DEPOSITION MECHANISM AND INFLUENCING FACTORS OF PARTICULATE MATTER PENETRATION IN BUILDING ENVELOPE

Particulate matter is a complex mixture of extremely small particles and liquid droplets. It is a diversepollutant class whose excessive presence in indoor air contributes to an array of adverse health andmaterial-damage effects. The size of particles is directly linked to their potential for causing healthproblems. Particles are classified according to their diameter into three size modes: ultrafine (less than0.1 ?m), accumulation (0.1-2 ?m), and coarse (larger than 2 ?m).The following deposition mechanisms of particulate matter through crack should be considered: gravitydeposition (caused by the gravity of particles), Brown diffusion deposition (caused by the diffusion ofparticles) and inertia impaction. Some studies point out that inertia is not an important mechanism asparticle with enough inertia to be lost by impaction was also likely to be lost by settling, but in L or Z ormore bend cracks, if the crack is not long enough for particle to settling by gravity, inertia can not beignored. It has been found that the air exchange rate plays an important role in the rate of transmissionof outdoor air contaminants into the indoor environment, particle size and crack height were anothertwo main factors that governed fractional particle penetration. Besides the crack material is anotherimportant factor that influence the particle deposition in the crack of all size distribution. By analyzingthe above items, the over all penetration of particle penetration through the building envelops canobtain.