A constant air volume (CAV) system supplies a fixed amount of air to the conditioned space, regardless of the cooling or heating demand. In contrast, a variable air volume (VAV) system adjusts the airflow rate based on the changing load requirements. VAV systems are more energy-efficient and flexible, as they can modulate airflow to match the occupancy and temperature fluctuations. However, CAV systems are simpler and less expensive to install, making them suitable for smaller, less complex applications.