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In-Depth Survey Report: Concrete Surface Preparation Tools Machine 5
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2016/01/01
[PDF-1.13 MB]
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Description:Workplace exposure to respirable crystalline silica can cause silicosis, a progressive lung disease marked by scarring and thickening of the lung tissue. Quartz is the most common form of crystalline silica. Crystalline silica is found in several construction materials, such as brick, block, mortar and concrete. Construction tasks that cut, break, grind, abrade, or drill those materials have been associated with overexposure to dust containing respirable crystalline silica. Colored, stained, and polished concrete floors are increasingly popular for use in homes, offices, retail establishments, schools, and other commercial and industrial settings. Some businesses specify integrally-colored concrete floors in new stores in place of vinyl composite tile. Polished concrete floors are durable, sanitary, and easy to maintain. NIOSH scientists are conducting a study to develop and evaluate engineering control recommendations for respirable crystalline silica from concrete polishing operations. This survey was part of that study. NIOSH staff visited the GMI Engineered Products, LLC (GMI) facility in Bluffton, Ohio on August 28, 2014. During the site visit, personal breathing zone (PBZ) air samples were collected to measure the respirable dust and respirable crystalline silica exposures of the operator while he used a concrete polisher (G-320D, Concrete Polishing Solutions, Norris, Tennessee). Additionally, area samples were collected on top of the machine during the completion of the task. The G-320D floor polisher was outfitted with a local exhaust ventilation system consisting of two exhaust ports located on the back of the shroud that encased nine polishing tools. The exhaust from both ports was connected to a vacuum system rated at approximately 10987 liters per minute (L/min) (388 cubic feet per minute (cfm)) of suction. The vacuum was equipped with a pre-separator. Once through the pre-separator, the air stream passed through a High Efficiency Particulate Air (HEPA) filter and then recirculated to the room. The aim of this survey was to collect emissions data from the concrete polisher using different grits while operating the dust collection system provided with the machine. Sample times varied based on the length of time needed to polish a rectangular area of 15.8 square-meters (m2) (170 square-feet (ft2)) with a given grit and ranged from 31 to 34 minutes with an average sample time of 32 minutes. A bulk sample was collected from the dust captured in the bag filter of the vacuum system connected to the concrete polisher; it contained 21% quartz. No cristobalite or tridymite were detected in the bulk sample. Therefore, for the purposes of this report the terms respirable crystalline silica or respirable quartz may be used interchangeably. If exposures were to continue as measured throughout the entire workday and assuming constant dust generation rates, PBZ quartz concentrations with the local exhaust ventilation operating would range in concentrations between the limit of detection (LOD) and 19.174 micrograms per cubic meter (microg/m3). All the recorded concentrations are below the NIOSH Recommended Exposure Limit (REL) for respirable quartz of 50 microg/m3 as a time weighted average for the grits evaluated during this visit. The G-320D concrete polisher evaluated in this survey was equipped with a Bull 1250 Dust Collection System (SASE Company, Kent, Washington) intended to control and remove dust particles generated during the concrete polishing process. The dust control system adequately controlled worker exposure to respirable crystalline silica during this site visit. Additional evaluation is recommended to collect repeated samples using the same equipment to quantify the actual air flow of the vacuum system and establish a correlation between the actual and the listed airflow.
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DOI:10.26616/NIOSHEPHB36814a
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Pages in Document:1-24
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NIOSHTIC Number:20047542
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NTIS Accession Number:PB2016-102603
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Citation:Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB 368-14a, 2016 Jan; :1-24
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Federal Fiscal Year:2016
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Peer Reviewed:False
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Resource Number:EPHB-368-14a
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