Analysis of PM2.5 indoor-outdoor ratio in lobby floor according to configurations of entrance

Outdoor PM2.5 has a continuous and significant effect on the indoor environment, and lobby floors, in particular, can be exposed to high concentrations due to entrance doors and greater airflow rates than other floors. In this study, the PM2.5 indoor-to-outdoor (I/O) ratio for lobby floors was evaluated according to the operation type and configuration of entrance doors. Airflow analysis was conducted for an office building with multi-zone network simulation, and the I/O ratio was evaluated for different entrance strategies according to the occupant traffic schedule. This study analyzed door configurations with and without vestibules using swinging doors and revolving doors. As airflow analysis results, the neutral pressure level is located at 40% of the total height of the building. The pressure difference across the envelope of the lobby floor was less than the top floor, whereas the airflow was the greatest within the building. As contaminant analysis results, PM2.5 I/O ratios reaching a steady state for the single-type (S-S, S-R) was higher than the box and combo-type (B-S, B-R, C-S, C-R) due to vestibule. Entrances consisting of a single door with no vestibule are directly connected to the outdoor environment and can be exposed to PM2.5 concentrations equal to or higher than outdoor levels. However, the boxed doorway with a vestibule was exposed to concentrations closer to the outdoors, with a maximum I/O ratio of 1.024 when there was no difference in operating time between the two doors. This indicates that the vestibule strategy is meaningless in a scenario where both doors open and close simultaneously. Therefore, architectural methods to design door configurations and additional measures to control door operations are needed to ensure and manage indoor air quality in lobbies.