As a result of recent research on the potentially adverse health effects of sub-micrometer aerosols, a generation chamber and sampling system was designed to characterize aerosols from a popular welding system that utilized either gas metal are welding or flux cored are welding techniques. The experimental apparatus allowed flexibility in changing are welding parameters, sample locations, and was designed to promote the steady-state generation of fumes over several minutes. In contrast to prior studies where the particle size distribution was weighted by mass without regard to its time/temperature history, the wedding aerosols in this study were temporally collected and weighted by a lower moment, particle number. The results demonstrated that the welding alloy had a marked effect on the particle size distribution, morphology and chemical aspects of the resultant fume. In addition, the particle size distributions from these processes were multi-modal and dynamically changed with time.