The certified reference material NMIJ CRM 5721-a has been developed for use in the calibration and control of the precision of particle size measuring instruments including a differential mobility analyzer (DMA). This CRM is provided as a water suspension of monodisperse polystyrene latex (PSL) particles. The certified values for number average diameter and particle size distribution width of PSL particles are 100.5 nm±2.6 nm (the number following the symbol±indicates the expanded uncertainty with a coverage factor of 2) and 2.4 nm±1.0 nm, respectively. The certified values are determined by the electrical mobility analysis with a DMA, and are metrologically traceable to the International System of Units (SI), expressed as nanometeres. Having the particle size distribution width as a certified value is one of the notable features of this CRM. This CRM can be used not only for size calibration but also for validation of sizing resolution.
In the previous work, two types of installed filter leak tests described in ISO 14644-3; aerosol photometer method and light-scattering airborne particle counter (LSAPC) method, were examined by considering the difference in the characteristics of each measuring instrument. It was found that the same leak detection criterion (LDC) could be applied to filters above H14 grade in both test methods. Hence, the LDC of the aerosol photometer method could be applied in the LSAPC method for H14 or higher grade filters. However, LSAPCs have different optical, flow and electrical systems, resulting in different counting efficiency functions (CEFs). Furthermore, ISO 21501-4 allows LSAPCs to have a certain range of CEF. Therefore, it was necessary to ensure whether the same LDC could be applied in the installed filter leak test when applying different measuring instruments admitted by 21501-4. In this study, using theoretical calculation, the determination of threshold size, which makes the LDC unification possible between the two test methods, was further discussed, and penetrations detected by LSAPC with various CEFs were evaluated. It was concluded that 0.3 µm is the most suitable threshold size, and the same LDC studied in the previous work could be applied to the LSAPC with different CEFs.