Culverts are located within the space and are therefore considered the last element of a ventilation system. It is faced with the end user and in this aspect, it is the most important element of the system. In the relevant literature, the distribution of the air in the space, in other words, determining the locations and types of the grilles are named as one of the most difficult tasks of the whole ventilation technique. Therefore, the successful fulfillment of this task requires great experience and expertise in terms of both project design and manufacturing.

According to some researches, 70% of ventilation related problems are caused by culverts. It is not possible to set precise rules for the selection of the grille for every situation. Difficulties are encountered, especially in spaces with complex geometric dimensions with high heating and cooling loads. Very low and very high ceilings, halls with balconies, spaces with hanging beams or variable ceiling heights, concert halls, etc.