Age of air and air change effectiveness in operating rooms: comparison of air distribution configurations

Studying fluid dynamics in an operating room has a key role to achieve the right air quality conditions inside, for different purposes, and thus the patient comfort, the correct air distribution (distinguishing infected or not infected patients), the recirculation of contaminants and so on. One of the most relevant parameters to take into account is the age of air, defined as the mean time that a particle takes to go from an inlet point to the considered point. This parameter can be employed to evaluate the air change effectiveness inside the room. In this study, the effect of two distinct arrangements of recovery grids for the air outflow and two different positions of the lighting systems are considered. The computational fluid dynamics software ANSYS Fluent is used to solve the partial differential equations governing the mass transport, air velocity components, turbulence, energy, and age of air in order to evaluate the changes in terms of age of air and air changes effectiveness in critical zones of an octagonal operating room. Inside the room, the presence of four people of medical staff and the patient is considered too. The results show critical differences among the distinct considered arrangements, highlighting how relevant the operating room fluid dynamics is. The lowest mean age of air (136 s) and the highest air changes effectiveness (108 %) among the simulated configurations occur in the case of vertical return grids and vision lamp on patient bed and when the xy vertical plane located at the center of the room is considered.