What is a fundamental requirement for exit sign luminaires?

The fundamental requirement for exit sign luminaires is that they must be illuminated and meet visibility guidelines. This ensures that in case of an emergency, individuals can easily identify the route to safety. Exit signs are critical components in building safety, guiding occupants toward exits even in low-light conditions or when visibility is compromised.

Illuminated exit signs are mandated to be clearly visible from a distance and must be designed to provide sufficient illumination to avoid confusion in emergency situations. This visibility must comply with specific height and contrast ratios as established by relevant codes, ensuring they are effective for everyone, including individuals with disabilities.

In contrast to other options, which might suggest certain conditions or preferences, the requirement for illumination ensures that exit signs consistently fulfill their purpose of guiding people safely out of a building.