[Measuring the calibration factor of a light scattering dust monitor for CO2 arc welding fumes].

In Japan, a light scattering type digital dust monitor is most commonly used for dust concentration measurement in a working environment. In this study, the calibration factors of a digital dust monitor (K-factor) for several welding fumes were measured in a laboratory. During the experiment, fumes were generated from CO2 arc welding performed by an automatic welding robot. The examined welding wires were JIS Z 3312, Z 3313, Z 3315, Z 3317 and Z 3320. The mass and relative concentrations of the welding fumes were measured simultaneously by a total/respirable (TR) dust sampler and a digital dust monitor at a welding current of 100 A, 150 A, 200 A, 250 A and 300 A. The particle size distributions of welding fumes were measured by a low pressure impactor at a welding current of 100 A and 300 A. A significant effect of the welding current on the K-factor was recognized for all the examined wires. In the most remarkable case, a four-fold difference in the K-factors was found when the fumes were generated from a flux cored wire for mild steel (JIS Z 3313). The particle size distributions of fumes were also affected by the welding current. The coefficients of variation in the measured K-factor were 7.8-40.5%.