Which of the following is commonly used as a fire protection measure in buildings?

The fire alarm system is a critical fire protection measure in buildings because it is designed to detect smoke, flames, or other indicators of a fire and alert occupants and emergency services. It plays a vital role in ensuring the safety of building occupants by providing early warnings that can facilitate timely evacuations and minimize the potential harm from fires. Fire alarm systems often include various components such as smoke detectors, heat detectors, pull stations, and audible and visual alarms that work together to ensure that a fire situation is identified and communicated effectively.

Other options, while important for building functions, do not serve the primary purpose of fire protection. For example, HVAC systems are primarily designed for heating, ventilation, and air conditioning rather than fire detection or protection. Elevator shafts, despite being designed for safe transport, do not actively protect against fires; they can even present hazards if not properly managed in the event of a fire. Similarly, electrical panels are crucial for managing electrical supply but are not specifically designed as a fire protection measure. In contrast, a fire alarm system is a proactive tool that helps mitigate fire risks by promptly alerting individuals to the presence of a fire.