The air distribution is determined by the system architecture. The air in the unit is directed to the main outlets by using doors and kinematic parts (actuator, levels, cables, central gear, etc.). Some HVACs are separated in distribution so that the passenger can have a different setting to the driver:
In manual air conditioning systems, flaps inside the device are used to control the head/lap/foot air distribution. The flaps are actuated from the control panel using cables.
Automatic air conditioning systems apply the same principle, but they are fitted with motor driven mixing flaps that adapt the air distribution to the context and the history of system usage.