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OCCUPATIONAL SAFETY AND HEALTH
Lighting. Occupational Safety and Health
Occupational Safety and Health / Legislative basis for labor protection Almost all information from the outside world a person receives with the help of vision. Therefore the role lights and colors for human activity is enormous. The perception of light is an essential element of our ability to act, as it allows us to evaluate the location, shape and color of objects around us. All the bodies and objects around us are divided into luminous and non-luminous. Luminous natural and artificial bodies emit electromagnetic radiation with different wavelengths, but only radiation with a wavelength of 380 to 780 nm makes us feel light and color. Therefore, light is a characteristic of a light stimulus that creates a certain visual sensation, and radiation of a specified wavelength range is called the visible part of the spectrum. When the eye is exposed to radiation with a wavelength of less than 380 nm (infrared radiation) and more than 780 nm (ultraviolet radiation), light and color sensations do not occur. All radiations are divided into two types: monochromatic and complex. Monochromatic radiation is radiation of any one wavelength. Complex radiations consist of several monochromatic, up to all radiations of the visible part of the spectrum. If a body emits a luminous flux containing all radiations from 380 to 780 nm, and, moreover, the power of these radiations is the same, the color of this body is perceived as white. Passing white light through a prism, it can be decomposed into a spectrum of monochromatic radiation, which causes sensations of various colors, from red to violet. If we divide the entire variety of spectral colors we see into seven groups, then we get a series: red - orange - yellow - green - blue - blue - violet. The division of the spectrum into seven color zones is purely arbitrary, since the eye distinguishes in the spectrum a huge number of intermediate shades of a continuous sequence of colors in the spectrum. The vast majority of objects around us do not have their own glow. They do not emit their own light, and we can see them only in the light reflected by them. All colors are divided into two groups: achromatic and chromatic. Achromatic colors include white, gray and black. All other colors are chromatic. Every luminous object radiates energy, which in the form of electromagnetic waves propagates in different directions. To assess the visual perception of the flow of light energy, the following concepts are used: "luminous flux", "light intensity", "brightness", "illuminance". The luminous flux is the flux of light energy, estimated by its effect on the human eye. The power of light is called the spatial density of the light flux, i.e. the ratio of the luminous flux of a point light source to the value of the solid angle in which this flux propagates. Brightness (or photometric brightness) is the intensity of light in a certain direction (into the observer's eye) per unit area of the visible luminous surface located perpendicular to the direction of light propagation. Illumination is called the surface density of the light flux, i.e. luminous flux per unit area of the illuminated surface. Contrast is the difference between the brightness of the observed object and its environment (background) or between different parts of the object. Achromatic colors are characterized by the reflection coefficient, i.e. ratio of reflected light to incident light. Chromatic colors are characterized by three colorimetric quantities: color tone (dominant wavelength), color purity (saturation), and brightness or lightness. Brightness is determined to characterize the color of luminous bodies, lightness (or relative brightness) - to characterize the color of non-luminous bodies. For monochromatic radiation, the hue is the wavelength of the radiation it emits. The functions of vision that are especially necessary for safety and productivity of work include: contrast sensitivity, visual acuity, speed of distinguishing details, stability of clear vision, color sensitivity. The ability of the eye to distinguish between the minimum values of the difference between the brightness of an object (detail) and the background is called contrast (distinctive) sensitivity. The dependence of the contrast sensitivity on the illumination conditions of the object and the brightness to which the eye has adapted to the maximum has been established. Visual acuity is the maximum ability to distinguish individual objects. The normal eye can distinguish between two points seen at an angle of 1о. Illumination has a great influence on visual acuity. With an increase in illumination to a certain level, visual acuity also increases. A certain role in the performance of visual work belongs to such a visual function as color perception. The value of this function increases when performing production operations related to the need for color discrimination. The most favorable conditions for color perception are created under natural (solar) lighting (since it is large enough), as well as under artificial lighting with color-corrected fluorescent lamps. An important role in the distinction is played by color contrast. Blue on a white background, black on a yellow background, and red on a white background have the greatest contrast. Therefore, the prohibition sign of traffic lights is associated with red, and security fences are made with a black and yellow zebra. The same colors are also used on warning signs. For successful visual work in conditions of variability of illumination, the so-called visual adaptation is of great importance, i.e. adaptation of the eye to light conditions. Thanks to the adaptation process, the visual analyzer has the ability to work in a wide range of illumination. There are light and dark adaptations. Light adaptation is the adaptation of the eye to work in conditions of high brightness of the field of view. Light adaptation with increasing brightness in the field of view occurs quickly - within 5-10 minutes; dark adaptation - adaptation of the eye to lower brightnesses of the visual field - develops more slowly (from 30 minutes to 2 hours). The process of adaptation is accompanied by photochemical and nervous processes, restructuring of receptive fields in the retina, changes in pupil diameter (pupillary reflex). Frequent changes in brightness levels lead to a decrease in visual functions, the development of fatigue due to re-adaptation of the eye. Visual fatigue associated with hard work and frequent re-adaptation leads to a decrease in visual and general performance. Each type of activity associated with the need to distinguish one or another object