| Prior welding research has primarily focused upon characterizing aerosols based upon the mass of the aerosol (e.g., fume formation rates). This is reasonable in that current standards for welding fumes are also mass-based. However, recent research has suggested that sub-micrometer aerosols may have adverse health effects due to their size. As a result, a mass-based characterization may not be adequate if the toxicologically significant parameter is a lower moment of the particle size distribution such as the particle number or particle surface area. Additionally, prior research has focused upon collecting and characterizing the welding process aerosol without regard to the time-temperature history of the aerosol. Temporal characterization is necessary because factors such as the deposition efficiency in the lungs, potential toxicity, removal efficiency by an engineering control device relate directly to the size and chemical aspects of an aerosol.;To attempt to address these shortcomings, a generation chamber and sampling system was designed to characterize aerosols from a popular welding system that utilized either Gas Metal Arc Welding (GMAW) or Flux Cored Arc Welding techniques. The experimental apparatus allowed flexibility in changing arc welding parameters, sample locations, and was designed to promote the steady-state generation of fumes over several minutes.;To further characterize the welding fumes from a GMAW process, several welding parameters such as droplet mass transfer mode, shield gas composition, and welding spatter was studied to determine their effect on the resultant aerosols.;Finally, research was conducted to determine the efficacy of a commercially available air-cleaning device in removing aerosols from a gas metal arc welding process. The system evaluated was self-contained such that the filtration system and exhaust fan were found within the same unit. Filtration was accomplished through the use of a pleated pre-filter followed by an extended-media filter with varying rated removal efficiencies. Several extended-media filters were evaluated with rated efficiencies of 40%, 65%, 95%. The air-cleaning unit was also retrofitted with a HEPA box filter, rather than the "HEPA like" box filter provided by the manufacturer, to determine its performance in removing welding fumes from the gas-stream. (Abstract shortened by UMI.)... |
