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Occupational safety course.doc
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2.5.5. Artificial illumination

Artificial illumination is applied in all areas where natural illumination is insufficient and also to illuminate the area when it’s dark.

There is general, focal and combined lighting. Arranging only focal lighting in occupational areas is not recommended at all.

The most familiar type of artificial light is the incandescent lamp in which the radiant source is a hot filament of tungsten. The incandescent filament in a typical 100W bulb has a temperature of only about 2850 degrees K, so its radiation is strongly shifted to the red end of the spectrum. Indeed, about 90% of the total emission of an incandescent lamp lie in the infrared.

Incandescent lamps are cheap, easy to manufacture, convenient to use, they have wide diapason of voltage and power. The main disadvantages are high brightness (may be blinding), not uniform luminous flux, low luminous efficiency (7..20 lm/W), low durability (2,500 hrs).

Unlike incandescent lamps and the sun, fluorescent lamps generate light by a non-thermal mechanism. Within the glass tube of a fluorescent lamp, a mercury vapor arc generates ultra-violet photons. The inner surface of the tube is coated with phosphors, luminescent compounds that emit visible radiation of characteristic colors when they are bombarded with ultra-violet photons. The standard 'cool white' fluorescent lamp has been designed to achieve maximum brightness for a given energy consumption.

Fluorescent lamps advantages are high luminous efficiency (40..100 lm/W); durability makes about 14,000. Disadvantages are luminous flux pulsing what can result in stroboscopic effect, complicated design and structure, necessity to use special startup units, cause initial voltage to turn them on is higher than it’s in power line, and starting time is quite long, throttle noise, expensive.

Fluorescent lamps are manufactured as luminescent, mercury and xenon lamps. Xenon lamps are prohibited to use in occupational areas. Luminescent (low-pressure) lamps are the most frequently used. Fluorescent high-pressure lamps are recommended for high luminous efficiency, stability to external factors and compact design.

Since fluorescent lamps are the most widely used source of light in factories, offices and other workplaces manufacturers produce lamps correspondent to their implement. There are day light fluorescent lamps (LD), day light with advanced color render lamps (LDC), cool white lamps (LHB), warm white lamps (LTB).

Lamps are used in one assembly with luminaries.

Luminarier is the assembly of lamp and lighting armature. Lighting armature focus luminous flux in the space or transfers its properties so as to protect eyes of workers from blinding effect and it also protects lamp from fire, explosion or chemically active environment, mechanical damage, dust, atmospheric factors.

Luminaries are classified by:

  • purpose – for general and focal lighting;

  • design – opened, covered, water-proof, dust-ignition-proof;

  • luminous flux focusing – accent lighting, diffuse lighting, reflected lighting.

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