When should a red label be attached to a fire alarm system?

A red label is used to indicate that a fire alarm system does not function or is inoperable. This labeling is essential for safety and compliance, as it informs building occupants and emergency responders that the fire alarm system is currently not operational and that they should take necessary precautions. This alert helps prevent reliance on a faulty system during an emergency, which could lead to dangerous situations.

In contrast, the other options relate to operational states or conditions where a red label would not be appropriate. For instance, if a system is fully operational or passes inspection, there is no need for caution labels, as it indicates that the system is functioning as intended. Additionally, newly installed systems should undergo testing and verification processes to ensure functionality before being labeled appropriately, rather than receiving a warning label.