Which component is part of an ESS fire alarm system to ensure operation during power outages?

• A. Colorful exterior signage
• B. Glass break detectors
• C. Smart thermostats
• D. Backup power supplies

Answer: (D)

Maintaining fire alarm operation during power outages requires a reliable backup power source. The backup power supplies provide a secondary energy source for the ESS fire alarm system, allowing the panel, detectors, notification devices, and related circuitry to keep working when the main electrical supply fails. This is typically achieved with battery-backed power and, for longer outages, an automatic generator with a transfer switch that seamlessly takes over without interrupting service. The result is continuous alarm and monitoring capability, which is essential for life safety and rapid response.

Other options don’t address staying powered during an outage. Signage doesn’t keep the system energized; glass break detectors and smart thermostats still need power to function, but they don’t guarantee continuous operation when the main power is out.