Foot candle (fc) requirements vary throughout cleanroom facilities, from 30 fc in mechanical/electrical rooms to 100 fc or more in the cleanroom. Some cleanroom applications that involve food inspection and grading require at least 150 foot-candles. The engineer should work with the cleanroom staff to determine the proper foot-candle requirements in each of the areas within the space.
Revision B of Federal Standard 209 (now 209E) originally contained a requirement for 100 fc in main cleanroom areas. In practice, 100 fc has been viewed as excessive and detrimental to eye comfort levels in most cleanroom applications. In addition, it can be difficult to obtain 100 fc in ISO Class 4 (Class 10) and lower cleanrooms, since most of the ceiling space is dedicated for air filters. Attempts to obtain 100 fc would reduce the available cleanroom ceiling space for filters and reduce overall energy efficiency. Surveys of existing cleanrooms have revealed adequate lighting levels in the 60 to 80 fc range. These illumination levels appear to accommodate user comfort and most types of cleanroom processes.
Advancements in cleanroom lighting
Continuous technological innovations have made the cleanroom industry dynamic and ever-changing. Manufacturing has become more demanding and regulations are becoming more stringent. Given those factors, plus the current focus on energy savings and the environment, a growing number of cleanroom lighting projects today are retrofits or renovations.
Currently, fluorescent lighting is the most common source for lighting cleanrooms. However, because of the need for more energy-efficient and reduced-maintenance options for cleanroom facilities, research and advancements in LED luminaires for cleanrooms are on the horizon.
Even with international standards for cleanroom facilities, it is important for the lighting specifier to consider the function of the specific controlled environment. Ultimately, the primary goal for all cleanroom facilities is to ensure there is no contamination and the space is properly illuminated for the task at hand. Selecting the most reliable and efficient lighting fixtures can help ensure both of these objectives are achieved.
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