Displacement ventilation has been considered a good f unction of ventilation since it can provide good indoor air quality ( IAQ) and save energy. Recently it has al so been used in commercial buildings.However , if the floor of the room is not clean enough and is covered wit h some dust , t he f resh air sent from t he floor level will make t he dust airborne and influence indoor air quality. This paper is to st udy t he influence of dust on floor on the IAQ of displacement ventilated room. Because it was difficult to measure the initial dust quantity and particle size , experimentally , the comp utational fluid dynamics ( CFD)
met hod was used in this work. The Euler2Lagrange met hod was used to simulate t his case. The dust concent rations at different supply air velocities and different particle sizes were st uied and t he deposition of dust was compared as well . The result indicated t hat the quantity and particle size of dust on floor should be considered when choosing t he mode of ventilation.