Studying the effect of indoor sources and ventilation on the concentrations of particulates in dining halls

The impact of ventilation on indoor particulate pollution is highlighted by numerous studies. The aim of the present study is to examine the influence of ventilation on the levels of particulate concentrations found in dining halls where a large number of students are accommodated. Indoor particulate sources were also quantified and their influence on the particulate concentrations was examined. Measurements were conducted in four University dining halls, which are located in different parts of the city of Athens. Indoor and outdoor CO 2, PM1, PM2.5 and PM10 concentrations along with the number of occupants and smokers were measured in each dining hall during the accommodation of the students. Measurements were repeated for five working days in each dining hall. Ventilation rates were estimated by applying a methodology that involves the solution of the mass balance equation for the CO2 concentrations. The indoor particulate production rates were estimated by performing consecutive numerical experiments with the Multi Chamber Indoor Air Quality Model (MIAQ). Median CO2 concentrations ranged between 1043 μg m-3 and 1590 μg m -3 and ventilation rates ranged between 0.58 h-1 and 5.15 h-1. The respective values for PM1 ranged between 8.6 μg m-3 and 22 μg m-3, for PM2.5 between 17 μg m-3 and 60 μg m-3 and for PM10 between 24 μg m-3 and 78 μg m-3. The Pearson correlation coefficient between the log transformed ventilation rates and the PM10 concentrations were found to be -0.6. Median values of the total production rates were found to range between 100 μg min-1 and 5500 μg min-1 and are highly correlated with the number of occupants (Pearson correlation coefficient 0.86). Examination of the origin of the particulate sources indicated that, in the majority of cases, re-suspension is more significant than combustion sources. Significant short-term variation (one hour time interval) of the various sources was also observed. Even though the production rates were significantly elevated, the measured particulate concentrations were moderate due to the high air change rates obtained. These findings support the results of other studies that highlight the significance of ventilation in environments where indoor sources are prominent.