A numerical study is dedicated to the influence of the different dynamic and geometrical parameters on the sealing efficiency of a downward-blowing air curtain device, which is installed between two contiguous rooms with distinct ambient temperatures. The numerical simulation is based on the two-dimensional solution of the differential equations for the conservation of mass, momentum and thermal energy, using the k-epsilon turbulence model with two-layer wall functions. The performance of the air curtain is expressed by two parameters, the sealing efficiency and effectiveness, which provide the assessment of the energy savings predicted. The results allow a global, yet detailed characterization of the airflow pattern and provide guidelines for the appropriate operation of such devices. (C) 2006 Elsevier B.V. All rights reserved.