Fumes are formed from i) the base and filler metals, ii) the electrode coating or the shielding gas, iii) coatings or contaminants on the base metal (if present), and iv) the reactions that occur during the welding process [Battelle-Columbus Laboratories, 1973]. According to Stern [1979] as much as 95 percent of the welding fumes in SMAW originate from the electrode. Although the arc welding process is complicated, it is expected that the particle size distribution, fume generation rate, and the fume composition produced during the operation may differ significantly with different welding variables, including the electrode type and diameter, welding current, welding speed, welding angle, and current type (AC or DC).