This paper describes the experimental study of ventilation efficiency for commercial kitchens. We investigated an air conditioning and ventilation system which has high efficiency and can maintain a comfortable environment in the working space with a minimum amount of necessary ventilation air. The results are as follows: (1) In the case of outdoor air being supplied from the bottom of the hood, 60-70% of the outdoor air is exhausted by the hood. (2) Airflow distribution above the gas range is comparatively stable in summer and intermediate seasons, updraft above the gas range goes straight to the exhaust hood when outdoor air is supplied from the top of the gas range. In winter, updraft above the gas range is strongly effected by the outdoor air from the hood, and there is dispersion in the updraft direction. (3) The capture ratio of the combustion gas by the exhaust hood is over 80% in summer and intermediate seasons. The capture ratio becomes higher when the output heat from the gas range is larger.
