From:Gary Jones(firstname.lastname@example.org )
Date: Lighting Levels
FYI - From Lab Safety's Saf-T-News at http://www.lss.com/refinfo/saftnews/
When you need light, what do you do? Just find the switch and flip it, right? For many of us, that's as much thought as we give to lighting. But getting the best quality light in the right intensity is a little more complicated. Sorting out the complexities of artificial lighting options starts with understanding the differences between bulb types. All light bulbs are not created equal. The type you choose can make a big difference in the quality of light, its suitability to the task at hand, and what affect it can have on your eyes. Here is a list of some common bulb types along with advantages and disadvantages.
INCANDESCENT Still the most commonly used bulbs in households, incandescents create a very natural light. They cost less but use more energy and have a shorter life than fluorescents.
HALOGEN Halogen light is extremely bright, so halogen bulbs are well suited for lighting large areas. Because halogen bulbs can also become extremely hot, they should be considered potential fire hazards and used with appropriate care.
FLUORESCENT The most obvious advantage of fluorescents is their cost efficiency. They can last from ten to twenty times longer than incandescents while using only a third to a fifth of the electricity to achieve the same brightness. The initial cost is considerably higher than incandescents, but fluorescents offer substantial savings over the life of the bulb. Recent improvements in the design of compact fluorescent bulbs have made it easier than ever to use them to replace incandescents.
HIGH INTENSITY DISCHARGE (HID) HID bulbs generate light by passing current through gasses. The powerful light that results is commonly used outdoors in floodlights or to light parking lots. If there is a disadvantage to HID bulbs, it is a slow warm up time, up to several minutes before reaching full brightness.
Just as important as choosing the appropriate bulb is determining the difference between how much light is present and how much light should be present. The tool for this task is a light meter. Light meters actually measure how much light is being given off in a particular area. Light levels can be measured in lux, lumens, candlepower or footcandles.
The following chart uses footcandles to describe appropriate light levels for different situations.
|Lighting Situation||Light Level in Footcandles|
|Open parking area (High/Medium Activity)||2/1|
|Covered parking area||5|
|Corridors and lobbies||10-20|
|Tasks requiring reading of large print, typed originals, ink handwriting||20-50|
|Tasks requiring reading of small print, poor copies, pencil handwriting||50-100|
|Tasks requiring reading of very poor copies or pencil handwriting||100-200|
For general information see EZ Facts® document No. 128, Industrial Lighting
Go to: http://www.labsafety.com/refinfo/ezfacts/ezf128.htm.
For more on light levels, see EZ Facts® document No. 267, Comparative Noise & Light Levels. Go to:
For more on emergency light fixtures, see EZ Facts® document No. 265, Exit and Emergency Lighting. Go to: