Water curtains have been widely used in industries to prevent the release of heavy gas. It is very important to understand the dilution mechanism of water curtains and explore the setting parameters of the water curtains in a limited space. In this paper, experiments were conducted to explore the factors related to the dilution efficiency of water curtains. The results indicated that the dilution efficiency of a water curtain was about 80%. The dilution efficiency of fan spray nozzles was about 6% higher than that of cone nozzles. The dilution efficiency of single layer water curtains was about 1.7% higher than that of double water curtains. The dilution of a water curtain was the most efficient when the water spray nozzles were installed 1.2 m high. The higher the water pressure, the greater the dilution efficiency. The dilution efficiency of water curtains decreased with the distance between water curtains and the release source. When the CO2 was released from 40 L/h to 160 L/h, the dilution efficiency would decrease from 88-89% to 78-79%. (C) 2016 Elsevier Ltd. All rights reserved.