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To get a more comfortable working and living environment, air conditioners and fans are widely used indoor. Considering that indoor air quality is closely related to people’s physical and mental health, a university dormitory is selected to measure indoor particles concentration. The possible relationship between the concentration of particles and the use of air conditioner or fan are explored. The result of this study indicates that, the mass concentration of PM2.5 indoor has a function relationship with the time. This article not only describes the changing regulation of particle’s mass concentration, but also compares the differences of the changing regulation of particles caused by fan system or air conditioner. Introduction People spend nearly 2/3 of the time indoor a day [1]. The quality of indoor air environment seriously affects people's physical and mental health [2, 3]. In order to get a more comfortable working and living environment, air conditioners and fans are generally used indoor. CCTV international site survey has showed that more than 1/5 people stay in fans or air conditioners environment more than eight hours a day [4]. A university dormitory is selected to measure indoor particles concentration in the environment with fans or air conditioners. The possible relationship between the concentration of particles and the use of air conditioner or fan are explored in this paper. Experiments and Methods Experiment subject.The object of this experiment is a room on the 2nd floor in a dormitory. There is a window, a door, six beds and tables (the bed is above the table), an air conditioner, and a fan in it. The indoor arrangement is shown as Fig.1. . Fig.1 Indoor arrangement 3rd International Conference on Machinery, Materials and Information Technology Applications (ICMMITA 2015) © 2015. The authors Published by Atlantis Press 1332 Experiment instruments. A smart dust detector (DUSTTRAK 8520) was used to measure the mass concentrations of PM2.5 and PM10.0.The number concentrations of the indoor particles were measured by a laser particle counter (AEROTRAK 8220). The experimental instruments were placed in the center of the room and the height was 0.8m above the floor Experimental scheme. The experiment includes two conditions: (1) running the fan system seperately; (2) running the air conditioner separately. The experiment of each condition lasts for 120 minutes. Every data is measured every 5 minutes until an hour later. For the fan condition, the fan is working in the largest. For the air condition condition, the temperature of the air conditioner is set at 26°C during every condition. Results and Discussion Concentration characteristics of indoor particles under the fan condition -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 80 100 120 140 160 180 200 220 240 260 280 m as s co nc en tra tio n (μ g/ m 3 ) time (min) PM2.5 PM2.5 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 0 1x10 2x10 3x10 4x10 5x10 6x10 7x10 8x10 9x10 1x10 1x10 1x10 nu m be r c on ce nt ra tio n (c ou nt s/ m 3 ) time (min) smaller than 0.3μm smaller than 0.5μm smaller than 1.0μm smaller than 2.5μm smaller than 2.5μm Fig.2 The dynamic changes of mass concentration Fig.3 The dynamic changes of number of PM2.5 and PM10 under the fan concentration of PM2.5 and PM10 under the fan Fig.2 shows the mass concentration of particles. It can be seen that the mass concentration of PM10 changes relatively flat. However, the change of PM 2.5 mass concentration is volatile with time. Fig.3 illustrates the number concentrations of PM that particle diameter > 0.3μm is much higher than those of the other particles. It can be inferred that when the fan is working, the smaller the particle diameter is, the more violent the airflow are. The number of particles with size of 0.3-1.0μm takes a great proportion in the air, but not the mass. After turning on a fan for 5 minutes, the mass concentrations of particles reaches maximum. After that, the mass concentrations gradually decrease, finally, stay in a steady state. When the fan is closed, all the mass concentration and number concentration of particle is basically in stable trend. From above, it can make some inferences. Turning on a fan in 5 minutes, the airflow indoor is accelerated, the movements of particles flow faster, due to electrostatic interactions and gravity, the particles in the ground or on the object’s surfaces turn the equilibrium state into a dynamic station, making the high concentration of particle in a short time. After the fan works smoothly, it takes time for these particles to establish a new stable state. Concentration characteristics of indoor particles under the air conditioner condition The studying method of the air conditioner is same with the fan, and it can reach the same points. It can also be seen in Fig.4, when the air conditioner began to run, the mass concentration of particles is not significantly reduced. That it need some time for air conditioner to run smoothly may account for it. Fig.5 shows the number concentration of particles. When the air conditioner is turned on, the air temperature indoor reduces, the air flows faster, the movements of particles accelerate. However, the impact of large size of particles is relatively small. Thus, only small size of particles change obviously.

The influence of fan system and air conditioner on indoor particles in university dormitories