Comparative analysis of indoor air quality in offices with different ventilation mechanisms and simulation of ventilation process utilizing system dynamics tool

Keeping COVID-19 pandemic in perspective, good indoor air quality (IAQ) and adequate ventilation are imperative to minimize risk of virus spread, besides other poor IAQ related risks. Thus, present study is focused on evaluation and comparison of ventilation rates (VRs) in office buildings with different ventilation mechanisms. Two-season (summer and winter) data of indoor CO2 was collected, and VRs were calculated adopting three methods i.e., transient mass balance, steady-state and decay method, and were then input in system dynamics-based (SD) model for finding best method for the calculation of VRs. In the last part, simulations were used to calculate the optimum VRs to keep indoor CO2 levels below recommended limits. Results showed statistical difference (p < 0.05) of indoor CO2 among buildings and between seasons. Although better VRs were observed in mechanically ventilated offices, it is to be noted that windows in naturally ventilated offices were observed to be closed (to maintain thermal comfort) and thus naturally ventilated buildings were not operated as per design provisions. Moreover, transient mass balance method was found to be more accurate approach for VRs estimation. Furthermore, it was found that to limit indoor CO2 levels below 1100, 800 and 700 ppm, minimum VRs should be maintained as 10, 16 and 20 l/s/person respectively.