Fluorescent lighting is a relatively low-energy form of lighting, using tubes containing mercury vapor and an internal phosphor coating. Electrically excited mercury vapor emits ultraviolet radiation, which stimulates the coating to produce visible light. It usually takes the form of long cylindrical tubes, normally mounted in the ceiling. It is used very commonly in dropped ceilings, but is also not uncommon as a hanging light installation.

If a building uses portable lighting appliances with compact fluorescent bulbs, then the applicable lighting system is plugged-in appliances. Only fixed fluorescent lighting installations fall under this category.

The fluorescent lamp produces visible light through its phosphor coating. That light-producing method is distinct from an incandescent filament, while the fixed-installation condition separates it from portable plug-in lamps.