The paper deals with a three dimensional modelling of an experimental device realized in the Department of "Fisica Tecnica" of the University of Rome "La Sapienza" in cooperation with the Italian National Council of Researchers (CNR) in order to investigate the performances of shutter type air curtains as a dynamic barrier against the diffusion of fumes or airborne toxic substances.

This paper presents the results of the numerical simulation on the ventilation efficiency and the residual age of air by using CFD in the underground car park in which the field measurement was conducted as shown in a previous paper. The agreement between the CFD result and the measurement one was observed at most of the measuring points. The detailed distribution of local air change effectiveness was examined with the results from CPD in this paper.