This study numerically investigated the influences of ventilation designs on pollutant removal in a large space with multiple pollutant sources. The types of ventilation include general displacement and local exhaust ventilation with either partitioned or non-partitioned working field. The study demonstrated that the outlet positions and outlet flow rate distribution for local exhaust ventilation are more important than those of the general displacement type. It would be more effective to design local exhaust by placing the outlets on the midstream and downstream of the machines rather than on all the machines. The results also demonstrated that the effect of local exhaust type would not be more superior to the general displacement type due to the large space in plant and multiple pollutant sources such as oil gas pollutant source, mist of metalworking fluid, etc.