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In-depth survey report: evaluation of enclosing hood and downflow room for nanocomposite manufacturing.
Heitbrink WA; Lo L-M; Farwick DR
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 356-16a, 2012 Oct; :1-30
Engineered nanomaterials, specifically carbon nanotubes, graphene platelets, and other ingredients are used to manufacture a nanocomposite paper at this site. National Institute for Occupational Safety and Health (NIOSH), Division of Applied Research and Technology (DART), Engineering and Physical Hazards Branch (EPHB) researchers studied the combined use of a downflow dilution ventilation room and a ventilated booth for controlling worker exposure to dusts that can contain engineered nanomaterials. Fan-powered filter units supplied air from the ceiling, and this air was drawn out of the room through filters located on one wall, just above the floor. This room was used for preparing slurries containing engineered nanomaterials and other ingredients. To produce the slurry, containers of dry powders are placed in the ventilated booth. Then, the containers are opened, and the dry ingredients are quantitatively transferred to a beaker on a weighing scale. After adding the desired mass of material to the beaker, a solvent is added to convert the dry powder to a slurry for subsequent handling outside of the booth. Other activities that can occur in this room include manual cutting of the nanocomposite paper and grinding of the nanocomposite paper in the hood. During this study, an aerosol photometer (Dustrak Model 8533, TSI, Inc,) and a fast mobility particle sizer (FMPS, Model 3091, TSI Inc.) were used to measure concentrations in the worker's breathing zone and near emission sources as a function of time. This time-series data was examined to evaluate whether the operation or process caused noticeable concentration increases as compared to some background period prior to the work tasks or equipment operations that might increase concentrations. In this study and report, background concentrations refer to concentrations measured before the work-place event occurred. Measurements made with an aerosol photometer (Dustrak Model 8533, TSI, Inc,) and a fast mobility particle sizer (FMPS, Model 3091, TSI Inc.) showed that powder weigh out and grinder operations within the weigh out booth did not cause a meaningful increase in aerosol concentrations measured in the worker's breathing zone. In addition, the manual cutting of the nanocomposite paper did not cause a meaningful increase in aerosol concentrations. The low concentration measurements were attributed to the downflow ventilation and the operation of the booth. The downflow ventilation avoided the formation of eddies which can transport air contaminants directly into the worker's breathing zone. The workers positioned the powders and equipment within the booth so that eddies would not transport dust out of the booth. Although the downflow provided by the fan-powered filters appeared to effectively control worker dust exposure, maintenance of this system may become problematic as pressure loss across the filters could not be accurately measured to determine when filters need to be changed. The nanocomposite paper produced at this site is used to manufacture composites. During subsequent manufacturing operations, it is possible that individual nanoparticles could be released if the product is cut. To obtain some preliminary information, a composite containing the nanocomposite paper manufactured at this site was cut using a band saw operating at a nominal surface speed of 5,000 feet per minute. The aerosol photometer and fast mobility particle sizer showed a very large increase in aerosol concentration when the composite was cut. Particle number and mass concentrations increased from 1.76 x 104 particles/cm3 and a mass concentration of 0.05 mg/m3 to 1.71 x 106 particles/cm3 and 3.87 mg/m3. These particles were in the size range from 7 to 100 nm. Further research on this topic is needed to determine whether individual nanoparticles are being released. If composites are being routinely cut by the band saw, dust control measures should be implemented.
Control-technology; Engineering-controls; Nanotechnology; Industrial-equipment; Industrial-exposures; Analytical-instruments; Analytical-processes; Particle-aerodynamics; Particulate-sampling-methods; Airborne-particles; Aerosol-particles; Monitors; Industrial-dusts; Emission-sources; Workplace-studies; Air-contamination; Ventilation-systems; Air-pressure; Air-quality; Air-quality-control; Monitoring-systems; Ventilation; Exposure-levels; Control-methods; Exposure-assessment; Author Keywords: Engineering Controls; Engineered Nanomaterials; Control Evaluation
Field Studies; Control Technology
NTIS Accession No.
National Institute for Occupational Safety and Health
Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division