A major point of concern in using tunnel ventilation (or any type of ventilation) is the air inlets. In fact, for proper ventilation they are practically much more important than the outlet fans.

Tunnel ventilation is based on the principle of the cooling effect of air velocity. We therefore let air in on one side of the house, eventually through a cooling pad, and remove it from the other side.

If the air inlets are mounted in the side walls of the house, the jet of air will have to enable the fresh air to reach the middle of the house, before it starts moving towards the fans. If not, there will be an area with high temperature and still air in between the inlets at the middle of the house. At this triangle-shaped area, mortality will be higher.

To avoid this triangle of death, we must create a jet of air flow, strong enough to reach the middle of the house. The higher the speed of the incoming air, the more jet will be created, and the further the air will be brought in before it is bending towards the fans.

This speed of incoming air is determined by the pressure difference between inside and outside of the house, the so-called negative pressure. This presssure is determined by the relation of fan speed and inlet opening. The faster the fans turn or the less the inlets are opened, the higher the air speed will be. This actually means that for proper control, the opening of the inlets must be related with the amount of air moved, to control proper negative pressure and accurate air speed coming in.

To avoid the risk of this triangle of death happening, some additional inlets can be placed in the wall closest to the triangle.

To a lesser extent, a similar triangle can also occur at the opposite side of the house if the fans are located at the side walls instead of the head wall.