Most penetrating particle size

The models described in the following use only one parameter for the cleaning efficiency, which is thus a simplification that must be kept in mind when using these models. This works quite well as long as the efficiency value is the smallest one—e.g., the efficiency for the most penetrating particle size or the efficiency for the most penetrating gas concentration. 

HEPA and ULPA filters have been developed. In the CEN EN 1822 1998 test method, the filter s efficiency is determined for the most penetrating particle size (MPPS). Depending on the filter s total level of separation and leakage, the filter is classified as HIO, Hll,.. ., H14 and U15, U16, or U17. HEPA filters are commonly used for inlet air in the pharmaceutical, optical, and food industries. 

Most penetrating particle size, in depth filtration theory, 11 340-341 Motens, molecular formula and structure, 5 127t... 

Martin, S.B., Moyer, E.S., 2000. Electrostatic respirator filter media filter efficiency and most penetrating particle size effects. Appl. Occup. Environ. Hyg 15, 609-617. 

The particle concentration efficiency tests are used for the various grades of high efficiency air filters (HEPA, ULPA), and use the sub-micrometre aerosols described in earlier paragraphs. The procedures are described in detail in BS EN 1822, which also highlights the Most Penetrating Particle Size (MPPS) as probably the most important performance characteristic. 

Table 6.3 shows the many standards for efficiency testing of HEPA and ULPA filters. New classifications have been defined for both types of filter according to EN 1822 and these are given in Table 6.4. The system is based on letters and figures in the same way as for coarse and fine filters according to the EUROVENT Classes, with H standing for HEPA and U for ULPA. The filters are then divided into eight classes from HIO to U17, depending on their efficiency at the most penetrating particle size (MPPS) and the size of the leaks.

The grade efficiency T of most collectors can be expressed as a function of the aerodynamic particle size in the form of an exponential equation. It is simpler to write the equation in terms of the particle penetration Pf (those particles not collected), where the fractional penetration = 1 — T, when T is the fractional efficiency. The typical collection equation is... 

Following the evaporation of water from the lipid nanodispersion applied to the skin surface, lipid particles form an adhesive layer, applying occlusion to the surface [17,40]. Therefore, the hydration of the stratum comeum may increase, which can facilitate drug penetration into deeper skin strata and even systemic availability of the drug. Occlusive effects are strongly related to particle size. Nanoparticles have turned out 15-fold more occlusive than microparticles [17], and particles smaller than 400 nm in a dispersion containing at least 35% high-crystallinity lipid proved to be most potent [41]. 

Ksec = 0 when the molecule hydrodynamic radius is higher than the mean pore diameter. KSEC is 1 with small molecules, which can easily penetrate into the pores. The most important parameters influencing resolution are the pore volume, pore size distribution, and particle size. The separation domain is between the exclusion volume Va and the inclusion volume ( V0 + Vp). 

As a result of the particle size-dependent properties the accumulation mode particles having highest penetration efficiencies and lowest deposition rates tend to enter indoors most efficiently and remain suspended there, thus substantially contributing to indoor exposures. Another implication is that the particle size distribution indoors differs significantly from that outdoors, even in the absence of indoor sources. Finally particle infiltration varies from home to home, resulting in higher variability across homes in indoor particle concentrations compared to outdoor concentrations. 

According to Fig. 10.1, XRD is one of the most frequently applied techniques in catalyst characterization. X-rays have wavelengths in the A range, are sufficiently energetic to penetrate solids and are well suited to probe their internal structure. XRD is used to identify bulk phases and to estimate particle sizes [9]. 

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