An improved apparatus for generating a mist is provided. The apparatus has at least one working fluid supply conduit (66) having an inlet in fluid communication with a supply of working fluid and an outlet in fluid communication with a first mixing chamber. The apparatus also includes a plurality of transport fluid passages (60a,60b), each of which has an inlet adapted to receive a supply of transport fluid and an outlet in fluid communication with the mixing chamber. Downstream of the mixing chamber is a nozzle (72) having an inlet (74) in fluid communication with the mixing chamber, an outlet (78), and a throat portion (76) intermediate the nozzle inlet (74) and outlet (78). The throat portion (76) of the nozzle (72) has a cross sectional area which is less than that of either the nozzle inlet (74) or the nozzle outlet (78). The provision of a plurality of transport fluid passages flowing into the mixing chamber, and the nozzle downstream of the mixing chamber, enhance the atomisation of the working fluid to generate the mist.