Oil and gas explosions threaten the process of industrial protection and personal safety, and explosion risk control/reduction has always been an important issue. As a clean and efficient fire-extinguishing agent, water mist has been evaluated via small-scale tests as a potential efficient material for reducing explosion hazards. To deepen the understanding of large-scale explosion mitigation using actual water mist, which is typically used for fire suppression, a series of experimental tests were conducted using a large explosion vessel (with a 1.5 m x 1.5 m section and a 10 m length). Explosion characteristics flame propagation process and speed, explosion overpressure, and explosion overpressure rise rate were determined and analyzed based on the measured data obtained using a Phantom high-speed camera, flame sensors, and pressure sensors, respectively. Two different types of water mist nozzles, different constraints of the vessel and set locations of the nozzles, as well as water mist additives were considered. The results indicated that both the characteristics of the water mist spray and the installation locations of the nozzles have significant effects on the explosion mitigation. In addition, it was found that the K2CO3 additive can double the explosion mitigation effect of water mist using nozzle A, however, this effect is weaker than that when using nozzle B without K2CO3. Therefore, the effect of K2CO3 additive on the explosion mitigation is weaker than of the change in the water mist characteristics. These results will be relevant for further understanding the process safety of explosion mitigation using water mist under large-scale conditions and for the optimum safety design of water mist explosion mitigation systems. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.