Abstract
To investigate the effects of circular sawing conditions and moisture content of workpieces on the mass concentration of airborne dust generated from circular sawing of sugi (Cryptomeria japonica), the mass concentration of airborne dust of diameter 7.07 µm or less during sawing was measured at a worker's breathing zone with a light-scattering type dust monitor at intervals of one second. The sawing parameters varied in this experiment were workpiece feed speed, circular saw revolution speed, and the feed per tooth. The geometric mean of mass concentration was more affected by the circular saw revolution speed than by specimen feed speed and feed per tooth, and increased with the circular saw revolution speed. This implies that the quantity of airborne dust that reached a worker's breathing zone increases with increasing peripheral circular saw speed. Although the geometric means for dust collector operation were lower than the occupational exposure limit (OEL), individual measurement values of mass concentration during sawing were sometimes larger than the OEL. The probability that the measurement value was larger than the OEL was 0.0 for 1500 rpm of circular saw revolution speed, and 0.03-0.18 for 2000 and 2500 rpm. The geometric standard deviation of mass concentration was not affected by the sawing conditions. There was a negative relationship between the geometric mean of mass concentration and workpiece moisture content, and a positive relationship between the geometric standard deviation of mass concentration and workpiece moisture content.
