How to choose a profile for different fabric air duct has technical concerns. In general, the air duct can be divided into normal pressure state and negative pressure state. Under normal pressure, the common section shapes are circle, semicircle, 1 / 4 circle, bow, and sector, while under negative pressure, triangle and rectangle are commonly used. Profile introduction under atmospheric pressure: 1. Circular, if there are not too many requirements for an appearance with space height allows, we suggest to choose this kind of air outlet profile. The air outlet area is larger, and the air output is more, so it is more time to change the indoor air. 2. Semicircle, if the height is not allowed or it can be used in the case of aesthetic requirements. 3. 1 / 4 round, small space, or affected by indoor environment, installation location, and other factors can be used in this way. 4. If the space is too small and the semicircle can't be installed, you can only ...