What is a key feature of fire alarm systems?

A key feature of fire alarm systems is the requirement for both audible and visual notifications to effectively alert occupants of a potential fire. This dual notification system ensures that all individuals, regardless of their hearing ability, can receive warnings and evacuate safely. Audible alarms, such as sirens or bells, provide a clear sound cue, while visual notifications, often in the form of flashing lights, serve those who may be hearing impaired or in situations where auditory signals might not be effective, such as in noisy environments.

In contrast, the other options do not encompass the essential features of fire alarm systems. For example, fire alarm systems are designed for both indoor and outdoor use depending on the environment in which they are installed, ensuring comprehensive safety coverage. Additionally, fire alarms generally rely on a power supply, whether from mains electricity or a backup battery, to function effectively during emergencies. They are also typically fixed installations designed to remain in place and provide continuous monitoring, rather than being portable devices. Therefore, the presence of both auditory and visual alerts is crucial for effective communication during fire emergencies.