Which capability must an auxiliary fan be capable of?

• A. Running only when commanded by VO.
• B. Switching off automatically if main ventilation fails totally.
• C. Storing data locally.
• D. Operating at reduced power in recirculation.

Answer: (B)

The key idea is automatic safety interlock behavior: an auxiliary fan must be capable of switching off automatically if the main ventilation fails totally. When the primary airflow is lost, continuing to run the auxiliary fan can create unpredictable air movements, risk backflow, or spread contaminants in an uncontrolled way. An automatic shut-off provides a known, safe state and supports the emergency ventilation plan by not relying on a human operator to react in a potentially dangerous moment. The other options describe manual control, data storage, or operation under recirculation, none of which address the fail-safe isolation that’s required in a total main-fan failure.