Tungsten is used in many different types of incandescent lamps. The most common types are the general household lamps (GLS lamps), automotive lamps, reflector lamps for floodlight or projector applications. There are also many thousands of speciality lamps, which have a broad range of applications, such as audio-visual projectors, fibre-optical systems, video camera lights, airport runway markers, photo printers, medical and scientific instruments, and stage or studio systems. Wire diameters are in the range of 15 to 50μm, but can be as low as 6μm or as high as 1mm. Power ratings are from a few watts to several thousand watts (lighthouse lamps; up to 10 kW).
Large bulbs are used for conventional incandescent lamps to spread the evaporating tungsten over a large area in order to minimize wall blackening. Operating temperatures are between 1,700 and 2,500°C. Incandescent bulbs (GLS lamps) have a maximum efficacy of 15 lm/W only (ie they produce significantly more heat than light during use) at a burning life of 1,000h.
Halogen lamps are used more and more for indoor and outdoor applications due to their higher luminous efficiency as compared to conventional lamps (max efficacy: 27 lm/W). Bulb wall blackening is avoided by the addition of halogen compounds (commonly mono-, di-, or tribromomethane) and a higher inert gas pressure. They can be operated at higher temperatures (up to 3,000°C) and have a lifespan of about 2,000h.
Modern halogen lamps have an Infra Red Coating (IRC) and are 30% more economical than standard halogen lamps.