Nanotechnology is a rapidly expanding technology in which existing and novel materials are engineered at the nanoscale, typically in the range of 1 to 100 nanometres. Engineered nanomaterials include uniquely manufactured products with unique shapes and enhanced physical and chemical properties, compared with conventional materials of the same composition. There is currently little available information on the explosion risks of these materials. The Health and Safety Executive therefore commissioned this project to investigate the potential fire and explosion hazards associated with nanopowders. Test equipment and procedures were developed to assess the key properties of a selected number of nanopowders. A specialised 2 litre test vessel was developed to determine the explosion characteristics and modified standard test apparatus was used to measure the minimum ignition energy of nanopowders. Resistivity and electrostatic charging characteristics were assessed using specially designed test apparatus. Key information including KSt, Pmax and MIE values were obtained for a range of metal and carbon nanopowders. Generally, the explosibility (maximum explosion pressure, rates of pressure rise and equivalent KSt) of nanopowders were found to be broadly similar to conventional micron-scale powders. However, the minimum ignition energies of some nanopowders were found to be lower than the equivalent material at micron-scale. It was demonstrated that with increasing relative humidity the resistivity of most nanopowders decreases. There was also a tendency for nanopowders to have higher resistivity values than conventional micron-scale powders. All the powders produced electrostatic charge. Generally, the charge developed by nanopowders was comparable with the micron-scale powders.
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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