1.The indoor unit needs to be connected to the air duct. 2. Ducts are generally used for air supply with fresh air units, but also for exhaust and circulation with fresh air machines, in order to facilitate the cleanliness of the air and to ensure room temperature! If it is a factory or commercial premises, then we should choose different materials according to the design of the air duct! Exhaust system generally use axial fans and tin ducts! 3. Smaller units do not exhaust, only the air supply and return (that is, you say from the outdoor wind and exchange), there is also a cooling tower with water for circulation! 4. Diffuser is commonly known as the "wind", it is the entire air conditioning system outlet. In order to facilitate the diffusion of airflow, mostly square. Generally not directly with the machine interface, most of the fire soft connection. For the fire level of low places can not be used!