Fire extinguishing systems tend to be optimized by impinging a reduced amount of water, with controlled droplet diameter distribution. This paper investigates the minimum water flow rate required for extinguishing a fire experimentally. A gas burner is placed under a water mist nozzle to expose the fire to a controlled water discharge, gradually increasing the volumetric flow rate injected. The water mist consists of a full cone jet, generated thanks to a single nozzle, with a 100 to 300 µm particle diameter. One of the specific characteristics of water mist is the injection of small particle diameters. Thanks to their high exchange surface between droplets and the ambient, the evaporation rate is increased, which contributes to facilitating fire extinction. The main mechanisms involved in the extinction process are the cooling of the reaction zone and the reduction of the oxygen concentration by putting steam directly in this reaction zone. Some research works were published to correlate the required water flow rate to extinguish a fire but based on small-scale tests, typically with HRR lower than 50 kW. This paper aims to check whether or not these relations can be applied to higher heat release rates and higher flow rates in order to determine the critical water flow rate that extinguishes the fire. A set of normalized parameters have been used to comprehend the extinction phenomenon and to analyse the experimental data. The tendency of averaged results shows a predictable extinction rate and consolidates literature data.