The aim of this paper is to show the possibilities offered by Scilab/Xcos to model and simulate aeraulic and HVAC systems. In particular we develop a new Xcos module combined with the use of Modelica language to show how aeraulic systems can be modeled and studied. In this paper we construct a reduced library composed by few elements: hoods, pipes and ideal junctions. The library can be easily extended to obtain a more complete toolbox. The developed library is tested on a simple aeraulic circuit.