Why does the air flow not change when you switch from defrost to floor?

When you switch from defrost to floor ventilation in a vehicle, the air flow remains consistent because both settings utilize the same blower motor and ducting system. The direction of airflow is altered by changing the position of blend doors that redirect the air, but the overall volume and pressure generated by the blower remain unchanged. This design ensures that airflow is efficient and responsive, allowing for quick adjustments to temperature and comfort.