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Tablets & Capsules May 2020 25 high-efficiency particulate air (HEPA) filtration, push- push filters, and clean-in-place (CIP) designs. A push-push filter consists of a working filter and a standby filter. The working filter is inserted first and then pushed down into place by the standby filter, which rests on top of the working filter during operation. When the working filter needs to be replaced, a new standby filter is inserted on top of the existing standby filter, which pushes the old working filter out into a contained bag for disposal. The original standby filter then becomes the new working fil- ter. OEB 4 and 5 materials may also require operators to wear full respiratory suits and other protective equipment. International and US guidelines and regulations also provide direction on containment. The European Union's Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulation established a chemical guideline for the EU that addresses the classification of hazardous and harmful substances. Chemical manufactur- ers and processing plant operators are obligated to dis- close information about how hazardous or harmful a substance is and how users should handle the substance in order to protect themselves. In the US, there's still no single standard that applies to powder transfer safety; however, there are the National Institute for Occupa- tional Safety and Health (NIOSH) guidelines for con- tainment standards; National Fire Protection Association standards 654, 652, and 70, which also cover explosion risks; and MSDSs that define hazards. high. Today, depending on the application, production is either integrated into an isolator or executed within a sealed and closed process to ensure the required dust-free and safe work environment. Such processes increasingly rely on pneumatic vacuum conveying systems to contain the highly potent powders during transfer. Containment requirements for highly potent materials The containment requirements for highly potent materials are always material specific and must therefore be redefined for every material. Acceptable emission lev- els are defined in a powder's material safety data sheet (MSDS). The terms occupational exposure limit (OEL) and occupational exposure band (OEB) are generally used to define the maximum permissible emission levels in a work environment. A material's specific OEL value along with characteristics such as granule size and fluidity play a significant role in determining the design of a process unit handling the material. Not every containment sys- tem is suitable for every material. Throughout the world, there is a standard OEB chart, shown in Figure 1, with the corresponding OELs and the required system type for handling materials in each band. OEBs 4 and 5 (the dark orange and red bands, respec- tively) are the strictest containment levels typical for potent pharmaceutical or hazardous chemical applica- tions. OEB 4 and 5 materials generally must be handled in highly sophisticated, custom-built isolators that use Figure 1 Occupational exposure limit (OEL) and containment system requirement for handling toxic materials in each occupational exposure band (OEB) 5 <1 µg/m3 1 to 10 µg/m3 10 to 100 µg/m3 100 to 1,000 µg/m3 1,000 to 5,000 µg/m3 extremely toxic very toxic toxic mildly toxic non-toxic 4 3 2 1 OEB Toxicity level Isolators Closed systems with double-flap valves Open systems with dual extraction Open systems OEL