4.1 Statutory Provisions 7.3.3 Accident Prevention Signs 4.2 Indian Standards 7.3.4 Painting of Plant and Machinery 4.3 ILO Recommendation 7.4 Psychological Effects of Colour 5. Types of Light, sources, Fittings and 8. Maintenance of Lighting and Colour Installations : 5.1 Types of Light : 1 SIGHT AND LIGHT Sight and Light are the supreme need of life. Without eyes, sight and vision, life is incomplete. In Part 8.2.4 of Chapter 6, a Sanskrut stanza is given explaining that a mirror is of no use to him who has no eyes. The first and foremost sense required and being utilised for human activity is sight. The divine and powerful source of sight, light and life is the SUN whom we call 'Surya' and worship. It is the Sun only who is giving life to all of us and the whole universe, who throws ample light everywhere (if not obstructed) and gives sight to our eyes. Our artificial lighting is not at all comparable with its natural lighting, in terms of quantity, quality and cost. The fulfilment of almost all tasks depends on proper visual perception and it is estimated that about 80% of the sensory information for any work performance is received by brain through eyes only. Ordinarily all persons put reliance on sight than on any other senses, because without sight it is difficult to understand and judge about any object or action. Thus the importance of eyes, sight, or vision must first be understood. The human eye has visual acuity or an ability of accommodation i.e. the ability of the eye Fundamentals of Industrial Safety and Health 9- 1 Lighting and Colour  to change its effective focal length to see or distinguish objects distinctly at. varying distances. Adaptation ability of an eye is its sensitivity adjustment effected after sufficient exposure to light (light- adapted) or darkness (dark-adapted). Dazzling conditions and frequent adaptation may cause visual fatigue and eye troubles conductive to accidents. Convergence means an ability to get the impression of a single object through two images on the retinas of both eyes. Depth Perception or Stereopsis is the impression of depth gained from the fact that both eyes see an object from a slightly different angle. Sudden closure of eye-lids against excessive light is the safety response. Colour vision is due to the ability of the retina to distinguish between light of different wavelengths. It is not equally sensitive to all wave lengths. But the sight cannot do anything without light. The eye can portray to the brain only such impressions as are carried to it by light waves, and if these light waves are insufficient because of poor illumination, the effect is the defect in performance. Inadequate visual perception is a direct or indirect cause of many accidents. Visual perception depends on many factors which must be studied, to improve them. Some such factors are: 1. The eyesight of a person. 2. The quantity and quality of light on the object to be seen. 3. The size, shape, speed arid distance of the object. 4. The degree of colour contrast between the object and its background. 5. The obstructions, transparent or nontransparent, in the path of the light rays between the eye and the object. 6. Glare and shadow if any. Thus light, colour, their quantity and quality are the important factors for any visual perception and work performance-depends on it. 2 PURPOSE AND BENEFITS OF GOOD LIGHTING 2.1 Purpose and Advantages of Good lighting: Purpose, need, advantages or benefits of good lighting are many. There are three groups of working conditions : (1) Physical or environmental i.e. lighting, ventilation, noise, atmospheric conditions etc. (2) Relating to time i.e. hours-of work, rest pauses etc. and (3) Relating to social situation within which an individual works. The lighting influences all the three categories and is an important Fundamentals of Industrial Safety and Health 9- 2 Lighting and Colour working condition not only in factories but at all work places. Therefore it should be effective and not poor. The purpose of light is most important, because without light the things have no appearance, no colour, no shape and no perspective. Light and colour affect human efficiency, accident-possibility and his general well-being, morale and fatigue. Medical research has proved that a sufficient amount of light is needed for the healthy physiological functioning of human organism. Light regulates various physiological functions within the body and poor light adversely affect the health.. Benefits of good lighting are also direct and manifold, because, it affects our sight as well as the object to be seen. It helps in two ways, by better seeing for work performance and better environment. Better seeing condition causes better discrimination, concentration, alertness and less fatigue. Better discrimination causes less spoilage and quick fault detection. Greater concentration causes better work. Less fatigue allows greater output and greater production. Better environment produces better morale,. comfort, supervision and interest. All these factors cause better ability to perceive objects and keep a clear view of all details, of better conservation of energy and material, reduced labour turnover, better housekeeping, more production with less waste of material, energy and labour, prevention of eye strain and accidents, increased accuracy, efficiency, productivity, speed of seeing and reading and improvement in health and safety of work-people. It is most useful to elderly people. 