A personal nanoparticle sampler (PENS) that simultaneously collects respirable particles (< 4 μm) and nanoparticles (< 0.1 μm) has recently been developed and calibrated in the laboratory. This study aims to evaluate the performance of the PENS in the workplace, and to determine the exposure characteristics during selected metalworking operations. Metal polishing/buffing, spot welding, and milling operations were selected to represent sources of solid metal particles, fume aggregates and metalworking fluid mists, respectively. In each operation, personal samples of a side-by-side PENS and SKC respirable dust aluminum cyclone were taken concurrently with ambient particle number size distribution measurements. The PENS-measured respirable particle mass concentrations (PM 4 ) showed remarkable accuracy with respect to the reference SKC cyclone, regardless of particle type. The PENS-derived nanoparticle effective densities agreed reasonably well with the bulk densities expected for the substrate and materials in use. During the metalworking operations, the nanoparticle mass concentrations (PM 0.1 ) were poorly associated with the PM 4 but strongly correlated with the ambient nanoparticle number concentrations (PN 0.1 ), due to the persistent, elevated levels of nanoparticles formed during the operations. Overall, these results suggest that the PENS is applicable for use in the workplace to assess respirable and nanoparticle personal exposure, and that metal polishing/buffing, welding and milling generate a considerable amount of nanoparticles.