A convergent/divergent gas nozzle atomizes a liquid provided through a lid delivery tube having an aperture which is centered within a central gas conduit of an upstream mixing block connected to the nozzle. The aperture of the liquid delivery tube is located just upstream of a narrowed throat of the nozzle. The throat of the nozzle is dimensioned such that its inside diameter is equal to the outside diameter of the liquid injector tube. A spout is located at the discharge end of the nozzle which has an inside diameter equal to two times the inside diameter of the throat. This nozzle displays superior performance, providing an extremely fine mist having high momentum. This nozzle is particularly well-suited to fire extinguishment.