requires a certain level of illumination in the area where this activity is carried out. Generally, the more visually obstructed, the higher the average light level should be. However, excessive local brightness can cause glare. When a bright light source enters the field of view, the eye loses its ability to distinguish objects for a while. Glare can be direct, when it is caused by bright light sources in the field of view, or reflected, when light is reflected from highly reflective surfaces. The human eye is protected from being hit by too bright light by the blinking reflex (approximately 0,16-0,18 s), eye rotation, and head movement when exposed to bright light. For health purposes, the response time is defined as 0,25 s. To create a normal light environment, various lighting systems are used. Distinguish the following types of lighting. Daylight - lighting of premises with light coming from the sky (direct or reflected), penetrating through the light openings in the external enclosing structures. It is subdivided into lateral, upper and combined. The normalized characteristic is the coefficient of natural illumination. Lateral natural lighting - natural lighting of the room through the light openings in the outer walls. Upper natural lighting - natural lighting of the room through the lanterns, light openings in the walls (in places where the height of the building varies). Combined natural lighting - a combination of overhead and side natural lighting. Artificial lighting - lighting of rooms and other places where there is not enough natural light. It is divided into working, emergency, security, duty, general, local and combined. If necessary, part of the working or emergency lighting fixtures is used for emergency lighting. Work lighting provide in all premises, as well as in areas of open spaces intended for work, the passage of people and traffic. For premises with zones with different natural lighting conditions and with different modes of operation, separate control of working lighting is provided. Emergency lighting - lighting of objects for various purposes, which does not stop or is automatically put into action when the working (main) light sources are suddenly turned off. Designed to ensure the evacuation of people or the temporary continuation of work at facilities where a sudden shutdown of lighting creates a risk of injury or unacceptable disruption of the process. It is divided into security lighting and evacuation lighting. Security Lighting - lighting provided for in case of emergency shutdown of working lighting, as a result of which the following are possible: a long-term disruption of the technological process; disruption of the operation of such facilities as power stations, radio and television transmission and communication nodes, control rooms, water supply, sewerage and heating pumping units, ventilation and air conditioning installations in industrial premises where work stoppage is unacceptable, etc. security lighting (in the absence of special technical means of protection) is provided along the borders of territories protected at night. Any light sources can be used, except for cases when the security lighting is automatically turned on only when an alarm or other technical means is triggered. In such cases, incandescent lamps are used. Emergency lighting - lighting during non-working hours. The scope, illumination values, uniformity and quality requirements are not standardized. General lighting - lighting, in which the luminaires are placed in the upper zone of the room evenly (general uniform lighting) or in relation to the location of the equipment (general localized lighting). local lighting - lighting, additional to the general one, created by lamps that concentrate the luminous flux directly at the workplace. Combined lighting - lighting, in which local lighting is added to general lighting. Combined lighting - lighting, in which natural lighting, which is insufficient according to the norms, is supplemented by artificial lighting. Evacuation lighting - lighting for the evacuation of people from the premises in case of emergency shutdown of normal lighting. Such lighting (in premises or in places of work outside buildings) should be provided for:
Sources of artificial lighting are gas discharge lamps and incandescent lamps. Gas-discharge lamps preferred for use in artificial lighting systems. The luminous flux from gas-discharge lamps is close in spectral composition to natural light and therefore more favorable for vision. However, gas-discharge lamps have significant drawbacks, which include the pulsation of the light flux. When considering rapidly moving or rotating parts in a pulsating light flux, a stroboscopic effect occurs, which manifests itself in the distortion of the visual perception of objects (instead of one object, images of several are visible, the direction and speed of movement are distorted). In industrial lighting systems, fluorescent discharge lamps are used, which have the shape of a cylindrical glass tube. The inner surface of the tube is coated with a thin layer of phosphor, which converts the ultraviolet radiation of a gaseous electrical discharge into visible light. Fluorescent discharge lamps, depending on the phosphor used in them, create a different spectral composition of light. There are several types of lamps: daylight (LD), daylight with improved color rendering (LDC), cool white (LHB), warm white (LTB) and white light (LB). In addition to fluorescent discharge lamps (low pressure), industrial lighting is used high pressure discharge lamps:
Incandescent lamps are also used to illuminate industrial premises, in which the glow occurs by heating the filament to high temperatures. They are simple and reliable in operation. Their disadvantages are low luminous efficiency (no more than 20 lm/W), limited service life (up to 1000 hours), predominance of radiation in the yellow-red part of the spectrum, which distorts color perception. Lighting systems use incandescent lamps various types:
Iodine cycle incandescent lamps are becoming more and more common - halide lamps, which have a better spectral composition of light and good economic characteristics. The quality indicators of lighting in industrial premises are largely determined by the correct choice of luminaires, which are a combination of a light source and lighting fixtures. The main purpose of luminaires is to redistribute the luminous flux of light sources in the directions required for lighting, mechanically fasten light sources and supply electricity to them, as well as protect lamps, optical and electrical elements from environmental influences. Authors: Fainburg G.Z., Ovsyankin A.D., Potemkin V.I.
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