Comparison of infiltration of different particle sizes and influencing parameters

Abstract

The size fractional distribution of indoor and outdoor particles was investigated to understand how particle size, air change rate, building airtightness, and meteorological parameters affect particle infiltration behavior. The experiments were performed for two apartments, one without airtightness intervention and the other after sealing the window gaps. Although the correlation analysis showed that the indoor PM trend was highly dependent on outdoor conditions, different penetration behavior for different particle sizes was noticed. Despite the absence of indoor sources, the size fractional distribution of particles in the indoor and outdoor environment did not follow the same pattern. Moreover, airtightness somehow reduced the envelope effective leakage area and slightly decreased the indoor/outdoor ratio and infiltration factor for all particle sizes; however, it did not affect the relative infiltrability. The highest penetration rates were observed in the size range of 0.3–1.0 μm and the lowest rates were in the 2.5–10 μm range. Although with particles greater than 0.3 μm, the infiltration of fine particles was higher than that of coarse particles, the infiltrability of PM < 0.3 was slightly lower than PM0.3-1.0, probably due to the penetration dominated by the concentration gradient. Particle size, envelope airtightness, and outdoor source were the main factors that governed fractional particle infiltration, overshadowing the effect of meteorological parameters. Furthermore, window airtightness decreased the indoor-outdoor PM correlation, especially for coarser particles. It caused approximately a 1-h lag-time between the indoor and outdoor PM trend, a positive point in case of accidental increase of outdoor levels.