2.2 Effects of Bad or Poor Lighting: Effects of bad lighting are direct and manifold, because, it affects our sight or visual perception. Bad light causes glare, shadows, darkness, eye strain, restricted vision, fatigue, headache, slower reaction and greater susceptibility to error and accident and lower output. Accidents during night are obvious due to bad or insufficient lighting. Therefore, need of light is basic and essentially required to work better, to avoid eye strain and to reduce accidents. Gloomy, dirty and poorly lighted workplaces cause depression. Poor lighting causes great hardship e.g. difficulty in reading micrometer, making fine adjustment, passing a thread in needle and the like. Conversely, well lighted workplace looks delightful and encourages to work. Poor lighting requires more time to see or distinguish object. Glare and shadows cause eye-strain resulting in more chances of accidents. Therefore to increase safety, prescribed standard of illumination is the basic (minimum) working condition. See part 4 for Standards. 2.3 Increase of Safety arid Productivity due to Good Lighting : Good lighting includes both, day lighting and artificial lighting and they should be in the requisite proportion. The spectral composition of light and colour layout should be appropriate to gain their maximum advantages. Good light decreases accident and increases work quality and quantity, productivity and promotes better health and morale of all work-people. In industry, therefore, it is the duty of lighting engineer to consider this basic need and to provide good seeing conditions to„ avoid accidents due to visual disorder. Planning from the design stage will help much. Good lighting makes the worker more alert and enables him to concentrate and use better discrimination which result in less spoilage, less rejects, fast fault detection, better work and ultimately in Safety. Fundamentals of Industrial Safety and Health 9- 3 Lighting and Colour  The specified result improvements (in quantity and quality) were the outcome of the combined effect of the improvement in the primary visual functions (vision acuity, contrast sensitivity, depth and colour distinction etc.) and light dependent increase in psychological and physiological activation. Emergency lighting should be provided where power failure is frequent and no natural lighting is possible due to absence of windows etc. 3 PRINCIPLES OF ILLUMINATION 3.1 Definitions : Light is the electromagnetic visible radiation (waves) Within the range of 380 to 760 nanometres (I nm = 10-9 m) or 7.5 x 1014 to 4.3 x 1014 hertz (Hz). The optical spectra, the luminous (electromagnetic) radiation capable of inducing visual sensation through the eye within the range of wavelengths from 10 to 340000 nm, can be divided, depending on wavelengths, into the ultra-violet region (from 10 to 380 nm), the visible region i.e. light (from 380 to 760 nm), and the infrared region (from 760 to 340000 nm). In the visible region, colours from violet (380 nm) to red (760 nm) are recognisably visible. The sensation of colour is also associated with the radiation wavelength. Luminous radiation exerts certain influence on the nervous system, pulse rate, intensity of certain metabolic reactions and the psychological state of man. For a rational or an adequate lighting, the quantity and quality of illumination, both are essential. Some basic concepts, units and symbols are as follows : (A) Luminaire is a complete lighting unit including the lamp, globe, reflector, refractor, housing and support that is integral with the housing. (B) Luminous (or light) flux is the quantity of light emitted per second by a light source. It is the radiant power or luminous flux i.e. rate of propagation of radiant energy evaluated by the eye. Its unit is lumen (1m) and the symbol F. (C) Luminous Intensity is the luminous flux emitted per unit of solid angle (the measure of spatial density of the light flux) in a given direction. Its unit is candela (cd) and the symbol 1 and 1 = F/w, where w is the solid angle. (D) Illuminance or Illumination is the luminous flux that strikes a unit area i.e. it is the surface (E) density of the light flux distributed uniformly over the surface. Its unit is lux (lx) which is equivalent to 1 lm/2 and the symbol E, E = F/ S, where S is the surface area. When calculating artificial illumination of industrial premises, the concept of mean illuminance usually applies to a horizontal plane 0.8 m above the floor level, also known as the workplace plane. Old unit of illuminance was foot-candle which is the number of lumens/ft2 or 1m/ft2. New unit is lux which is 1 lm/2. Their relation is-. 1 foot candle.= I Im/ft2 == 10.76 lux (or meter candle or 1m/2 ) 1 meter candle = 1 lux = 0.092 foot candle Daylight Factor (DF) = lux/80 Illuminance level is a prescribed amount Illuminance. Initial illuminance is the amount of illuminance obtained when the luminaries are neat and clean and when the lamps are first energized. Fundamentals of Industrial Safety and Health 9- 5 Lighting and Colour  Service or maintained illuminance is the mean or average illuminance throughout the life of a lighting installation or over an extened period of time. This is lower than the initial illuminance for several reasons stated below. Light loss factor is a factor which represents the average-to-initial illuminance ratio of a lighting system. It represents the depreciation and deterioration of a lighting system caused by following reasons: 1. Loss of lamp lumens due to aging effect. 2. Decrease in lamp and luminaire output resulting from dust, dirt, insects and chemical changes in the luminaire reflecting surface. 3. Increased absorption of the light output of the luminaries by dust, dirt and chemical changes in the room reflecting surfaces. 