Local exhaust ventilation systems are an effective means of removing hazardous substances that may cause health problems for workers, such as dust and toxic gases generated during work, at work sites such as factories that handle various chemical substances. It is known that the side suction hood of the local exhaust system, especially the capturing hood, is susceptible to turbulent flow currents existing around it, and the suction capacity of the hood is reduced. In addition, when designing a local exhaust ventilation system, it is necessary to satisfy the control velocity stipulated by laws and regulations, depending on the type of hood and the state of hazardous substances. This control velocity considers the general turbulent flow, so when designing an capturing hood, if the turbulent flow is small, the required exhaust air flow volume may be excessive, which poses a problem in terms of energy consumption. Therefore, in this study, three types of capturing hoods for working on a workbench are studied, and the required exhaust air flow volume to suppress leakage when disturbance air flows in different directions with respect to the opening of the hood was determined. From the results, regardless of the size of the hood, when the hood opening surface is disturbed in the crosswind direction, the amount of exhaust air volume required to suppress the leakage is larger than when the turbulence occurs in other directions. In addition, in this experiment, in the case of providing a local exhaust at the welding fume site, if the performance requirements of the local exhaust system are not uniformly determined by the control velocity, and the control velocity is flexibly operated according to the properties of the material, it is expected to contribute to solving the problem of poor welding caused by welding shield gas interference.

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