Evaluation of an aerosol photometer for monitoring welding fume levels in a shipyard.

A direct reading aerosol photometer (Sibata P-5 Digital Dust Indicator) was used to assess fume levels from welding and burning operations in a shipyard. The photometer was calibrated with gravimetric analysis of filter samples collected simultaneously with instrument readings. A six-fold difference between calibration factors for personal and area samples was found. This difference can be explained by expected changes in particle size distributions in welding fume. Monitoring of various work situations was performed in order to assess the value of the photometer for the measurement of fume. Measurements categorized by enclosure of space and quality of ventilation indicated the presence of high fume levels in semi-enclosed and enclosed spaces. The build up of welding fume in an enclosed space occurred over several minutes after the arc was struck. Decay likewise required several minutes. During welding, wide fluctuations of fume concentrations were found. Thus a single reading was not adequate to characterize average fume levels. Although this type of instrument is useful for locating areas with high fume levels and monitoring the effectiveness of ventilation, the uncertainty in calibration factors makes accurate determinations of fume levels difficult.