Type C curtain dampers are used when velocities are __________.

Type C curtain dampers are specifically designed to handle medium to high air velocities in HVAC systems. This capability allows them to effectively manage airflow in environments where the air movement is more rapid, which can prevent issues such as noise, turbulence, and pressure drops that occur with improper damper selection.

These dampers are constructed to ensure proper sealing and minimize leakage at these higher velocities, which is essential for maintaining system efficiency and performance. Using a damper rated for medium to high velocities ensures that it can withstand the forces exerted by the moving air without compromising its integrity or functionality.

Options associated with low to medium velocities do not align with the specifications of Type C dampers, as they are not necessary for airflows that do not present the same challenges. Similarly, classifications involving high to extreme velocities or variable conditions would require different types of damper systems designed for those specific applications, as the needs in those scenarios would significantly differ from those addressed by Type C dampers.