Representation of cad air outlet and smoke inlet

The cad air outlet and smoke inlet are shown as follows:

In cad, s stands for air supply outlet and r stands for air return outlet. Air return ports are mostly rectangular, while air outlets are usually square. The flue is composed of more than two sections of flue pipes connected end to end. The flue pipe is a rectangular pipe with two open ends, with a flat mouth at the lower end and a square mouth at the upper end, which matches the flat mouth at the lower end of the previous flue pipe.