Infiltration factor

Equation (3) is also written as Cai = Fm[ Ca, with Fm( is defined as the infiltration factor. The infiltration factor describes the fraction of ambient pollution that penetrates indoors and remains suspended. 

The correlation only measures whether the time pattern of indoor concentrations track outdoor concentration trends, it does not provide information on how much a pollutant infiltrates in the indoor environment. In the RUPIOH study, outdoor and indoor nitrate concentrations correlated well in three of the four cities (Fig. 5). However, the infiltration factor was very low, ranging from 0.05 to 0.13. 

Many studies have used the infiltration factor (Flnl), defined as the fraction of outdoor particles that penetrate indoors and remain suspended [11], Compared to the I/O ratio, a major advantage of the use of the infiltration factor is that it is not affected by indoor sources. Equation (3) describes the factors that influence it, which includes both penetration and decay rates. 

Fig. 6 Mean infiltration factor of PM2.5 in relationship to season and region of Europe. Source Hanninen et al. [9]...

Much lower infiltration factors were found for coarse particles than for PM2.5 in four European cities (Table 1). Infiltration factors were estimated from linear regression analyses of simultaneously measured indoor and outdoor coarse particle concentrations. The lower infiltration of coarse particle is consistent with lower penetration and higher decay rates of coarse particles due to gravitational settling and impaction, see Sect. 3. Studies conducted in the USA have reported substantially lower infiltration rates for coarse particles as well [17, 18]. 

Infiltration factors for UFP assessed by total particle number counts were somewhat lower than for PM25 in the four European cities included in the RUPIOH study (Table 1), but higher than for coarse particles. A large Canadian study in Windsor, Ontario in which total particle number counts were measured with PTraks reported infiltration factors of 0.16, 0.26, and 0.21 in the first summer, winter, and second summer, respectively, with a large variability for individual homes [19]. The lower infiltration of ultrafine particles is consistent with lower penetration and higher decay rates due to diffusion losses compared to accumulation mode particles. 

Table 1 Infiltration factors estimated as regression slope for the relationships between indoor and outdoor 24-h average concentrations of different particle metrics from RUPIOH study [13]...

PM2 5 is a complex mixture of components derived from multiple sources. Major components of PM2 5 include secondary inorganic components (sulfate, nitrate), elemental carbon and organic carbon. Infiltration factors and indoor sources differ for these components, as illustrated in Table 1. 

In contrast, for nitrates low infiltration factors were found in the RUPIOH study (range 0.05-0.13) and a study in California homes (infiltration factor 0.2) [18]. The low infiltration is due to the volatility of ammonium nitrate, resulting in a shift towards the gaseous components ammonia and nitric acid upon infiltration because of temperature and relative humidity changes [31]. Nitric acid has high deposition on walls, resulting in a further shift of the equilibrium [31]. 

The large variability of PM2.s infiltration factors reported may further be due to different composition of PM across locations. In locations with relatively high sulfate and EC contributions, higher infiltration factors can be anticipated than in locations with high nitrate and OC concentrations. 

Chen C, Zhao B (2011) Review of relationship between indoor and outdoor particles I/O ratio, infiltration factor and penetration factor. Atmos Environ 45(2) 275-288... 

The k = 2KpAp /r value acting as a proportionality factor in Eq. (2) is called a infiltration factor [7], This factor was found from experimental values of 1 and t using the following formula ... 

A situation often investigated is when no particles are generated from indoor sources for suitably long periods and the only contribution is from outdoor air. The indoor-to-outdoor concentration ratio of the particles is then equivalent to the infiltration factor (Tinf), which is defined as the equilibrium fraction of ambient particles that penetrates indoors and remains suspended [30] ... 

When exposure is repeated, the allergen binds between two adjacent IgE molecules. This causes release of inflammatory mediators (histamine, leukotrienes, chemotactic factors). These act locally and cause smooth muscle contraction, increased vascular permeability, mucous gland secretion, and infiltration of inflammatory cells (neutrophils and eosinophils). However, histamine can also be released by non-IgE-mediated mechanisms (e.g., due to exposure to certain fungi). 463... 

Obviously, the sensors have to be installed in a correct and representative place in the process. Determining an optimal installation of sensors for measuring environmental conditions in large halls is not a simple task. Many different factors have to be taken into account. The main place where a certain climate is to be maintained is given priority. Secondly, the influence of infiltration and radiation from surrounding surfaces must be considered. 

Where there is no mechanical supply or extract, factors are used to estimate possible natural infiltration rates. Empirical values may be found in several standard references, and the CIBSE Guide ([2], A4) covers this ground adequately. 

An important component of the inflammatory state in adipose tissue in obesity comes from the infiltration of the tissue by macrophages. These are likely to be attracted through the secretion by adipocytes of MCP-1 and MEF. The macrophages in turn secrete factors which both directly add to the total production of inflammatory agents by adipose tissue and also catalyse the production of such agents from adipocytes - and perhaps preadipocytes as well. 

COPD is a chronic inflammatory disease that results from prolonged and repeated inhalation of particles and gases, chronic (or latent) infection or an interaction of these factors. In many cases, the inflammation persists even when the exposure (in most cases smoking) is stopped. Prominent among the infiltrating leukocytes are neutrophils, CD8+ lymphocytes (Co-receptor for the T-cell receptor. CD8+ is specific for the class IMHC protein. It is expressed on the surface of cytotoxic T-cells and natural killer cells.) and CD68+ monocytic cells (A lysosomal antigen. All cells that rich in... 

Thermal-Gradient Infiltration. The principle of thermal-gradient infiltration is illustrated in Fig. 5.15b. The porous structure is heated on one side only. The gaseous reactants diffuse from the cold side and deposition occurs only in the hot zone. Infiltration then proceeds from the hot surface toward the cold surface. There is no need to machine any skin and densification can be almost complete. Although the process is slow since diffusion is the controlling factor, it has been used extensively for the fabrication of carbon-carbon composites, including large reentry nose cones. 

Under water scarcity, the two factors, salinity and sodicity of the irrigation water must be considered together for a proper evaluation of the ultimate effect of the water on the infiltration rate that generally increases with increasing salinity of the irrigation water and decreases with either decreasing salinity or increasing sodicity. 

There was a discrepancy between water salinity limits for the three locations, which may be attributed to factors related to difference in soil texture and stmcture. This affects soil infiltration capacity and water retention. These soil hydrologic characteristics influence salt development in the soil profile, which affects plant... 

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