Abstract: A device, composition, and a process for a hybrid blend of inert gas and mist produced for fire protection by local or total flooding. The method mixes ultrafine water mist, preferably less than 20 microns diameter produced by atomization and an inert gas such as nitrogen. A homogeneous hybrid composition discharges from a swirling flow mixer-injector device. The hybrid composition extinguishes a fire source in reduced time by simultaneous and synergistic cooling with the mist and inerting with the inert gas. After extinction oxygen remains at a safe level of 12.5-15% (V). The high-velocity inert gas flow of 35-75 mph velocity in the mixing-injector column formed by an exit in the mixer-injector device entrains the low-velocity mist flowing out of atomizer. The device creates a swirling, high-speed, and expanding flow of the hybrid composition inside the fire protection volume at ambient pressure.