Which system is essential for illuminating exit signs during an emergency?

The system that is essential for illuminating exit signs during an emergency is the emergency generator. This system provides reliable backup power to operate essential lighting and safety systems when the primary power source fails, which is critical during emergencies such as fires or other evacuations. Exit signs play a vital role in guiding occupants safely out of a building, and if there is a power outage, the emergency generator ensures that these signs remain illuminated, helping individuals find their way to safety without confusion.

In contrast, the HVAC system is primarily designed for heating, ventilation, and air conditioning, and while it can contribute to maintaining a safe environment, its role is not directly related to emergency lighting. A public address system is important for communication during emergencies but does not provide illumination. The smoke control system helps manage smoke movement within a building to enhance safety, but it does not activate exit signs. Therefore, the emergency generator is the sole system designated to ensure that exit signs remain operational and visible during critical situations.