In the process of ventilation design, different links are considered according to the characteristics of the project. The purpose of ventilation is to exchange indoor air circulation with outdoor air, so that it can take away indoor pollutants. Therefore, there are always several links that we often meet in the design process：
1. Is make-up air considered in this area? Sometimes, the room has no windows or is set to a fixed window. At this time, if only the air is exhausted, the closed room will form negative pressure, which is not conducive to the removal of harmful gases. At this time, we need to consider the setting of the corresponding make-up air, make-up air location is best to consider the air distribution, leaving no dead angle. Generally, the upper exhaust is adopted and the lower intake is adopted.
2. What is the height of the exhaust fan? In general, upper exhaust can be used to remove waste heat and odor. Specifically, as long as the exhausted gas has a lighter density than air, upper exhaust can be used, and the fan can be placed on the upper part of the room. If the exhausted gas is heavier than the air and will sink, the lower exhaust is necessary. However, the lower exhaust usually does not install the fan in the lower part of the room, but connects the air pipe to the upper part, and removes it through the upper fan, and the lower part opens the air outlet on the air duct.
3. Is emergency ventilation necessary? The conditions of emergency ventilation are more complicated. Generally, the following special area conditions can be considered: the area where the gas gathers to a certain concentration will explode and cause poisoning. There are also substations and power distribution rooms, considering the exhaust of smoke after a fire, and accident ventilation should be considered.
