Occupational Exposure to Carbon Nanotubes and Nanofibers

Table 6–7. Engineering controls to reduce CNT and CNF exposuresProcess/activityA. Pilot and research developmentoperationsPotential exposure source and recommendedcontainment of exposure*Exposure Source: Synthesis of CNT and CNF by fluidized-bed, chemicalvapor deposition, etc.: a) collection/harvesting after synthesis, b) powdertransfer, c) cleaning reactor, d) removal of CNT and CNF from a substrate,e) purification and/or functionalization of CNT or CNF [note: potentialexposures are generally to small quantities of CNT and CNF (i.e., µg,mg) compared to exposure to larger amounts (e.g., kg) during full-scalemanufacturing/synthesis (see C below)].Exposure Controls: a) laboratory fume hood (with HEPA filtered exhaustwhen warranted), b) HEPA-filtered exhausted enclosure (glove box), or c)biological safety cabinet. Local exhaust ventilation (LEV) may be requiredwhen opening reactor and during harvesting.B. Research laboratories Exposure Source: Handling (e.g., mixing, weighing, blending, transferring)small quantities (e.g., µg, mg) of CNT or CNF powder or during sonicationof a CNT or CNF liquid suspension.Exposure Controls: a) laboratory fume hood (with HEPA filtered exhaustwhen warranted), b) HEPA-filtered exhausted enclosure (glove boxisolator), or c) biological safety cabinet.C. CNT and CNF manufacturingand synthesisExposure Source: Synthesis of CNT and CNF by fluidized-bed, chemicalvapor deposition, etc., including: a) collection/harvesting after synthesis,b) drum and bag filling, c) powder transfer, d) cleaning reactor, e) removalof CNT and CNF from a substrate, f) purification and/or functionalizationof CNT or CNF [Note: potential exposures are generally to large quantities(e.g., kg) of CNT and CNF].Exposure Controls: Dedicated ventilated room with HEPA filtered exhaust,and/or LEV at source of exposure with HEPA filtered exhaust. Examples:ventilated bagging/weighing station and/or laminar down-flow booth ornon-ventilation options such as continuous liner off-loading systems forbagging operations. Ventilated bag dumping stations for product transfer.See footnotes at end of table.(Continued)NIOSH CIB 65 • Carbon Nanotubes and Nanofibers61