4. Differences between actual and design lamp voltages. Standard illuminance is the service illuminance recommended for standard conditions. Coefficient of reflection or Reflection factor is the ratio of the light reflected by the body to the incident light. Its symbol is ‘r’. Coefficient of Utilization, or Utilization factor is the total flux received by a surface divided by the total flux from the lamps illuminating it. Seeing or visual task is the object being regarded and its background. Mounting height is the distance from the bottom of the luminaire to the surface used as a reference. (E) Luminance (Brightness) is the luminous flux (directly seen by the eye) reflected by a surface in a given direction. Its unit is candela per sq. m. (cd/m?), and the symbol L. All other conditions being equal, the luminance is proportional to the illuminance i.e. L = lr/s, where r is the reflection factor of the surface, and is given by r = Fref/Ffal where Fref = luminous flux reflected from a surface and Ffal = luminous flux falling on that surface. It is also known as coefficient of reflection. (F) Background is the surrounding surface, real or artificial, against which the object can be visualised or discerned. The background is said to be light if the reflection factor is greater than 0.4, semi-dark, if it is 0.4-0.2 and dark, if less than 0.2. Normal background is the surface behind object. (G) Contrast is the relative luminance between an object and its background (e.g. a letter on paper) and its symbol is C. Where the background has aluminance L and the object a luminance L (L„>L,), it can be expressed C = (L1-L2)/L~. Contrast is a dimensionless magnitude ranging between 0 and 1. It may be high, soft or low. (B) to (E) are quantitative and (F) & (G) are qualitative indices of illumination. Digital light meter (photocell device) is available to measure light directly in lux. For sufficient lighting, lighting level should be measured by lux (light) meter and than it should be compared with the standard lux level given in Part 4. See Part 6.4 for figure. Fundamentals of Industrial Safety and Health 9- 6 Lighting and Colour 3.2 General Principles of Good Lighting: General Principles or requirements of good lighting are as follows : 1. Adequate illumination. 2. Avoidance of glare. 3. Avoidance of shadow. 4. Uniform lighting. 5. Appropriate contrast. 6. Appropriate colour contrast. 7. Colour effect and 8. Avoidance of flicker and stroboscopic effect. These are briefly explained below : See also part 6 for details of design principles 3.2.1. Adequate Illumination : Adequate, rational or good illumination needs sufficient quantity of illumination necessary for avoiding discomfort to the worker and undue strain on eyes- The quantity or intensity of illumination is given by luminous flux, luminous intensity, illuminance, luminance and reflection factor as explained in the foregoing part 3.1. Its requirement varies from place to place, person to person and with the age of person also. Therefore by experiments, standards of illumination are recommended for a variety of places and jobs to have sufficient quantity of light for better work performance. Such statutory standards and Indian standards are separately given in part 4 of this Chapter. Visual acuity (sharpness of vision) increases with light intensity and is about equal to daylight acuity as 1000 lux is approached. However, this degree of acuity is seldom required and it is apparent that the desired amount of lighting will vary with the amount of detail required in the work. For example, for very fine work like distinguishing black thread on black cloth, intensity of 2000 lux is required but for exit road, car parking, storage area 20 lux is required. Although individuals differ in amount of light they find most desirable, 65% of the subjects of one study judged intensity between 10 to 30 foot-candles or 100 to 300 lux, the most comfortable for reading. The quality of illumination depends on three factors - diffusion, distribution and colour value. Regardless of the quantity of illumination, its effects may be impaired because of the unevenness, the glare or the faulty direction of the light. Diffusion is the breaking up of a beam of light and the spreading of its rays in many directions by a surface. It is the process of reflection of -light by a reflecting surface or of transmission of light through a translucent material. Thus adequate illumination requires sufficient quantity and good quality of light necessary for the work. See Part 3.2.4 for uniform lighting. Fundamentals of Industrial Safety and Health 9- 7 Lighting and Colour 3.2.2 Glare : Glare is the condition in which brightness or the contrast of brightness interferes with vision. Glare is produced by excessive light stimuli i.e. excessive luminance in the field of vision which disturbs the adaptation process of retina. Sometimes glare impairs the visual function, of the eye and reduces visual performance. Glare causes discomfort, annoyance, eye fatigue and impairment of or interference with vision. It is produced by excessive light stimuli i.e. too much light which affects the adaptation process of the retina. It can be considered at three levels.(types)- (1) Direct or disability glare (2) Discomfort glare and (3) Indirect or reflected glare. Direct or disability glare comes directly from the light source to the eye and impairs the ability to see clearly (e.g. dash on upward headlight of a car). This is due to excessive light focused on the eye and scattering of light inside the eye. It depends for its effects upon the position of the light source in the field of view and on the contrast in brightness between the light source and its background. It can be avoided by: 1. Provide diffuser over the lamp or reflector (screen) with minimum reflecting angle 20° below the horizontal, (dipper) 2. Reducing the brightness of the light source (e.g. by enclosing the lamp in bowl reflector). 3. Reducing the area of high brightness (e.g. by installing louvers below the light source). 4. Increasing the angle between the' source of glare and the line of vision i.e. by increasing the mounting height. 