In the AHU builder it is imperative to determine which way / direction the air is flowing.
There are some fan sections that can be utilized for Return air to the unit, and another section is used for supply air from the unit. The symbols designated on the sides of the components allows the designer to configure the AHU as needed for the project, and allow this component to be rotated to suit the connection to supply or return ductwork. As for the symbol, I don’t believe it can be turned off, but I will investigate further to your question.
There are some fan sections that can be utilized for Return air to the unit, and another section is used for supply air from the unit. The symbols designated on the sides of the components allows the designer to configure the AHU as needed for the project, and allow this component to be rotated to suit the connection to supply or return ductwork. As for the symbol, I don’t believe it can be turned off, but I will investigate further to your question.