Evaluation of Saw Blade Designs on Controlling Dust from Cutting Fiber-cement

Abstract

ABSTRACT Fiber-cement can contain as much as 50% crystalline silica and cutting this material has shown to cause excessive exposures to respirable crystalline silica. We conducted this study to evaluate different saw blades for cutting fiber-cement siding, aiming at identifying blade design features that lead to lower dust release. Through laboratory evaluations of 22 saw blades, the releasing rate of respirable dust, i.e., GAPS, was analyzed and compared with and without engineering control measures. Two on-tool passive control measures were specifically evaluated. First, a dust-collecting box with a capped exhaust port was attached to the circular saw. Second, the dust-collecting box was connected to a passive dust collector, which includes a cyclone dust collector and an air filter. Both control measures help collect a portion of the dust with the aid of the induced airflow from the fast-spinning blade. The GAPS generally increased with the number of teeth and the kerf width of the blades. However, the number of teeth seems to have a reduced effect on GAPS for the conditions with the two control measures, possibly due to a higher airflow rate induced by more blade teeth, which results in more dust captured by the dust collectors. The 4-tooth Hitachi blade had the lowest GAPS under all three testing conditions, likely due to fewer teeth, thinner kerf, and its specific design characteristics of a “smooth” gullet optimizing induced airflow and dust transporting into the dust collectors. The control measure with the added passive dust collector provided a dust collection efficiency as high as 66%. The gullet design of the blade seems to play an important role in affecting the amount of dust releasing as well as the collection efficiency of the passive dust controls.