5. Decreasing the source of glare so as to lessen the contrast. Discomfort glare is due to liberal (less) or bright (more) light. It causes visual discomfort without necessarily impairing the ability to see and may occur from unscreened windows in bright sunlight or when over-bright or unshaded lamps in the workroom are too strong in brightness for the workroom environment. Reflected glare is glare that comes to the eyes as glint (flash) or reflection of the light source from some polished or shining surface. It is caused by a mirror image of the bright light sources reflected from shiny or wet workplaces such as glass or plated metal. These reflections distract or distort attention, make important detail difficult to see and reduce contrast or cause acute discomfort. It can be avoided by: 1. Changing the shining finish by matt finish. 2. Changing the task position or its surrounding. 3. Using light source of low brightness or providing lamp shade. 4. Arranging the geometry of the installation so that there is no glint at the particular viewing direction, e.g. increasing the source height. Fundamentals of Industrial Safety and Health 9- 8 Lighting and Colour 5. Providing supplementary lighting. 6. Painting walls and ceiling with light colour so that surrounding becomes bright. 7. Increasing brightness to reduce relative brightness of the glare. Rule 32 of the Gujarat Factories Rules prescribes, for the purpose of prevention of glare, that where any lighting source is less than 5 mt above floor level, no part of that light having brightness greater than 5 lamberts (1.5 foot candles=16 lux) shall be visible to persons normally working within 30 mt from that source, except where the angle of elevation from the eye to that source exceeds 20°. It is also suggested that local light (lamp on the job) shall be provided with opaque shade or effective screen to prevent glare in the eyes of workers working nearby. Values of limiting glare index along with average illumination lux value are given in IS:6665 and Appendix D, Part 4 of National Electric Code. 3.2.3 Shadow : Shadow affects the amount of illumination and is caused not by poor lighting but - by fixing light sources too wide apart or in wrong positions so that light is obstructed by some object. Light (faint) shadow may be allowed but dark (dense) shadow that conceals hazard or indicates wrong thing is not desirable, as it may cause accident. Shadow on staircase, near door for entry or exit, near tool rack or on the work (job) table is not at all desirable and must be removed by providing extra or local light or shifting the light source or the object causing shadow. Harsh shadows should be avoided, but some shadow effect may be desirable from the general lighting system to make more noticeable the depth and form o~ object. There are few specific visual tasks where clearly defined shadows improve visibility and such effects should be provided by supplementary lighting equipment arranged for the particular task. 3.2.4 Uniform Lighting : The human eye can clearly perceive differences in luminance of over 50%. It takes time to adopt sudden variation in the intensity of lighting, particularly from higher to lower intensity. Uniform distribution of lighting is desirable. Distribution of light requires two problems to solve (1) uniformity of illummation and (2) elimination of shadows. In uniform lighting, the distribution of light with a maximum and minimum illumination at any point should not be more than one-sixth above or below the average level in the area. Indirect lighting is the best method for producing uniform illummation. Here all the usable light is reflected light, high points of light from the bulb striking the eye directly are out of the visual field. The disadvantage of indirect light is its cost, since considerable light is lost through absorption. However its benefit is more worth than its extra cost. 3.2.5 Contrast: Fundamentals of Industrial Safety and Health 9- 9 Lighting and Colour  The ability to see detail depends upon the contrast between the detail and its background. The greater the contrast, difference in luminance, the more readily the seeing task is performed. The eyes function most comfortably and efficiently when the luminance within the remainder of the environment is relatively uniform. Therefore all luminance in the field of view should be carefully controlled. 15:3646 (Part I & II) provide details for this. Reflectance should be maintained as near as practical to recommended values (For ceiling 80 to 90%, for walls 40 to 60%, for desks and bench tops, machine and equipment 25 to 45% and for floors not less than 20%). High reflectance surfaces are desirable to provide the recommended luminance relationship and high utilisation of light. They improve the appearance of the work place. It is also desirable that the background should be slightly darker or paler than the seeing task. Too much contrast is not desirable. The contrast recognises the object easily and increases visual performance. If the difference between the object (job or seeing task) and its background is not noticeable, it is difficult to work. A black machine in black background (darkness) is difficult to notice. There should be a minimum contrast between the visual target detail and its background. The differences in luminance of visual task, its immediate background and environment should not exceed certain maximum values i.e. a relationship of 10: 3:1 for normal tasks and 10 : 5 : I and 10 : 10 : I for precision work. 3.2.6 Colour Contrast: Eye sees an object by the light it reflects and distinguishes its details mainly by colour contrast. Thus, in addition to luminance contrast, colour contrast may be influenced by the choice of the colour of light. The choice of the correct colour of light depends on the task to be performed and the requirements to be met by vision. It may be noted that there must not only be adequate illumination to see an object clearly, but also the object must be visible in its surroundings. It must have moderate colour contrast. The colour approximating to white will give better colour rendering and light yield. The colour approximating to red will give low Quality colour rendering but the light will create an emotional atmosphere. A well painted machine inspires a feeling of personal pride and proper maintenance is encouraged. 