The global spread of COVID-19 in 2020 had a significant impact on the population. Healthcare workers who have unpreventable contact with infected individuals are at high risk of infection. We therefore proposed “infection control methods in high-risk environments” and demonstrated that appropriate placement of suction devices in otorhinolaryngology examination rooms is effective for aerosol control [Takada M, Fukushima T, Ozawa S, Matsubara S, Suzuki T, Fukumoto I, Hanazawa T, Nagashima T, Uruma R, Otsuka M, Tanaka G: Sci Rep. 12(1), 18230, 2022]. As a further study of the previous research, this study analyzed the specific environmental factors that contribute to reducing the risk of infection by optimizing the manner in which suction devices are set up. The models of a patient and doctor were placed in an examination room. A steady flow of 2.5 m/s was applied to the patient’s mouth as exhalation. Aerosol diffusion was analyzed using computational fluid dynamics. The optimization parameters were the position and angle of suction inlet, and suction speed. The objective evaluation was the “maximum number of particles aspirated from the suction inlet”. A total of 150 designs were tested, and the search for the optimal positions was performed in the examination room. The optimization results showed that the maximum particle removal rate was 98.6%. There were six cases in which the particle removal rate was at least 98%. These positions were within the range of x = 0.120 to 0.159 m in the horizontal direction from the patient’s mouth to the suction inlet. The suction inlet was placed laterally in front of the patient, along the trajectory of the particles emitted from the patient’s mouth. Particle removal rates of over 98% at various suction speeds indicates that the position and direction of the suction inlet are more important than the suction speed. The adjustment of suction devices based on the results of this study would help reduce the risk of infection in healthcare settings.