Aerosol dispersion and energy consumption in a mechanically heated and cooled multi-chair dental office with windows routinely opened

Natural ventilation via open windows is a common practice widely applied to dilute aerosols in dental offices for all year around in China, which, however, would modifies air distribution and leads to extra energy consumption for cooling and heating. This study intends to evaluate aerosol removal efficiency and energy consumption in a multi-chair dental office with both mechanical ventilation (MV) and natural ventilation (NV), namely, mixed-mode ventilation (MMV). It numerically investigates the effect of ventilation mode and environmental condition on indoor aerosol distribution and fallow time (FT) duration, as well as energy consumption. The results show that introducing fresh air via open windows in such a mechanically ventilated space results in enhanced airflow mixing and particle dispersion. Compared to six air changes per hour (ACH) MV mode, MMV mode with less than 4 ACH NV does not ensure a reduction in suspended particle count indoors. When NV rate reaches 6 ACH, all compartments show an average reduction of 64.6% in particle counts. However, energy consumption for MMV mode with 6 ACH NV is 3.5 times higher during heating seasons and 2.2 times higher during cooling seasons compared to 6 ACH MV mode. Compared to MV mode with recommended FT of 18–21 min between appointments, MMV mode with 4–6 ACH NV has the required FT of 14–16 min. This study is intended to provide references for clinic managers to balance air quality improvements with energy consumption, thereby achieving a sustainable indoor environment and optimizing operational costs in multi-chair dental offices.