Pressure vessels are widely used to store liquefied gases under pressure at ambient temperatures. From a safety point of view, it is desirable to know what happens when a small breach appears in the vessel, when the stored gas is toxic or flammable. In this paper, we deal with the dispersion of propane when the breach is located in the liquid part. As a consequence the liquid will escape from the tank and evaporate during its mixing with the ambient air. We describe the fragmentation of the liquid into droplets when it is suddenly depressurised. Sizes and velocities of these droplets are evaluated, assuming that the liquid will flash. Then these droplets will interact with the ambient air which can contain humidity. Evaporation, condensation and turbulence are taken into account. Results are presented.