Effects of source emission and window opening on winter indoor particle concentrations in the severe cold region of China

Indoor particles are affected by both indoor particle sources and outdoor particles penetrating into the indoor environment. Some human behaviors such as opening windows, cooking, and smoking influence indoor air quality strongly. Indoor particle sources increase the indoor particle concentrations by generating considerable amounts of particulate matters. Opening windows can increase the exchange efficiency of indoor and outdoor particles. In this study, the effects of indoor particle source emission and opening a window on indoor particle concentrations were estimated for the severe cold region of China using tests in a room-size chamber. Indoor and outdoor fine particulate matter (PM_2.5) mass concentrations and particle number concentrations from 0.3 to 10 μm were measured simultaneously in different test conditions. An indoor source was simulated using an aerosol generator to discharge dust, which was intercepted by indoor air conditioners. Indoor particle concentrations increased rapidly when the indoor source was active, and longer emission time led to greater growth. After ending indoor particle emission, indoor particle concentrations decreased due to infiltration and deposition, and opening the window can promote that decrease. Decay rates were greater for 2.5–10 μm particles because loss by gravitational settling is dominant for larger particles. When the window was opened, particle decay rates became extremely high; up to 19.09 h⁻¹ for 2.5–10 μm particles and up to 9.73 h⁻¹ for PM_2.5.