The present invention is a push-pull ventilation hood having a push device to obtain a push air flow and a pull device to exhaust contaminant flow with an exhaust opening and the two devices properly coordinated with each other, wherein, when the push flow flows through a contaminant source, a contaminated flow of the push flow is exhausted through the exhaust opening. Based on the design process according to the present invention, a push-pull hood with the highest efficiency of push velocity can be designed and the push-pull hood can economically and effectively control the contaminant source.