The effect of door opening on air-mixing in a positively pressurized room: Implications for operating room air management during the COVID outbreak.

The effect of the built environment on the predominant indoor airflow patterns is significant. To protect the healthcare workers at the front line from the outbreak of COVID - 19, it is necessary to understand the transmission dynamics of the virus, which has been shown to depend on indoor airflow patterns. In hospital operating rooms (ORs), design requirements pose a unique challenge as the positive pressure in the OR can facilitate virus spread into adjacent spaces, shall a COVID-positive patient require a surgical procedure. Moreover, the turbulent vortexes from door motions could independently increase the probability of virus escape from the OR to the adjacent corridors. Therefore, to obtain critical knowledge about the alteration of flow fields due to door movement in a positively pressurized room and quantify the air mixing across the door, a series of experiments were conducted in a controlled chamber. The results demonstrate significant impacts of the door opening on the airflow patterns. Increased alterations near the door and vortexes penetrating far into the chamber with multiple doors openings warrant further study of the indoor airflow dynamic under door motion. This experimental study proposes an algorithm to quantify the air exchange due to a standard door opening and quantifies this exfiltration of contaminated air up to 2 air changes per hour, that is 10 of the chamber supply airflow rate. The algorithm to quantify the dissipated air quantity and the analyses of interaction between initial conditions and door openings contribute to the originality of this paper.