Effects of the human body's thermal plume on pollutant exposure in an indoor environment

The concentration of inhaled contaminants is considerably affected by the airflow and pollutant transport in the vicinity of a human body. The distribution of contaminants in a room can vary significantly, depending on the ventilation system. The thermal plume from the heat generated by the human body can transport contaminants from or towards the human breathing zone. This paper focuses on an analysis of local airflow created by thermal plume and effects of the plume on particulate contaminant distribution. Based on experimental measurements, the effects of thermal plume on both the age-of-air and the particle distribution are analyzed. An environmental chamber equipped with a breathing thermal manikin is used to characterize the interaction between a thermal plume and the overall air motion in the room. The paper provides analysis of the stability of plume when different phenomena distract the airflow. The effects of physical movement, human breathing, and fan-powered air mixing are considered. The results show that the concentration of particulate matter in inhaled air is smaller than the concentration of particulate matter in other parts of the space. For the analyzed cases, correlations are detected between the age-of-air and particle concentration. Results show that locations with larger age-of-air values have a higher concentration of particulate matter of size 0.5 -2.5μm. Also, the analysis shows that the influence of physical movement, breathing, and fan operation weaken the protective upward airflow of thermal plume. However, a considerable upward airflow in the vicinity of the occupant is present even with fan-mixing airflow in the space.