Health hazard evaluation report: HETA-2008-0045-3145, unknown gases generated from a silicon wafer grinding filtration process - Colorado.
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, HETA 2008-0045-3145, 2011 Nov; :1-25
NIOSH received a request from an employer representative for an HHE at a semiconductor manufacturing plant in Colorado. The request concerned unknown gases that were pressurizing and heating a covered 55-gallon metal storage drum ("drum") containing used filters from a silicon wafer grinding filtration process. The requestor was concerned that disposing of these used filters in covered drums may present a safety and health hazard to maintenance employees working in the filtration process area. No health effects among maintenance employees were listed in the request. We visited the plant in February 2008 and March 2009. We collected PBZ, GA, and task-based air samples for H2, CO, and CO2. We analyzed the samples with different sampling and analytical measurement techniques. We spoke with maintenance employees about their symptoms and reviewed the company's previous air sampling reports. We found that H2 was being generated inside the covered drums and that the concentrations increased with time. We also measured CO and CO2 inside the covered drums, but these concentrations varied drastically depending on the analytical method, making interpreting the results difficult. Employee PBZ exposure to CO could exceed the NIOSH ceiling limit and ACGIH excursion limit when employees evaluate the covered drums for off-gassing filters prior to disposal. Our results indicate that a possible hazard from CO exposure might exist. This hazard can be easily mitigated by keeping the drums uncovered to prevent the buildup of gases. Maintenance employees reported no symptoms related to their work that would suggest high exposures to CO. On the basis of a scientific literature review and air sampling results, we conclude that the covered drums were pressurized primarily because of H2 formation and that silane was also formed. The disposal of used filters resulting from the silicon wafer grinding filtration process in covered drums can pose a health and safety hazard to employees. Leaving the drums uncovered will help mitigate these hazards. In addition, if employees experience headache, nausea, or confusion, they should promptly report them to the on-site healthcare professional.
Semiconductors; Industrial-factory-workers; Region-8; Gases; Silicon-compounds; Grinding-equipment; Filters; Filtration; Maintenance-workers; Air-sampling; Carbonates; Organic-compounds; Oxides; Analytical-processes; Gas-sampling; Breathing-zone; Storage-containers; Exposure-assessment; Exposure-levels; Exposure-limits; Health-hazards; Hazardous-materials; Hazardous-waste-cleanup; Waste-disposal;
Author Keywords: Semiconductor and Related Device Manufacturing; silicon; silane; hydrogen; carbon monoxide; CO; carbon dioxide; CO2; wafer grinding
7440-21-3; 7803-62-5; 1333-74-0; 124-38-9; 630-08-0
Field Studies; Hazard Evaluation and Technical Assistance
NTIS Accession No.
National Institute for Occupational Safety and Health