Building simulations are used to investigate building performance and design the building systems optimally. In particular, the air exchange between zones and with the environment has a pivotal role in modern ventilation system design. Nevertheless, the model of the airflow becomes difficult for the modeler, motivated by the complexity of the grid that has to be modeled. IDEAS, a Modelica library, includes components for thermal multi-zone models of buildings as well as models for heating, ventilation, air conditioning and other elements that interact in the same model. The actual version, however, does not include proper components to model airflows in an efficient way. The simulated air includes humidity and several trace substances, but the detailed transportation of those substances between the zones currently does not exist in the standard components. The purpose of this paper is twofold. At first, the article intends to describe the development of new components that will be used to implement the air multi-zone model into the existing thermal multi-zone model in IDEAS. The second goal is to integrate the newly developed components with the actual components of the library to share parameters that are needed to generate a grid of air pressure, reducing the modeling steps. The developed components are based on the pressure difference of the connected elements and include vertical air shafts, orifices, infiltration defined by the effective air leakage area, windows and doors.Keywords: Modelica, IDEAS library, building simulations, Multi-zone airflow, contaminant transport