FIELD-BASED INVESTIGATION ON VERTICAL DISTRIBUTION OF AIRBORNE PARTICULATE MATTER IN MULTI-STOREY BUILDINGS

The aim of the study is to quantify the traffic generated particle number concentration levels (PM2.5; PMwith diameter ? 2.5?m) at various heights of a typical high-rise building in close proximity to a majorexpressway in Singapore. A 22-storey naturally-ventilated high-rise residential building located about15m away from a major expressway was selected for the study. Three floors of the building wereselected for the PM2.5 measurements namely, the fourth storey which represented the lower floors, tenthstorey which represented the mid floors and seventeenth storey which represented the upper floors ofthe building. Objective measurements namely particle count, wind speed, wind direction, ambienttemperature and relative humidity were conducted at the selected floors. The experimental results showthat PM2.5 mean number concentration was highest at the mid floors of the building when compared toits upper and lower floors during peak and off peak hours. This could be due to the tree canopiesplanted alongside the expressway which deflected some of the traffic-polluted air from the lower levelstowards the mid floors of the building as it traversed from the expressway towards the building and atthe same time allowing the mid floors to peak earlier than other floors. Although the lower floors wereclose to traffic emissions, the mean particle number concentration was lower than the mid floors due toloss from deflected traffic-polluted air and also the tree canopies act as a filter and trap PM2.5 particlesas the particles traveled from the expressway through the leaves towards the lower floors of the building.The upper floors had the least fine particulate matter number concentration due to dilution.