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 356-17a, 2012 Nov; :1-22
The study site produces aligned carbon nanotubes in an enclosed reactor (Easy Tube 3000, First Nano, Ronkonkoma, NY). Carbon nanotubes are produced so that they are aligned in one direction on a substrate. These are termed "aligned carbon nanotubes" and they stand on end like the bristles on a brush. Aligned carbon nanotubes can have different physical properties in longitudinal as opposed to other directions (Lan, Wang, & Ren, 2011). This property is used to enhance the electrical and mechanical characteristics. Hazard control for this reactor is largely integral to the equipment's design and is intended to contain dangerous air contaminants. Ventilation is used as a secondary, redundant control measure that removes any process leakage, thermal decomposition products from the reactor exterior, and heat from the enclosed spaces around the reactor. The vertically aligned carbon nanotubes are formed on a substrate. The carbon nanotubes can be spun into a thread that may replace copper wire. Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted a study at this site to evaluate the ability of the Easy Tube 3000 reactor to control worker exposure to carbon nanotubes and to determine whether spinning of the vertically aligned carbon nanotubes into a fiber or thread emitted carbon nanotubes into the workplace air. Air flows in the Easy Tube 3000 system were measured with a hot-wire anemometer (Velocicalc plus model 8386, TSI Inc., Shoreview MN). These direct reading instruments were used to monitor particle number and mass concentrations in the worker's breathing zone and near active production processes: a Fast Mobility Particle Sizer spectrometer (FMPS, Model 3091, TSI Inc.), the Condensation Particle Counter (CPC, Model 3007, TSI Inc.) and an aerosol photometer (DustTrak, Model 8533, TSI, Inc.). Air samples were collected to determine the elemental carbon (EC) concentrations (NIOSH method 5040) and the number concentration of fibers (NIOSH method 7402) on the worker and near the processes we studied. The concentration measurements suggested that the operation of the equipment did not contribute to air contamination in the workplace. Individual fibers were not detected in the workplace air, and elemental carbon concentrations were less than 1 microg/m3. The number concentrations of particles smaller than 100 nm were less than 20,000 particles/cm3, which is typical of ambient air pollution (background). Total mass concentrations were less than the typical PM10 concentrations reported by the local air pollution control agency. However, there were some brief concentration spikes that exceeded 0.1 mg/m3 for periods of 3-4 seconds. Such peaks could be caused by process leakage or the re-suspension of dust in the sampling hose. These results indicate that the Easy Tube 3000 was effectively designed and built to prevent process emissions into the workplace. Furthermore, the static pressure in the systems enclosure was -0.03 inches of water relative to the room; which should prevent leakage out of the enclosure.
Control-technology; Engineering-controls; Nanotechnology; Industrial-equipment; Industrial-exposures; Analytical-instruments; Analytical-processes; Particle-aerodynamics; Particulate-sampling-methods; Airborne-particles; Aerosol-particles; Emission-sources; Workplace-studies; Air-contamination; Ventilation-systems; Air-pressure; Air-quality; Air-quality-control; Ventilation; Exposure-levels; Control-methods; Exposure-assessment; Electrical-properties; Mechanical-properties; Physical-properties; Equipment-design; Control-equipment; Fiber-deposition; Fibrous-bodies; Air-flow; Measurement-equipment; Analytical-methods; Air-sampling; Air-sampling-techniques; Monitors; Industrial-design; Industrial-dusts; Leak-prevention;
Author Keywords: Engineering Controls; Engineered Nanomaterials; Control Evaluation