Field measurements on indoor air quality of a residential building in Xi'an under different ventilation modes in winter

In recent years, China is facing severe haze pollution in winter. More and more newly built residential buildings are installed with mechanical ventilation systems. In order to explore the system's application effect, this study selected a new typical residential building in Xi'an, China, and conducted a series of field measurements on indoor air quality (IAQ) under different ventilation modes. Several indoor pollutants including CO2, PM2.5, HCHO, TVOC, CO, and O-3 were monitored. Four ventilation modes were considered including natural infiltration, window-opening ventilation, and two mechanical ventilation modes with low and high ventilation rates. The ventilation rates and IAQ under different ventilation modes were evaluated and compared. In order to better analyze the causes of some measurement results, numerical simulation was also employed to simulate the air distribution. The results showed that the measured values of the air change per hour of the four ventilation modes were about 0.2 h(-1), 1.2 h(-1), 2.15 h(-1), 2.84 h(-1), respectively. The indoor concentrations of HCHO, TVOC, CO, and O-3 could all be controlled far below the Chinese limit under all ventilation modes. The indoor CO2 concentration under the natural infiltration mode reached 3300 ppm. The window-opening ventilation could only reduce the indoor CO2 concentrations for a short time, and the indoor PM2.5 concentrations were far above the Chinese limit in haze days. The mechanical ventilation system with filter could effectively avoid the influence of haze weather on indoor PM2.5 concentration. But the control effect of CO2 concentration was not satisfactory. The indoor CO2 concentrations under the two mechanical ventilation modes reached 1900 ppm and 1500 ppm, respectively. The simulation results indicated it was caused by the short circuit of airflow. It is suggested that significantly more attention should be paid to the design of air distribution of residential mechanical ventilation. This study is expected to contribute field data for natural and mechanical ventilation modes and also provides a guidance for the optimization of residential mechanical ventilation.