Figure 18. A unidirectional downflow booth for handling larger quantities of powders (Used with permission from Esco Technologies, Inc. [2012].)
3.4.3.3 Large-scale Material Handling/Packaging
Unidirectional flow booths, or downflow booths, as seen in Figure 18, are used in pharmaceutical applications for large-scale powder packing, process loading, and tray dryer loading [Hirst et al. 2002]. Similar applications have been proposed for handling hazardous dye powders. In general, these booths supply air from overhead (commonly at 100 fpm) over the full depth of the booth. Particles generated by processes carried out in the booths are captured and carried to the exhaust registers, which are located along the back wall of the booth. For the nanotechnology industry, these booths may provide a flexible solution for several common processes, including packaging of materials, transferring materials between process containers, or loading materials into containers for post processing.
Floura and Kremer [2008] evaluated a downflow booth used for transferring 25 kg of lactose (a surrogate pharmaceutical material) from drum to drum inside a downdraft booth. Air samples were collected in the operator’s breathing zone and around the perimeter of the process during the transfer operation. The operator scooped the lactose powder from the initial drum into the final product drum until it was nearly empty and then carefully inverted the bag to pour the remainder of the contents into the final container. With no active ventilation controls, the concentration within the operator breathing zone averaged 2,250 µg/m3. When the ventilation inside the booth was turned on, the breathing zone concentration was substantially reduced to an average of 1.01 µg/m3. Finally, the authors
Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes
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