3.2.7 Colour Effect: It refers to the appearance of coloured objects when illuminated by a particular light source. It is the property of light which facilitates the perception of surface colours and depends on the spectral composition of the light. For example, red surface will appear red only, if the light falling on it contains red, but it will appear brown under the yellow of sodium street lighting. The maximum value of the index is 100 and at this value there is no shift, i.e. the colour rendering is perfect. For example, an incandescent tungsten filament lamp has a colour rendering index of 100, fluorescent tubes between 55 to 95, mercury vapour lamps approximately 45 and low-pressure sodium vapour lamps less than 25. Where colour discrimination and colour matching are a part of the work process, the light source selected should have the desired colour rendering properties.. 3.2.8 Flicker and Stroboscopic Effect : All lamps working on alternating current give light which pulsates at twice the supply frequency. This type of discontinuous light of almost all frequencies can produce (fleshing rapidly to show moving object stationary) effect, in which a rotating or reciprocating object can appear to be stationary, or moving slowly, or even appear to be rotating in the opposite direction etc. This false belief can cause accidents in the industrial situation. It is a real hazard in the presence of moving machinery. High Fundamentals of Industrial Safety and Health 9- 10 Lighting and Colour intensity discharge lamps and fluorescent tubes have some 'flicker content in their light output at twice the mains frequency. The steps to diminish the stroboscopic effect are: 1. Light the moving object with lamps fed from two different out of phase a.c. supplies, or from two or three phases of a three-phase supply or lead lag luminaries. 2. Select a lamp with a low flicker characteristic, e.g. a fluorescent coated high-intensity discharge tungsten filament (GLS) lamp or ordinary filament lamp. 3. Add a local GLS lamp to augment the general lighting. 4. Use GLS or tungsten halogen lamps fed from a direct current (d.c.) supply. 5. Use the common twin-tube circuit. 4 RECOMMENDED STANDARDS OF ILLUMINATION It is not a simple matter to specify suitable intensity levels based upon sound reasoning. As there is no fixed threshold level of illumination below which a visual task is greatly impeded, some compromise has to be made between an ideal level and adequate level. Generally a recommended level is arrived at after careful consideration of eyesight, the visual task, the environment and the economy involved. Any specification is therefore, opens to controversy, the recommended level, however, serves chiefly as a guide to good practices. Standard illumination benefits people with normal sight and helps to faulty vision. It can be achieved through a combined usage of day lighting and artificial lighting and maintained by proper cleaning and re-lamping etc. Importance of illumination level: Illumination, noise, temperature and other environmental conditions such as chemical exposure and vibration play an important role in the ability of humans to interact effectively with equipment or a system. Lighting is an important element in the design of any system as improper lighting levels may cause system elements to be seen incorrectly or not seen at all. Improper-illumination level may result in the eye strain, muscle fatigue, headache or accidents. The adequacy of lighting depends upon the type of lighting provided, its quality and quantity, the age of the worker and visual requirements of the task or system. Illuminance ranges Circumstances may be significantly different for difficult interiors used for the same application or different conditions for the same kind of activity. A range of illuminance is recommended for each type of interior or activity. Each range consists of three successive steps of the recommended scale of illuminance. Middle value of each range, represents the recommended service illuminance that would be used unless one or more of the factors mentioned below apply. Higher value of the range should be used when: 1. Unusually low reflectance or contrasts are present in the task. 2. Errors are costly to rectify. 3. Visual work is critical. Fundamentals of Industrial Safety and Health 9- 11 Lighting and Colour 4. Accuracy or higher productivity is of great importance. 5. The visual capacity of the worker makes it necessary. The lower value of the range should be used when: 1. Reflectance or contrasts are unusually high. 2. Speed and accuracy is not important. 3. The task is executed only occasionally. Depending upon importance of the work, illumination level must be according to the standards mentioned below. 