In this paper, the indoor temperature distribution and particle concentration of office room in Shanghai are simulated by numerical simulation, and verified by experiments. Thus, the purpose of this study is to explore the effects of different particle sizes on the settlement and trajectory of floor particles in the under-floor air distribution (UFAD) system. Particles deposited on the surface and floor will again enter the air in a suspended state due to airflow disturbance, which will threaten people's health. This work provides a design basis for reducing the respiratory exposure of personnel in high-polluting sites. The optimal solution of DAS for each target zone is screened, and the linear relationship between the diameter of the protected area and the radius of the cylindrical nozzle is fitted under a different protection factor. The sensitivity of the parameters of DAS to pollution removal at the height of the breathing zone is analyzed, and the findings reveal that increasing the size of the cylindrical nozzle is a more effective protective measure against gaseous contaminants than increasing the air supply velocity. The target zone of DAS is determined by the proposed nonguarantee factor combined with the smallest enclosing circle algorithm. The 3D position of the head of personnel is identified and recorded by the positioning system, and the probability density of the residence time of personnel in each position of the chamber is counted. A positioning system based on Kinect v2 for skeleton tracking is built in a confined test chamber. This work proposes a novel design method for direction air supply (DAS) system, which can protect personnel from exposure to gaseous contaminants during movement. Ventilation systems designed for pollution removal in high-polluting workshops are usually ineffective due to the movement of workers.

Application of the presented research can contribute to improving the health-related aspects of the building environment. Overall, the effects of indoor particles on indoor air quality, including the potential threat of aerosol transmission of respiratory infectious diseases, are non-negligible. Small-sized particles can easily follow the airflow and diffuse to upper parts of the room. The results demonstrate that fine particles (i.e., those with size less than 0.5μm) have a significant impact on the indoor particle concentration, while coarse particles (i.e., with size above 2.5μm) have a greater influence on the total mass concentration of indoor particles. The k-ε two-equation model is applied as the turbulence model in the numerical simulation, while the Lagrangian discrete phase model is adopted to trace the motion of particles and analyze the distribution characteristics of indoor particles. Furthermore, the mathematical modeling method is adopted to simulate the indoor flow field, particle trajectories, and pollutant dispersion process. Based on our analysis, we conduct an experimental study to determine the distribution of indoor inhalable particles of different sizes before and after diffusion under the conditions of underfloor air distribution. In this research, we study standards focused on inhalable particles and indoor environmental quality, as well as analyzing the movement and diffusion of indoor particles. To improve the indoor air quality and control the spread of viruses, the analysis of inhalable particles in indoor environments is critical. After the outbreak of COVID-19, the indoor environment has become particularly important in closed spaces, being a common concern in environmental science and public health, and of great significance for the building environment.

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