What are the three units of the airflow system?

• A. Thermostat, humidistat, and vent
• B. Indicating and control panel, a pinwheel sensor unit, an airflow remote alarm unit
• C. Filter housing, duct, and sensor
• D. A damper actuator, a fan, and a controller

Answer: (B)

In airflow systems, you typically have three functional units that cover monitoring, display/control, and alerting. The indicating and control panel serves as the hub, showing status and allowing operators to adjust settings. The pinwheel sensor unit directly measures airflow speed, providing the actual flow data the system relies on. The airflow remote alarm unit picks up these readings and can trigger alarms remotely if airflow drops below safe levels or if a fault is detected. Together, these three units ensure you can monitor airflow, control it, and be alerted to problems quickly.

Other options mix in environmental controls (like temperature or humidity controls) or simply list structural components (duct, filter housing) or drive components (damper, fan, controller) that don’t correspond to the dedicated three-unit airflow monitoring and safety setup described.