10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Filtration Performances Study of Porous Media Composing Protective Clothing Against Solid Aerosols
LOÏC WINGERT, Ludovic Tuduri, Yves Cloutier, Stéphane Hallé, Ali Bahloul, Dominique Tessier, Jean-Luc Giraudel, Patricia Dolez, Pearl Yip, IRSST/ETS
Abstract Number: 918 Working Group: Control and Mitigation
Abstract Aerosols found in workplaces depend on workers activity or industrial processes (metallization, asbestos removal or waste treatment …). The particles emitted by these activities can be very different from each other. Metallization fumes are made, for example, of ultrafine particles (UFPs) of metal oxide whereas those found in electronic waste industry are often micron-sized and composed of heavy metals. Some micron-sized particles, such as the beryllium, represent a proven health hazard by skin contact leading to airborne dermatitis. Only a few studies are available on skin damages related to UFPs. Nonetheless, they already highlight a risk of cytotoxicity and migration to ganglia and organs. Despite these potential danger to the skin, no cutaneous threshold limit values (TLV) exists for solid aerosols. This absence of TLV together with the known health hazards of some common solid aerosols and the lack of knowledge on the UFPs has led, as a precaution, to the use of chemical protective garments (CPG). According to the ISO 16602 standards, CPG against solid aerosols are classified as type-5 and must meet a minimal performance level defined by the ISO 13982-1 and ISO 13982-2 standards. Since there is no hierarchy between all the certified type-5 CPG, significant differences between their protective efficiency could exist and this might lead to an over or under-protection of the workers.
Thus, it was decided to study the filtration performances of the fabrics/materials composing a wide range (20) of type-5 CPG among those available in North America. Amongst, the CPG selected for this study nine were made of microporous fabrics (MP), ten of multilayered nonwoven fibrous media (SMS, SMMS/SMMMS)* and one of a fabric produced by flash spinning process (FS). In order to expose these materials to a wide range of particle sizes (ultrafine to micron-sized), such as those that could be found in workplaces, a 20 nm to 2000 nm diameter sodium chloride aerosols was produced by nebulization in a wind tunnel. Furthermore, penetration experiments were performed at three different low air velocities (0.05, 0.15, 0.3 cm/s) in order to be as close as possible to velocities encountered in real situations. To ensure the robustness of the results, each experiment was triplicated. The collection efficiency was computed from the particle size distributions measured upstream and downstream of the tested samples by using a SMPS (3936, TSI) / APS (UVAPS 3314, TSI) tandem. In addition to the penetration or collection efficiency, the air permeability of the different CPG was also measured.
These permeability measurements allowed, for the first time, to rank the materials of the most commonly used type-5 CPG in North America into distinct clusters corresponding to the different kinds of materials (MP, SMS, SMMS/SMMMS, FS), regardless of the manufacturing company. Separated material groups were also observed from the collection efficiency measurements, but with some differences. In particular, the SMS materials showed very different collection efficiency from each other, i.e., between 45% and 99%. These differences were explained by microscopic analysis and by the physical characterizations of the media. Given that air and vapour permeability are factors correlating with thermal comfort, all these results, constitute a first important step for the choice of the most suited CPG against solid aerosols for a given workplace.