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| Module 1: Occupational Hygiene - Section 5: Instrumentation |
| OH5.14: Principles of Illumination - Legislative Requirements and Lighting Surveys |
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| Module 1: Occupational Hygiene - Section 5: Instrumentation |
| OH5.14: Principles of Illumination - Legislative Requirements and Lighting Surveys |
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Section of 8 of the Occupational Health and Safety Act requires employers to provide a work environment that is safe and without risk to the health of his employees. 4 Section 3 of the Environmental Regulations stipulates that every workplace should have suitable and sufficient lighting. 5 In addition, suitable and sufficient emergency lighting should be provided and maintained for workers who are likely to be in danger in case of failure of artificial lighting. The regulations contain a list of illumination levels that should be maintained for various industries and types of tasks performed.
Although there are prescribed lighting levels, the amount of lighting needed varies and depends on type of task, type of surface, general work area and individual's vision. Therefore, the schedule of lighting levels should be treated as guidelines.
In order to fully understand the distribution of light in a room and to determine whether workplace illumination levels are suitable and sufficient for the work to be undertaken, two stages of assessment are required. 6 The first stage is to complete a subjective examination of general illumination and the second stage is quantitative evaluation of lighting levels.
Subjective evaluation of lighting entails recording information about the nature of the workplace, and a description of the general lighting systems. A description of the workplace covers dimensions of production or office areas, condition of floor and wall surfaces, colours of walls and ceilings. A description of the general lighting conditions include the quantity of light sources, condition of luminaires (sources of lighting), types of lamps, wattage outputs, spacing, mounting as well as answering questions about light servicing procedures.
Identify the areas where work is performed, the activities of workers there, the presence of glare and rotating machines.
Lighting levels are measured at various task locations for task lighting or at various locations throughout the workplace for general lighting. SABS Code of Practice 0114 of 1973 specifies the type of instruments that are to be used, and outlines the procedure to be followed when evaluating illumination levels in the interior of buildings. 7
Since most illumination measurements and recommendations for lighting levels are given in units of illuminance, called lux (lx), it is desirable to have a device that measures Lux directly. A Lux (or light) meter is generally used to measure lighting levels. The light meter is a photoelectric device that causes an electric current to flow in the measuring circuit and this current is registered on a suitably calibrated meter.
The ideal instrument for workplace measurements should have a range of 0 - 2500 Lux and should have the photocell separate from the display unit but connected by a length of cable. This arrangement allows the meter to be read without the observer overshadowing the cell.
It is important to use a photocell which incorporates a colour-correcting filter and is cosine corrected. Colour-correcting means the sensitivity to light of the different wavelengths is matched to the sensitivity of the human eye (rather like the sound measuring devices are matched to the human ear. Cosine corrected means that the photocell responds accurately to light arriving on the cell at all possible levels of illumination.
To measure illumination levels, the photocell is placed at the point where the visual task is performed. To measure illumination over a wide area, the usual procedure is to divide up the area into imaginary squares and to take measurements at the center of the square. The average illumination is then compared with the illumination standards contained in the schedule in the regulations.
