Figure 13. Air curtain safety cabinet hood that uses push-pull ventilation (Used with permission from Huang et al. [2007a].)
3.4.2.5 Summary
Overall, the published studies suggest that the selection of a fume hood with improved operating characteristics such as a VAV hood provides better operator protection than conventional fume hoods when handling dry nanomaterials. When using any hood, the worker should strive to maintain the face velocity in the recommended range of 80–120 ft/ min [ACGIH 2013]. Additionally, proper use of the engineering control by the operator and validation of the performance of the control equipment are essential for risk mitigation. Newer nano hoods based on pharmaceutical weigh-out enclosures may be a reasonable alternative to larger fume hoods when only small-scale, benchtop manipulation of powders is needed. These hoods have proven effective in the pharmaceutical industry but need more thorough evaluation to assess the impact of lower airflow rates on containment performance, especially in the industrial environment. BSC-type hoods are commonly used for containing hazardous powders in hospitals for hazardous drug formulation and may have features designed to improve containment performance over traditional fume hoods. However, there are few published studies on their effectiveness for containing nanomaterials. The selection of a BSC appropriate for use with nanomaterials is essential. Considerations including how to clean the cabinet after use, how to maintain the BSC during required maintenance such as filter change-outs, and proper exhaust configuration (sending exhaust out of the production area versus recirculating exhaust air) should be considered prior to use. Glove box isolators typically provide a greater level of worker protection but at a cost of reduced access and limited operational scale. Newer hood designs, such as the air curtain fume hood, have shown excellent containment performance in initial studies and may be potential control options in the future.
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Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes
