A tripartite consortium DEBENE (Deutschland-Belgium-Netherlands), Japan, and France studied the sodium evaporation process of aerosols in a sodium fire. In an inert atmosphere, experimental and theoretical condensation rates were compared and indicated sodium hydride (NaH) to be the foreign nucleus for mist formation. In a normal atmosphere, the physicochemical characteristics of the aerosols produced by a sodium fire and their evolution in containment or in the environment were determined; models enabling the various countries to achieve harmonious results were derived. The proper functioning of the components, guaranteeing perfect operation during and after a sodium fire accident, was tested.