This paper presents design and performance evaluation of virtual impactors that can be used to concentrate aerosol particles. One single-nozzle and two multi-nozzle (4-nozzle and 18-nozzle) virtual impactors were designed and constructed as aerosol concentrators in this study. Evaluations of the aerosol concentrators were performed at different ratios of the minor flow rate to the total flow rate (minor-to-total flow ratios). It was found that the particle concentration factor, rootStk(50) and the cutoff diameter are sensitive to the minor-to-total flow ratio as well as the number of nozzles. These results will be useful for high-volume air sampling applications at the low pollutant concentration area.