Investigation On The Relationships Of Indoor And Outdoor Aerosol Concentration In Air-conditioned And Non-air-conditioned Rooms

Urban air pollution has receiving more and more attentions with the rapid increase in industrialization and urbanization in China in current days. Now there are about 400 million people live in cities, and this number is expected to grow steadily until mid-21st century. Some investigations show that particulate emissions have exacerbated the air pollution in large and medium size cities resulting in visibility reduction and public health concerns, and indoor air quality thus become an important problem since people spending the majority of their time indoors.The relationships between indoor and outdoor particle concentrations have been studied since 1950s, the results showed that the there exist a large regime of indoor to outdoor ratios (i.e., I/O ratio)of particle mass concentration, and the ratios were affected obviously by many factors such as the characteristics of internal and external sources, the activities of the people living or working indoors, etc. Previous results indicated that the number concentrations indoors were more effective to evaluate the health effects and indoor air quality rather than the mass concentration.The time series of indoor and outdoor PM₁₀, PM_2.5 and number concentrations are monitored in four types of rooms in Shanghai city in winter and summer, they are naturally ventilating room, mechanical ventilating room, the wall-mounting air-conditioned room and the central air-conditioning room. The relationship of PM₁₀, PM_2.5, number concentrations and indoor to outdoor ratios between indoor and outdoor of the rooms are analyzed and discussed, respectively. The testing data show that in naturally and mechanical ventilating rooms, the variation of aerosol concentrations (including PM₁₀, PM_2.5 and number concentrations) are dominated by the ambient ones, inner aerosol emission is the main source of wall-mounting air-conditioned rooms, but ir central air-conditioning systems, indoor PM_2.5 levels are primarily affected by the ambient aerosol concentrations. The monitored data also show that time delay exist in central air-conditioning rooms, naturally and mechanical ventilating rooms.An numerical simulation scheme is introduced to estimate the relationships between indoor and outdoor particle concentrations for the four types of rooms, the numerical results shows the time delay and the main features of the time series of the four types of rooms well comparing with the testing data, it also confirms that the numerical simulation can be used to predict the indoor particle concentration by using the outdoor aerosol concentration curves.