Effects Of Human Thermal Plume On Biological Particle Diffusion In Hospital Surgical Microenvironment

In a highly clean hospital operating environment,bacteria-carrying particles released by medical staff is one of the main pollution sources in operating rooms,which may cause Surgical Site Infection in patients.The coupling of human thermal plume and air flow affects the directional distribution of air flow,which leads to more complex distribution of biological particles.In this study,the effects of different ventilation conditions on the diffusion of biological particles were systematically studied.In this study,based on the full-size surgical laboratory and self-made fever manikins,the airflow velocity measurement and bioaerosol diffusion experiment were carried out in the centralized vertical laminar air supply mode of smallpox.Bacillus subtilis was used as the model bacterium in the experiment,and the source emission concentration was 1.1×10⁷CFU/m L.The concentration distribution under ventilation was systematically measured.Based on the results of relevant experiments,the numerical simulation was verified to ensure the reliability of numerical simulation results.Then,the interaction between six air supply velocities（V₁=0.01 m/s,V₂=0.1 m/s,V₃=0.15 m/s,V₄=0.2 m/s,V₅=0.25 m/s,V₆=0.3 m/s）and human thermal plumes under ceiling concentrated vertical laminar air supply was studied.The spatial distribution of biological particles was also discussed.The results show that when the air supply velocity was less than 0.2 m/s,the air supply cannot effectively reduce the diffusion of human thermal plume.The human thermal plume will move up the leg of the human body and disturb the airflow in the surgical area,leading to the diffusion of biological particles above the patient,increasing the possibility of biological particles deposition on the surgical table and increasing the potential risk of surgical site infection.When the air supply velocity reaches 0.2 m/s,the influence of human thermal plume on the airflow in microenvironment can be ignored.In the commonly used operating room,the air supply velocity of 0.2 m/s can effectively provide a clean operating environment.In this study,the same method was used to further explore the coupling law and distribution characteristics of biological particles between four ventilation systems（ceiling concentrated vertical laminar flow ventilation,horizontal laminar flow ventilation,contour surrounded vertical laminar flow ventilation and temperature controlled ventilation）and human thermal plume at the designed air supply velocity.The results show that temperature-controlled ventilation can effectively reduce the airflow disturbance caused by human thermal plume and maintain the air cleanliness of the surgical microenvironment compared with the other three ventilations.The vertical laminar flow ventilation is better than the horizontal laminar flow ventilation,and the vertical laminar flow ventilation centered on ceiling is better than the vertical laminar flow ventilation surrounded by contour.The air cleanliness control that affects the hospital surgical microenvironment is closely related to the air supply form,air supply speed and air supply temperature.This study provides quantitative data reference for the control and design of biological particles in hospital surgical microenvironment.