Experimental Study On Indoor Particle Pollutants And Their Regularity Of Transport In Residential Buildings

With the development of economy,pollution of particulate in the indoor and outdoor residential buildings is becoming more and more serious.However,people spend about half a day staying in residences,are vulnerable to be in danger of indoor particulates.At present,the concentration of indoor particulate matter,especially the number concentration in residential buildings is relatively scarce.Thus,understanding the status of indoor particulate pollution is the most important step.In addition,as the transport regularity of particulate matter varies with the particle size and the air change rates,it is of great significance to control indoor particulate matter by obtaining the knowledge of penetration factor,deposition rate,resuspension with particle size and air change rates.This paper adopts the questionnaire survey to obtain the characteristics of the layout of residential buildings,the characteristics of indoor particulate matter as well as the factors affecting the transport regularity.In addition,11 typical households are selected for natural and infiltration conditions to obtain indoor and outdoor particulate concentrations,and indoor to outdoor ratio（I/O）and infiltration factor with the characteristics of particle size changes.Finally,this study selects the real room for experimental testing and conducts an analysis of particle deposition rate,penetration factor,resuspension with the particle size and the air change rates.The main conclusions are following:（1）Time when people stay in residential buildings is extended,there are still 53%of people spending in houses for more than 10 hours per day.People are becoming increasingly conscious about indoor particulate pollution;however,they lack quantified cognition.Thus,the using of fresh air ventilator and air purifiers are irrational to a great extent.（2）The average indoor and outdoor PM₁₀0 and PM_2.5.5 concentrations in winter in xi,an exceed WHO standards.The indoor and outdoor particulates are mainly composed of fine particle（d_p<1.0μm）,with an order of magnitude up to 10⁷ particles/m³.The proportion of PM₁ accounts for more than 60%of PM₁₀.（3）Under natural conditions,the average values of I/O with diameters of less than0.5μm and greater than 8μm are greater than 1,and the average values of I/O between0.5 and 8.0μm is less than 1.They keep stable firstly and then decrease,then increase again with increasing particle size.The lowest values occur in the range of 2.5⁵.0μm.The average value of I/O of PM₁ is greater than 1,while the average values of I/O of PM_2.5.5 and PM₁₀0 is less than 1.The infiltration factor for number decreases firstly and then increases and goes down with the particle diameter.The maximum value occurs in the range of 0.5-1.0μm.The infiltration factor for mass is F(PM₁₀)>F(PM_2.5)>F（PM₁）,the relationship between indoor and outdoor is R(PM₁₀)<R(PM_2.5)<R（PM₁）.（4）Under the infiltration conditions,the average values of I/O is less than 1 when the particle diameter is less than 8.0μm,and it is greater than 1 when the particle size is greater than 8.0μm.The values of I/O decrease firstly and then increases with the increase of the particle size,and the lowest occurs within the range of 0.5-2.5μm.The average values of I/O of PM₁,PM_2.5,and PM₁₀0 are less than 1.Besides,infiltration factor for number increases firstly and then decreases with increasing particle size,and the maximum value appears at 0.3μm.The infiltration factor for mass is F(PM₁₀)<F(PM_2.5)<F（PM₁）,the relationship between indoor and outdoor is R(PM₁₀)<R(PM_2.5)<R（PM₁）.（5）The deposition rate fluctuates with increasing particle size.The air change rate has a greater influence on particles below 2.5μm,but it exerts no effect on particles larger than 2.5μm.Small particles are more sensitive to stability of indoor air flow.Stable conditions can inhibit the deposition of particles smaller than 1.5μm.The density of the particles affects the deposition rate of the particles.The higher the density is,the greater the deposition rate is.The heat emitted by the low-power electrical appliances has almost no effect on the deposition rate of the particles.（6）Resuspension is an indoor source that cannot be neglected,and its emission decreases with increasing particle size.When the number concentration of particulates is greater than 0.5×10³ particles/cm³,coagulation occurs for the fine particles.Penetration of particles through the window gap need to consider the deposition rate due to inertial impaction in the gap.The result is the ratio of the vertical and horizontal window gaps on the penetration factor is not obvious.