Industry Recognized Lighting Methods
According to the Illuminating Engineering Society of North America (IESNA), there are three lighting techniques used in industrial spaces: general, localized general, and supplementary. General lighting provides substantially uniform illumination throughout the area. Localized general lighting is required when certain tasks require higher lighting levels than the general lighting scheme. In these areas, increasing the number of luminaires, the number of lamps per luminaire or using higher wattage lamps can be implemented to increase the lighting level. If many of these demanding tasks are in close proximity, it may be more energy efficient to raise the general lighting levels than to have several localized general systems. Supplemental lighting is required for difficult seeing tasks such as viewing very small objects, auditing color samples or performing very difficult inspections. Supplemental luminaires can permit special aiming or positioning of light sources.

Illuminance levels Illuminance is defined as the amount of light (called lumens) reaching a surface and is measured in "footcandles" or lumens per square foot. The metric equivalent is measured in "lux" or lumens per square meter. The appropriate illuminance for a space depends upon how the space is being used in addition to the age of the workers (older eyes require more light), the speed and accuracy requirements of the task, the task contrast, and whether errors affect health and safety.

If there is more than one task for the same area and they require different illuminance levels, the designer can provide for dimming or switching or provide controllable task lighting. The designer can also develop a time-and-importance weighted average illuminance level for the space that would take into consideration the importance of the various tasks and how much time is spent on one task versus another.

Recommended lighting levels are from IESNA Lighting Handbook 9th edition, 2000. Many factors have an impact on proper light levels, including age, speed, accuracy, contrast, glare, flicker, distribution and others.  The influence of these factors may raise or lower the levels shown in the table.  For detailed information regarding these and other related issues, consult the IESNA Handbook.

1. The task may be horizontal, inclined or vertical
2. Minimum level

Lighting Calculations
When performing industrial lighting calculations, many factors can cause the actual illuminance to vary from the calculated illuminance; for example, incorrect surface reflectances, not accounting for large machinery and other obstructions that block light, and inaccurate light loss factors (LLF). Total LLF takes into account that the fixtures will get dirty over time, that lamps will age causing the lumen output to decrease and that ballast operation plays a factor in lumen output. It is always best for the designer to calculate the appropriate LLF and to know the exact reflectances in order to get more accurate illuminance levels; however, the following rules of thumb can be applied for quick calculations.

*Includes ballast factor. Based on energy saving lamps/energy saving ballast or T8 lamps/electronic ballast

Thermal Considerations:

Ambient Temperature Conversion Chart:

Thermal Characteristics of a Fluorescent Lamp:

Fluorescent sources are sensitive to temperature extremes. Optimum light output for most fluorescent lamps occurs when the bulb wall temperature is 100° F.  Any temperature above or below optimum reduces light output.

Fluorescent Ballast Performance:

HID Ballast Performance:

Temperature has a tremendous effect on the life expectancy of a ballast and its related components.  Therefore, it is important not to exceed the maximum ambient rating of the fixture. Operating a fixture in environments that are cooler than its rated ambient temperature will greatly increase ballast life. It is generally accepted that for every 13° C drop below the fixture's  rated ambient temperature, the life of the ballast doubles.  Capacitor life is doubled when ambient temperatures drop 10° C below rating.