In the present paper, the influence of the initial inclination angle of the jet on the efficiency ofa vertical downward air curtain is analysed. The air curtain device was mounted over anoverture, in the wall between two equal contiguous rooms, with the typical dimensions of adoor. Between the two rooms there is a temperature difference, simulating a situation wherethere is the intention of isolating a comfortable room from a warmer outside environment.The sealing efficiency provided by the air curtain was determined, for different inclinationangles and initial velocities of the air jet, through the tracer gases technique. The velocity andtemperature fields were obtained, in interest zones, with a set of low velocity thermalanemometry probes. For some of the studied configurations, flow visualizations were carriedout using an infrared thermographic camera.Some interesting findings about the influence of the orientation of the jet in the performanceof the air curtain device are presented.