Do increased flow rates in displacement ventilation always lead to better results?

Indoor ventilation is essential for a healthy and comfortable living environment. A key issue to discharge anthropogenic air contamination such as CO $_2$ gas or, of potentially more direct consequence, airborne respiratory droplets. Here, by employing numerical simulations, we study mechanical displacement with wide range rates $Q$ from 0.01 0.1 m $^3$ s $^{-1}$ person . For this scheme, cool lower zone established beneath warm upper interface height $h$ , which depends on weak ventilation, find the scaling relation $h\sim Q^{3/5}$ suggested Hunt & Linden ( Build. Environ. vol. 34, 1999, pp. 707–720). Also, $_{2}$ concentration decreases within regime. However, too strong becomes insensitive ambient averaged towards value. At these values concentrations pollutants are very low so further dilution has little effect. We suggest that scenarios arise when vertical kinetic energy associated flow significant compared potential thermal stratification.