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36 Pharmaceutical Technology BIOLOGICS AND STERILE DRUG MANUFACTURING 2020 P h a r mTe c h . c o m on regular BSC testing and certification follow- ing purchase and installation in order to respond to gradual filter loading. With earlier models, the gradual build-up of contaminants captured in the filter would result in a subsequent reduction in air velocity, compromising the BSC's ability to capture contaminants. Design efforts have been directed at overcoming this threat to precise airf low and im- proving monitoring systems. Modern BSC design features include: • Fan and filter systems that automatically ad- just fan speed to compensate for filter loading • Improved filter design, reducing the inci- dence of leaks found in certification tests • Airf low alerts that signify to the operator if air velocity moves above set thresholds • Screens that clearly communicate whether a window needs to be repositioned or if the air barrier is keeping room contaminants out. When selecting a BSC, it is important to con- sider the specific processes and applications in the laboratory in which the cabinet will be used. For example, some laboratories require additional con- nections for the BSC interior, such as power and data, or piped-in media such as combustible gas. As cramped conditions compromise processes and contamination protection, laboratories with exten- sive equipment assets would benefit from larger BSCs. While the most common width of a BSC is approximately four feet, other sizes can accom- modate smaller spaces, more equipment, or envi- ronments in which two people work concurrently in one space. In addition to performance criteria and moni- toring features, safety is another important com- ponent to consider. Laboratories working with volatile chemicals or gases may require the instal- lation of a canopy/thimble connection to the top of their BSC, to allow exhaust to be directed to a designated channel. Specialized BSCs are available for those who must contain dangerous substances, such as those preparing hazardous drugs. Infrastructure requirements To ensure optimal airf low, filters and other sys- tems must be validated and shown to function as vendors claim they do. BSC testing and certifica- tion must be performed at the prototype stage in a recognized validation laboratory and then again at the manufacturing factory where the cabinet will be used. This practice increases the likelihood that the BSC will remain effective in preventing cell-culture contamination, because it will permit any design or manufacturing issues to be f lagged early. Once the BSC is installed in a laboratory, testing and certification will be imple- mented by specially trained inspectors whose ex- perience and skills are regularly assessed, before use and then at least annually thereafter. Prototypes of each BSC design are assessed ac- cording to NSF/ANSI 49 (National Science Foun- dation/American National Standards Institute 49) (1), an internationally recognized standard that assesses quality, compliance, and safety. Assess- ment examines a wide range of parameters, includ- ing equipment design, construction, performance, product and environmental protection, reliability, durability, cleanability, noise level and illumination control, vibration control, and electrical safety (2). Once the individual BSC arrives in the laboratory, it must be certified on site and periodically thereafter to ensure it is operating as required and that it func- tions well within that specific laboratory. Although a thorough assessment process can help assure Operations