Lighting, whether natural or artificial, shall be such as to provide good distribution of light and to avoid glare and objectional shadows and extreme contrasts. In artificial lighting, lamps shall be so installed in regard to their height, location, and spacing and shall be so equipped with reflectors, shades, or other suitable accessories as to accomplish these objects.
Bare light sources, such as exposed lamp filaments, located within the ordinary field of the worker's vision are presumptive evidence of glare. The principal causes of glare are:
the light source may be too bright; that is, it may have too high a candlepower per square inch of area;
the light source may be too powerful for comfort; that is, it may have too great a total candlepower in the direction of the eye;
a given light source may be located at too short a distance from the eye or it may lie too near the center of the field of vision for comfort; that is, within too small an angle from the ordinary line of sight;
the contrast between the light source and its darker surroundings may be too great;
the time of exposure may be too great; that is, the eye may be subjected to the strain caused by a light source of given strength within the field of vision for too long a time.
Glare from natural lighting may frequently be reduced by the use of refracting or diffusing glass in windows and skylights, and by the rearrangement of machines and benches so that operators are not required to face windows.
MS s 182.657
June 11, 2008