Linear fluorescent lamps: T12, T8, T5
Although early forms of fluorescent lamp technology existed at the beginning of the 20th century, it wasn't considered a commercially viable light source until German inventor Edmund Germer filed a patent in 1926–1927. By the mid-1930s, engineers at General Electric were busy at work, and launched an entire research and development group dedicated to it. GE introduced a fluorescent lamp prototype at the 1939 World's Fair, and a new segment of the lighting industry was born overnight, producing a wave of luminaire and reflector design as well as ballast developments. As the lamp has been improved for performance and efficacy, its diameter has been reduced, opening up more possibilities for luminaire design and installation. Linear fluorescent lighting solutions have come to define commercial interiors and office spaces. Although legislation is now in place to eliminate the oldest of the fluorescent lamps—the T12—starting July 1, its forerunners—the T8, T5 and T5HO—remain some of the best performing and most cost-effective lighting options available.