Fine particle concentrators for inhalation exposures—effect of particle size and composition

This paper presents the development and evaluation of ambient fine particle concentrators for conducting animal and human exposure studies. These systems utilize the technology of virtual impactors to concentrate particles in the range 0.15–2.5 μm. Ambient particles are first drawn at 5000 1 m−1 through a preselective inlet that removes particles above 2.5 μm. Subsequently, the remaining aerosol is drawn through a series of virtual impactors, which increase particle concentration by a factor of about 10 and 30, for human and animal exposures, respectively. Results from the experimental characterization of the concentrators showed that the concentration enrichment process occurs without any distortion in the size distribution and chemical composition of the sampled ambient aerosols. Furthermore, labile constituents of fine particles, such as volatile ammonium nitrate are preserved during this process.