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

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., G_APS, 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 G_APS 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 G_APS 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 G_APS 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.