In order to examine the criterion of leak testing of installed filter systems shown in ISO 14644-3: 2005, evaluations of particle concentration at downstream of installed filter systems by particle counters and aerosol photometers were compared, assuming the same upstream concentration distribution. As the result of numerical calculations, although particle counters and photometers detected different penetration rate values, a reasonably good correlation was observed between both instruments within the allowable requirements for the upstream particle concentration distribution stated in ISO 14644-3. A possibility to use the same evaluation criterion for both instruments was also studied. Based on the results obtained, it was found that the same standard leakage evaluation criterion could be applied to the filters with a performance of H14 (BS-EN 1822-1: 2009) or higher. However, for the filters with a performance of H13 and lower, it was considered unreliable to apply the same criterion. Currently, the ISO 14644-3: 2005 is too complicated, different criterion for particle counters and photometers are presented. Moreover, the criterion changes for particle counter at different filter grades used in the tested rooms. The findings obtained in this study will simplify the complexity exists in the current ISO standard.
In this study, the fracture phenomenon of particle impacting with wall was directly observed using a high-speed camera. The results from the experiments indicate that the fracture behavior differs in the impact angle, and there are two types of fracture mode: one is with “Break” and the other with “Chip”. In case of low impact angle condition (less than 70°), there is only “Chip” mode. Furthermore, the effect of the particle impact angle on particle fracture phenomena was also investigated. The results of this study indicate that the particle fracture velocity almost is the same value at impact angles under 45° or higher.