4.1 Statutory Provisions : Section-17 of the Factories Act requires sufficient and suitable lighting, natural, artificial or both and prevention of direct or reflected glare and shadows causing eye strain or risk of accident. Rules 30 to 34 of the Gujarat Factories Rules prescribe further details. General level of 30 meters candles (30 lux) or more at the horizontal level of 91.4 cm (3 feet) above the floor is prescribed. Where the light source is above 7.6 meter height from the floor, at least 10 meters candle minimum illumination should be available. It should be at least 30 meters-candles (30 lux) where the work is actually going on. Walkways require at least 5 meter candles (5 lux) at floor level. Rule 32 describes details to prevent glare, (see Part 3.2.2) Minimum illumination levels prescribed by Rule 35 of the Maharashtra Factories Rules is given in Table 9.2 Table 9.2 : Minimum Illumination Levels u/r 35 MFR S. Area / Workroom Minimum Intensity of No. Illumination in Lux 1 Stock-yards : main entrance and exit roads, cat-walks of 20 outdoor plants, coal unloading and storage areas. 2 Passage-ways, corridors and stairways, warehouses, stock' 50 rooms for large & bulky materials, platforms of outdoor plants, basements. 3 Engine and boiler rooms, passengers and freight 100 elevators, conveyor crating & boxing departments, storerooms for medium and fine materials, locker rooms, toilet and wash-rooms. 4 Where discrimination of detail is not essential (e.g. handling 50 of material of coarse nature, rough sorting, handling coal or ashes etc.) 5 Where slight discrimination of detail is essential [e.g. 100 production of semi-finished iron and steel products, rough ; assembling, opening, carding drawing, spinning (ordinary) counts of cotton]. 6 Where moderate discrimination of details is essential (e.g. 200 medium assembling, rough bench work and machine work, inspection and testing of products, canning, sawing, sewing of light coloured textiles and leather products, weaving light Fundamentals of Industrial Safety and Health 9- 12 Lighting and Colour  thread, warping, spinning fine counts). 7 Where close discrimination of S detail is essential (e.g. 300 medium bench and machine work, fine testing,.flour grading, leather finishing, weaving cotton goods or light coloured woollen goods, welding sub-assembly, drilling, rivetting, book-binding and folding ). 8 Where discrimination of fine detail is involved under a fair 500 degree of contrast for long periods of time (e.g. fine assembling, fine bench and machine work, fine inspection, fine polishing and bevelling of glass, fine wood working, weaving dark coloured woollen goods). 9 Where discrimination of extremely fine detail is involved 1000 under conditions of extremely poor contrast for long periods of time. (e.g. extra fine assembling, extra fine inspection, jewellery and watch manufacturing, grading and working of tobacco products, dark cloth hand tailoring, final perching in dye works, make-up and proof-reading in printing plants). 4.2 Indian Standards : SP 32 a Handbook on functional requirements of industrial buildings (lighting & ventilation) may be referred. Some useful IS are given in Table 9.3 : Table 9.3 : Indian Standards on Lighting S. Area / Workroom Minimum Intensity of No. Illumination in Lux 1 Industrial lighting 6665 2 Day lighting of factory buildings 6060 3 Day lighting of buildings 2440 4 Principles of good lighting and aspects of design (Part I) 3646 5 Schedule for values of illumination and glare index (Part II) 3646 6 Calculation of coefficient of utilization by the BZ method 3646 (Part III) 7 Eletro technical vocabulary Part 16 1885 8 Flameproof electric lighting fittings 2206 9 Dust – proof electric lighting fittings 4012 10 Dust-tight electric lighting fittings 4013 11 Miners’ Cap-lamps 2596 Out of 63 types of industrial buildings and processes, only 15 are selected from Table-2 of 15:6665 and given in Table 9.4 as a sample recommendation. Table 9.4 : Recommended Values of Illumination (IS : 6665) S. Industrial buildings and processes Average Illumination No. Lux 1 General Factory Areas: a Canteens 150 b Cloakrooms, Entrances, Corridors & Stairs 100 2 Factory Outdoor Areas: Fundamentals of Industrial Safety and Health 9- 13 Lighting and Colour devices are offered for 50-watt to ISO-watt high-pressure sodium lamps. Power factors range from 40 percent to 99 percent depending on the heavy type and the age of the lamp. Lamp life is 24,000 hours. Metal halide lamps are similar in construction to mercury vapour lamps. The difference is that metal halides are added to the mercury and argon in the arc tube. The efficacies are improved to the range of 75 lumens per watt to 125 lumens per watt, excluding ballast loss. The colour rendering is quite white and is usually superior to the phosphor-coated mercury vapour lamp. The warm-up time for metal halide lamps is 2 minutes to 4 minutes, and re-strike time varies from 5 minutes to 15 minutes, depending on the type. Power factors in the range of 90 percent can be obtained. Lamp life varies from 3000 hours to 20,000 hours. Metal halide lamps have more rapid lumen depreciation than do mercury vapour lamps and have high surface operating temperature which must be. considered before application in classified locations. The lamp life and lumen output are affected by burning position. Compared with incandescent lamps, mercury vapour lamps offer the advantages of longer average life and higher lumen output; however, with the advent of metal halide and high pressure sodium lamps, the mercury vapour lamp is considered by many to be obsolete, except in existing plants.having similar lamps. The mercury vapour lamp is considered obsolete because of its rapid lumen depreciation and low lumens-per-watt characteristics. Mercury vapour, or mercury-halide lamps, tubular fluorescent and sodium vapour lamps are generally called 'electric discharge lamps' as electric current is passed through certain gases to produce emission of light. From above types the mercury vapour lamps take up to 6 minutes and sodium vapour lamps take up to 20 minutes to reach their maximum output, the actual time will be determined by the wattage of the lamps. In the event of a power failure, restoration of power will immediately start machinery, while discharge lamps would take 'warming time' to relight. This time gap may cause