Twin screw extrusion is the preferred process to commercially produce nanocomposites by compounding the nanoparticles and polymer melts. Polymer nanocomposites, which contain nanoparticles dispersed in a polymer matrix, provide improved properties at low filler loadings. Nanoalumina particles recently have been used as fillers to polymer matrix that contributed enhanced physical properties of nanocomposites. Recently, concerns had been expressed that airborne nanoparticles particularly of nanoalumina released during compounding might present serious contamination of the air in the workplace. Researchers with experience in environmental health and polymer manufacturing monitored the compounding process for a model nanoalumina-containing nanocomposite using a TSI Fast Mobility Particle Spectrometer (FMPS). FMPS measurements were taken at background locations, source locations, and operators’ breathing zones; in parallel to the FMPS real time measurement, airborne nanoparticles were collected using polycarbonate filters fitted with filmed grids driven by a personal air sampling pump. Filter samples were analyzed for particle morphology and elemental composition. It was found that the nanoparticle number concentration was elevated during processing. The released nanoparticles are a complex mixture of the individual nanoalumina particles, agglomerates of those particles, polymer fume particles, and perhaps others.