之所以这么设计，是因为所有被采集的微粒（不管体积大小、形状和密度怎么不同）都按照空气动力学原理分级。这种分级，直接对应于微粒在人体肺部的沉积情况。

• Designed so that all particles collected, regardless of physical size, shape, or density, are aerodynamically sized and can be directly related to human lung deposition.