accident due to insufficient lighting. To avoid such situation emergency lighting is a must which will glow during power absence. Selection of the type of light source depends on efficiency, installation, running costs, maintenance, life characteristics, size, robustness and heat & colour output. The efficiency of any lamp is the light output per unit of electricity consumed and is measured in lumens per watt. For example, it is as under: Type of Lamp Lumnes per watt (approx.) Incandescent lamps 15 Tungsten halogen 22 High pressure mercury 35-55 Fluorescent lamps 75-95 High pressure sodium 100 Incandescent lamps are cheaper but they are more expensive than other types of lamps to run and they require frequent replacement. Discharge and fluorescent lamps cost more to install but their greater efficiencies and longer life make them more suitable for general interior lighting. Where colour performance is important, the tubular fluorescent lamp is more suitable and not the mercury or sodium vapour lamp. Where lighting is required at height (e.g. overhead crane in workshop) the high pressure discharge lamps are more suitable. Where artificial lighting is supplied, hazards of electricity must be identified and removed. Loose wiring, faulty switches or fuses, un-insulated wire or cable, open switch box, open wire in plug, many Fundamentals of Industrial Safety and Health 9- 20 Lighting and Colour 4. Improve quality of workmanship and normal skill. 5. Improve labour morale and interest in work. 6. Reduce accidents and increase safety. 7. Reduce 'rejects'. 8. Reduce absenteeism. 9. Raise standard of good housekeeping.. 10. Improve building and machinery maintenance. 11. Reduce hidden costs of dull and gloomy atmosphere, and 12. Improve overall psychological and physiological effects on workers for better work performance. 7.2 Reflection Factors (LRV) : A surface reflects light. The amount of light reflected will depend on the colour scheme of the surface. Pure white will reflect 100% and pure black 0% of light falling on them and reflections factor of other colours will fall in between. The recommended reflection factors, also known as light reflectance value (LRV), for interiors are : Part Colour LRV Ceiling White 80-90% Walls Light colour 50-75% Furniture, equipment, machinery, Light to medium colours 30-50% desk etc. Floors Medium to dark colours 15-30% Light reflectance values (LRV) of some colours are as follows : Colour Percentage of reflected light White 85 to 90 Yellow Light 75 medium 65 Grey Light 75 medium 55 dark 30 Green Light 65 medium 52 dark 7 Blue Light 55 medium 35 dark 8 Ivory Light 77 over green or white stippled 40 Cream Light 66 Buff Light 56 Brown Dark 10 Appropriate colour should be selected from above two tables which conclude that ceilings and walls should have light colours for more reflection and floors, furniture and equipment should have medium to dark colours for less reflection. Colour can be used as a factor to reflect light to increase it. 7.3 Colour Code and Safety : 7.3.1 Indian Standards : IS to be followed are : Code of practice for safety colours and safety signs 9457, Pipelines, identification, colour code 2379, Standard colours for building and decorative finishes 1650, pipelines in thermal power plants 9404, Identification for canisters and cartridges 8318 and Gas cylinders and related medical equipment 3933. 7.3.2 Colours to Identify Hazards : Fundamentals of Industrial Safety and Health 9- 28 Lighting and Colour  Colour coding is most desirable and useful for safety purposes. Standard colours are used to identify hazards as follows : Red - Fire protection, prohibition, danger, emergency stops on machines, red cross on medical facilities. Yellow - Risk, danger or caution, hazards of slipping, falling, striking etc., flammable liquid storage, yellow band on safety cans, material handling equipment viz. lift trucks, cranes, crane hooks, caution, transport equipment, obstructions, change in floor level, stair nosing etc. Green - Safety equipment not identified elsewhere, safety board, safe condition. Blue - Warning and information signs, bulletin boards, rail road uses. It indicates safety colour only if used with a circular sign. Orange - Dangerous parts of machines or energized equipment such as exposed edges of cutting devices, inside of movable guards, enclosure doors, transmission guards, electric installations. Purple - Radiation Hazards Black & White - Housekeeping and traffic markings. Also used as contrast colours. White is a contrast colour for red, green and blue. Black is a contrast colour for yellow. The piping in a plant may carry harmless or hazardous contents. Therefore it is highly desirable to identify them. Some standard colour coding is as follows: Content in the piping Colour Flammable or water for fire protection Red Dangerous (hazardous chemical) Yellow Safe (water, air) Green Protective material (inert gas) Blue The proper colour may be applied to the entire length of the pipe or in bands 20-25 cm wide near valves, pumps and at repeated intervals along the line. The name of the specific material should be stencilled in black at readily visible locations such as valves and pumps. Piping less than 3/4 inch diameter is identified by enamel on metal tags. Anti-resistant colours should be used where acids and other chemicals may affect the paints. Following colour coding is also useful in identifying pipelines (IS:2379): S. No. Material Colour 1. Water Sea green 2. Steam Aluminum, IS 2339 3. Air Sky blue 4. Acids Dark violet 5. Alkalis Smoke grey 6. Gases Canary Yellow 7. Hydrocarbons/ organic compounds Dark admirality grey 8. Mineral, vegetable and animal oils, combustible liduids. Light Brown 9. Other liquids / gases which do not need identification Black Fundamentals of Industrial Safety and Health 9- 29 Lighting and Colour  Entire length or a portion, more than 30 cm, of a pipeline should be painted so that it should not be mistaken for a colour band. The colour bands are superimposed on the ground colour, applied at start, near valves, joints, bends and end points. For a longer pipe, interval may be 50 m. Minimum width of colour band should be as under : See Part 8.4 & 13.1(4) of Chapter-18 for colours of gas cylinders and pipe lines. 