The flow enters the inlet cowl and accelerates through the six radial slots in the first impactor stage. The cowl eliminates ashes and debris from the sampler. Particles larger than the cut-point of the first stage impact on the precut collection substrate. Then, the air-stream flows through the narrower slots in the second impactor stage, smaller particles impact on the second collection substrate, and so on. The width of the radial slots are constant for each stage but are smaller for each succeeding stage. Thus, the jet velocity is higher for each succeeding stage, and smaller particles eventually acquire sufficient momentum to impact on one of the collection substrates. After the last impactor stage, remaining fine particles are collected by the built-in 34 mm filter.

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