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首页> 美国政府科技报告 >In-Depth Study Report: Control Technology for Crystalline Silica Exposures in Construction: The Effect of Exhaust Flow Rate Upon the Respirable Dust Emissions for Tuck Pointing Operations and a Preliminary Evaluation of a Ventilated Tool for Brick Cutting at International Masonry Institute, Cascade, Maryland.
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In-Depth Study Report: Control Technology for Crystalline Silica Exposures in Construction: The Effect of Exhaust Flow Rate Upon the Respirable Dust Emissions for Tuck Pointing Operations and a Preliminary Evaluation of a Ventilated Tool for Brick Cutting at International Masonry Institute, Cascade, Maryland.

机译：深入研究报告：结构二氧化硅暴露在施工中的控制技术：排气流量对塔克指向操作的可吸入粉尘排放的影响以及马里兰州卡斯卡德国际砌体研究所用于砖切割的通风工具的初步评估。

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As brick buildings age, mortar deteriorates and needs to be replaced. Before replacing the mortar, the existing mortar is removed to a depth of 0.5 and .75 inches. Typically, a 4-inch diameter grinder, operated at 10,000-12,000 rpm, is used to remove mortar. Mortar removal causes exposures to respirable crystalling silica concentrations as high as 10 gm/cu(m). A tool resembling a router can also be used to remove mortar. For four different shrouds, the effect of exhaust flow rate upon respirable dust emissions was experimentally evaluated. To conduct this testing, a small brick wall was built and enclosed in a hall-shaped, ventilated test chamber. The grinder was mounted on a mechanical trolley which moved the grinder horizontally down the wall at a constant velocity of approximately 1 m/min and the mortar was removed at a fixed cut depth of 0.5 or 0.75 inches. A vacuum cleaner equipped with high efficiency filters (99.9% at 0.3 cubic(m)) exhausted air from the shrouds to a location outside the enclosure. The vacuum cleaner's exhaust air flow was varied by controlling the voltage applied to the vacuum cleaner. An air flow rate of 2794 cubic feet per minute was drawn through the test chamber and past mixing baffles and into an exhaust duct. A time-of-flight aerosol spectrometer was used to measure the respirable dust concentration in the duct.

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