Display omitted •Comparative study of human thermal plume under different air supply velocity.•Simulated flow fields agree well with experiment.•Human thermal plume affects the diffusion of bacteria-carrying particles.•The range of air supply velocity for effective control of thermal plume is proposed. In the operating room (OR), ventilation and thermal plumes can affect the distribution of bacteria-carrying particles (BCPs). Especially in the operating microenvironment, the development of human thermal plumes cannot be ignored. Therefore, in this study, six different air supply velocities were used to study human thermal plumes and the diffusion of BCPs. The numerical simulation based on computational fluid dynamics was verified by experiments, and the realizable k-ε turbulence model and Lagrangian particle tracking model were used. The results show that the interaction of the thermal plumes and ventilation significantly affected the diffusion of BCPs in the operating area, which cannot be ignored. The maximum thermal plumes in the ORs are markedly higher than those in other rooms. The strong thermal plumes caused BCPs to reach the operating area and infect the wound of the patient. For most ORs with a vertical unidirectional air supply, ventilation and thermal plumes achieve a good offset when the air supply velocity reaches 0.25 m/s. In addition, increasing the air supply velocity alone cannot effectively control the effect of thermal plumes on BCPs. This study can provide a practical guideline for controlling the diffusion and distribution of BCPs in ORs.