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Understanding Foot Candles vs. Lumens for Temporary Job-Site Lighting

Mine work underground.jpgTypically, we are conditioned to pick out bulbs for lighting based on wattage, however that is not the best way to choose lighting when utilizing LED’s for temporary job site lighting. It is important to understand wattage measures “how much electricity” will be used, and not the amount of light. LED technology requires much less energy to produce the same amount of light that a past incandescent bulb would have.

The Federal agency for Occupational Safety and Health Administration (OSHA) has regulation standards for minimum illumination intensities required for certain areas of operation. Hence the importance in understanding foot candles & lumens.

So what is a Foot-Candle?

  • A foot-candle is defined as the illuminance on a one square foot surface from a uniform source of light. The key is to remember that foot-candles are a unit of measure for how much light is received at a location. In other words a foot-candle is a unit of measure for quantifying the certain intensity of light falling on a given object or in laments terms, the amount of light thrown from a fixture.

What are Lumens?

  • A lumen is a measure of the total quantity of visible light emitted by a source. Lumens are a great measurement for comparing different types or kinds of light sources as it focuses solely on the lights output. 

This brings us to understanding foot-candles and their importance in the lighting industry. Foot Candles are a common unit of measurement for calculating adequate lighting levels of job sites common in construction or confined space job sites. For example, consider your office. An open office space commonly has a 40 foot-candle recommendation. While a commercial warehouse on the other hand commonly has a 20 foot-candle recommendation.

Foot-candles and lumens are both units of photometry and used to quantify illuminance that is detectable to the human eye. It is important to note they measure different aspects of light. Always remember, Foot-candles measure the amount of light on a surface. While lumens measure the amount of light emitted from a source. It is important to know the meaning of both since there can be significant loss of light as it travels to a surface, due to distance, direction and many other factors.

It really isn’t a complex equation, you just need to make sure you are speaking the same language with your engineering team when trying to spec out temporary job site lighting. The advantages of today’s technology help evaluate dimensional spaces with the need for lumen efficacy or foot-candle footage. Having the proper illuminance can save you time and money on your next job site, and make sure that your partner has an engineer on staff that has experience in photometric analyses too!


Written by: Josh Ericson

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