Study on the time-delay effect of haze pollution in indoor environment

As a frequently occurred phenomenon in the past decade, especially in recent years, hazy weather or haze pollution has become an emergent environmental issue which is highly concerned in many scientific fields in China. Haze pollution not only raises particle concentration indoors during haze episodes by indoor-outdoor air exchange, but also worsens indoor air quality after the episodes due to its time-delay effects. When haze weather passed, the fine particles, which deposited on the walls of ventilation systems and formed dendritic structures, particularly in ducts, would resuspend into the incoming air by flow flushing and other impactions, and then enter into indoor environment. This phenomenon causes a time-dependent delay of indoor haze pollution， i.e.，a relatively long-time pollution duration （with a relatively high concentration） indoors related to the haze episode. However, investigations and analyses are still lack on this problem and similar/corresponding topics.

Considering the time-delay effects of haze pollution on indoor air quality, and indoor particle concentration differences between the durations of haze episode and haze free days，the main aim of the present study is to investigate the deposition, accumulation in short-time spans and resuspension of fine particles in ducts and indoor solid surfaces by employing field measurement, chamber experiment and theoretical analysis.

According to the configurations and features of different surfaces, also with the concerning of the wide-range variations of particle concentration during haze episodes， particle deposition behaviors, their morphologies that adhered on duct walls, inner walls of rooms and furniture surfaces and the resuspension levels will be estimated by using theoretical analysis and experimental test. These analyses will be used to evaluate the deposition characteristics and to provide some suggestions for modifying the local configurations of the ducts, for this may Lead haze particles to easily deposit on some special portions of the ducts, and then it is convenient for timely and effectively duct cleaning after haze episodes. Based on the investigations mentioned above， some important roles or strategies will be recommended for reducing the time-delay effects and time-duration of haze pollution indoors.