Indoor PM2.5 concentrations in residential buildings during a severely polluted winter: A case study in Tianjin, China

Severe haze weather in recent times in China has drawn global attention and growing public concern over implications to people's health. This study aims to investigate the effects of infiltration and indoor pollution on the level of PM2.5 concentrations in residential buildings. Using a DustTrak II aerosol monitor, PM2.5 concentrations were measured in a typical residential building in Tianjin with different openings to the external environment. When the openings had a void of 10 mm, indoor PM2.5 concentration was similar to that of outdoor. When the indoor PM2.5 concentration reached its peak, the Indoor-to-Outdoor ratio (I/O) was 0.67-0.89 with a delay compared to the outdoor PM2.5 concentration. Higher outdoor wind speeds were associated with higher I/O ratios. With well-sealed windows and doors, PM2.5 concentrations decreased irrespective of the changes occurring outdoor with a decay rate of 0.002 min−1. With regard to the effects of indoor pollution, smoking could make the indoor PM2.5 concentrations rise rapidly to a level of 1280 μg m−3. Kitchen PM2.5 concentrations rose while cooking up to 3000 μg m−3, which largely depended on the method of cooking. Kitchen ventilator was able to control the pollution fairly quickly and reduce the impact on adjacent spaces. Other human activities such as walking, dressing, and sweeping were responsible for an increase in PM2.5 concentration by almost 33%.