TSI’s suite of cascade impactors can collect particles with aerodynamic diameters (cutpoints) from 10 nm to 10 µm, in 3 to 13 different size fractions, and at flow rates of 2, 10, 30 or 100 L/min. The number of stages determines the size resolution of the collected samples, and consequently determines the level of detail of the data generated from the quantitative analysis of these collected samples. MOUDI II impactors have rotating stages. When the stage is rotated relative to the nozzle plate, the impacted particles are deposited in a more uniform manner across the impaction surface. This increases the amount of particle mass that can be collected, reduces the probability of particle bounce and re-entrainment, and optimizes quantitative analysis of the collected samples.