7.3.3 Accident Prevention Signs : Accident prevention signs arc most widely used safety measures in industry. Their uniformity in the colour and design of sign are essential. Employees may be unable to read English or may be colour- blind and yet react correctly to standard sign. Following colours are normally used for signs :- Sign Colour Danger Red oval in top panel; back or red lettering in lower Immediate and grave danger or peril. panel. Caution Yellow background colours; black lettering. Against lesser hazards. General Safety Green background on upper panel; black or green lettering on lower panel. Fire and Emergency White letter on red background. Optional for lower panel; red on white background. Information Blue for bulletin boards. In-plant Vehicle Traffic Standard highway signs. Exit Marking See Life Safety Code, NFPA 101, Section 5-10. Different types of Accident prevention signs are shown in fig. 9.1. See Fig. 18.1 in Chapter 18 also. 7.3.4 Painting of Plant and Machinery : No lighting scheme can be fully effective unless well-chosen (and well-maintained) finishes are provided on main interior surfaces such as ceilings, walls, plant and equipment. The main object is to use colours which will reflect rather than absorb light. Diffused light thrown back in this way can contribute substantially to the total illumination on the work. It also improves the quality of the lighting by softening shadows and minimising harsh contrasts in the field of view, thus contributing to visual comfort and efficiency. Because of full reflection of light, to paint the plant and everything by white colour is not advisable, because 'only white'.premises and equipment cause fatigue and boredom and are no incentive for active or creative work if there is no combination of other colours. Any extreme should also be avoided. For ceilings, the reflection factor should be at least 75% which means white or near-white. A matt finish is preferable.. Aluminium paint is not recommended. Walls are best finished in light pastel colours in the 50-75% range, except in the case of very brightly lit walls (e.g. those adjacent to a large window) which may need toning down to 40% or less to prevent them from becoming too glaring. Conversely, walls containing windows (but which receive no direct light themselves) cannot often be painted white with advantage. Fundamentals of Industrial Safety and Health 9- 30 Lighting and Colour  Fig. 9.1 Accident Prevention Signs : (a) Prohibitory (b) Warning (c) Mandatory (Legal) (d) Safe Condition 7.4 Psychological Effects of Colour : They are as follows : Colour & other parameter Psychological Effects Red Stimulates, activates, energises Yellow Bright, Gray, Fresh like sunshine Orange Tension producing Light Green Relaxed feeling, improve morale Light Blue Purple Feeling of depression Fundamentals of Industrial Safety and Health 9- 32 Lighting and Colour  White Stimulating if it is used with warm colours Black Not depressing if it is used with other colours Size Green and Blue objects look larger than Yellow and Red Space Green and Blue surfaces record. Red and Yellow come forward. Temperature Red and Yellow give warm feeling. Blue and Green give cool feeling. Weight Bright colours make objects look lighter. Red, orange and yellow (light) are warm colours. Blue, turquoise and green are cool colours. Off- whites and pastel tints are light colours. Black, grey and deep tones are dark colours and red, yellow, yellow green, orange and red-orange are considered bright colours. Warm colours may be used to obtain activation and relaxation effects i.e. energy input. Cool colours are aid to energy output. Bright colours give an impression of useful place and lightness and produce calm and peaceful effect. Dark colours may have a cheerless and depressing effect. In selecting colours following guideline is useful - 1. Natural white or light colours are safe and render all colour shades in true proportions. 2. Cool colours on objects give good effect. Therefore they are called safe object colours. 3. Bright colours should 'be preferred as background colours. More saturated richer colours should be preferred for objects. The sensation of colour of an object depends on the colour of the background. 4. Sources emitting warm colour of light, render warm colours of objects. The proportion of short- wave radiation makes cold colours ineffective. 5. Yellow seen against a black background will be luminous but will loose its luminosity when seen against white. This effect (simultaneous contrast) is true with all colours and shades. 6. When seen against black, every colour becomes brighter and against white paler. This is called successive contrast. 7. Colours can affect their background also (Bezoll's effect). These rules emphasise importance of and interaction between light and colour. The appropriate light has to be chosen with colour and vice versa. While designing colour schemes for plant and equipment, these factors are to be taken into consideration. This discussion concludes t1iat the question of colour may not just be left to the painter, nor the question of light to the electrician. Scientific knowledge of combined effects of lighting and colour should be properly utilised. Colour liking may change with time and fashion but safety aspect should not be forgotten. Fundamentals of Industrial Safety and Health 9- 33 Lighting and Colour