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The first step to identifying what lighting solution can be utilized in the cleanroom facility is determining the ISO classification. The higher the ISO classification, the greater the number of particles allowed into the controlled environment. This means there will be fewer air filters taking up space in the ceiling. In the most stringent cases, the entire ceiling must be covered with filters to allow the absolute minimum amount of particles into the environment.
Airflow systems create lighting challenges
Everything in the cleanroom, including the lighting fixtures, is designed to ensure successful air filtration and maintain the laminar airflow in a contamination-free environment. Depending on the function of the controlled environment, a cleanroom will use either HEPA or ULPA filtration. These air-filtering systems are typically an expensive component and one of the first to be considered in construction. They take up a majority of the ceiling space, which leaves a real challenge for lighting the environment.
Hours of thorough research and design are required to create cleanroom lighting fixtures that maintain the integrity of the space and work effectively with the HVAC system. Regardless of the industry, every cleanroom lighting design should be virtually maintenance-free and provide the right amount of illumination.
Common fixture styles
The need for multiple air filters in cleanroom facilities leaves minimal space for light fixtures. There are three common fixture styles for cleanrooms that maximize the use of the space: recessed troffers, surface-mount fixtures, and surface-mount teardrop fixtures. These are best-suited for use in cleanroom facilities, depending on ISO classification.
Recessed troffers: These fixtures are ideal for cleanrooms designated with an ISO 8 to ISO 5 classification because they have enough space in the ceiling and plenum. While rooms with an ISO 8 and ISO 7 classification have more space in the plenum than rooms with a classification of ISO 6 or ISO 5, both environments can use recessed fixtures. Environments with these classifications are typically electronic assembly, pharmaceutical processing, semiconductor manufacturing, and chemical lab facilities.
Surface mounts: For more demanding environments—those with ISO 3 and ISO 4 classifications—surface-mount fixtures can be installed below the ceiling plane. Because of the high air-filtration level required, there typically is not enough plenum space for recessed troffers so surface-mount fixtures are especially efficient.
Surface-mount teardrops: Surface-mount teardrop fixtures are suitable for controlled environments with an open-area design and moderately demanding classifications of ISO 5 and ISO 4. These fixtures are mounted to a 2-in.-wide ceiling grid and are suitable for individual or continuous row mounting. The aerodynamic shape of the teardrop fixture minimizes any disturbance of the laminar airflow.
Achieving effective light quality
In addition to becoming familiar with the fixture styles for each ISO classification, it is important to know what to consider when selecting the exact fixture. Understanding what lighting features are most important for cleanroom environments will help determine the most efficient solution that requires the least amount of maintenance possible.
In most cases, cleanroom facilities produce and/or test small objects. Pharmaceutical and semiconductor industries, for example, typically use cleanrooms to manufacture small pills and computer chips, respectively.
Lighting fixtures must provide a high level of illumination so employees have enough light to carefully handle small components. Illumination levels may vary depending on the different process areas within the cleanroom, so it is important for the specifier to review each process area to determine the illumination level required for each task.
When specifying fixtures, the goal is to select the least number of fixtures that can provide the necessary illumination for a cleanroom. Limiting the number of fixtures helps reduce the amount of maintenance needed. Often, lighting manufacturers can help determine the number of fixtures needed for a given space by reviewing the layout of the cleanroom facility.
Furthermore, surfaces in most cleanrooms tend to be highly reflective. Fixtures need to produce a high intensity of light but should not produce any glare. There are high-efficiency fluorescent luminaires on the market today—ones that produce the amount of light intensity needed with minimal glare.
Fixture housings must be constructed of materials such as aluminum, carbon steel, or stainless steel. These help eliminate the chance of contamination and stand up to rigorous cleaning procedures. The fixture should be welded or sealed shut to prevent the passage of particles into or out of the housing. This minimizes the chance for dust or particle collection on the fixture.
In some cases, fixtures should be wet-listed to accommodate cleanrooms that need to be periodically hosed down.
Lenses should have a smooth outer surface, meaning those with prisms should be inverted so the prisms are on the inside of the fixture. This makes the fixture easy to clean and creates less opportunity for contaminants or dirt to collect. Many lenses and diffusers are available for each ISO classification. Acrylic lenses currently are the most common type because they are the most durable.
For cleanroom environments in the semiconductor industry, lenses can be constructed with radio filters so they do not compromise any electronics in the facility.
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.