The instrument is used for bioaerosol sampling and particle size analysis. It consists of a six-stage cascade impactor, sampling pump and accessories. Impactor has 6-stage disc impactors with different diameters, each plate has 400 small, precisely sized holes located in circular and decreasing in size from stage to stage. The standard sampling flow rate is 28.3L/min. When airflow containing microbial particles enters the top sampling port, microbial particles of different sizes will be impacted on the corresponding agar surface according to aerodynamic characteristics.