Type A curtain dampers are primarily used when restrictions of the __________ in the airstream is not a concern.

Type A curtain dampers are specifically designed to minimize the resistance in the airflow when they are in operation. They consist of flexible blades that allow for a smooth and unrestricted passage of air, making them ideal in scenarios where there is no concern about airflow restrictions. These dampers typically do not interfere with the airstream, enabling efficient ventilation and airflow management in various HVAC applications.

The mention of "stacked curtain blades" relates to the mechanism of how Type A dampers operate, as they often feature multiple layers of blades that can fold or stack together, allowing for flexibility in airflow control without compromising performance.

In contrast, concerns regarding airflow, temperature, or fan speed are not pertinent in the context of using Type A dampers. These dampers are particularly valuable when maintaining a steady and unobstructed airflow is prioritized, hence why the correct answer focuses on the operational characteristics of the dampers in relation to airflow restrictions.