Validating AIM-Based Instrumentation and Associated Measurement Techniques - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 336

Fig. 10.64 Three concepts developed by Svensson and Berg for creating abbreviated versions of
the NGI (rNGI) ( From [ 59 ]— courtesy of M. Svensson )
their investigations of the rNGI [ 59 ]. Their “internal filter” or “nozzle-filter” design
(Fig. 10.64b ), already mentioned in connection with the evaluation undertaken by
Daniels and Hamilton (Fig. 10.45 ), was developed and introduced immediately
after stage of interest in the seal body to be able to capture the SPM . It should be
noted that the remaining stages (after the filter) to the micro-orifice collector (MOC)
were still present in the seal body during the measurements with this abbreviated
configuration. This arrangement guarantees an identical flow-time profile if a filter
with sufficiently low air low resistance is used, which is important in the context of
DPI testing.
In the alternative so-called external filter or outlet filter design (Fig. 10.64c ),
Svensson and Berg reconfigured their rNGI so that flow exiting the abbreviated