Page:NIOSH Manual of Analytical Methods - Chapter N.pdf/4



Figure 2. Schematic of filter seal region showing paths of airflow through leak. When a leak is present, the observed dust deposit indicates loss of material near edge of filter. Some of this lost material is found deposited on the cassette wall. The flow path through or around the backup pad appears to take some combination of Paths A, B, and C [2]. 182