Which device would likely be used to control airflow in a duct system?

The Variable Air Volume (VAV) box is specifically designed to control airflow within a duct system. It achieves this by regulating the volume of air that is distributed to various spaces based on the heating and cooling needs of the area. A VAV box can adjust the airflow dynamically, which allows for precise temperature control and energy efficiency in a building’s HVAC (heating, ventilation, and air conditioning) system.

In contrast, a thermostat's primary function is to monitor and control the temperature in a space by signaling the HVAC system when to turn on or off, but it does not directly control the airflow itself. An air filter's role is to improve indoor air quality by capturing dust, debris, and other particulates, and while it is crucial for system efficiency, it does not regulate airflow. A compressor, on the other hand, is a core component of refrigeration systems that compresses refrigerant to circulate through the system but does not manage airflow in ducts. The VAV box is essential for modulating airflow based on real-time requirements, making it the most suitable choice for this application.