Incandescent light bulb granted a Hungarian patent (No. 34541) for a tungsten filament lamp that lasted longer and gave brighter light than the carbon filament. Tungsten filament lamps were first marketed by the Hungarian company Tungsram in 1904. This type is often called Tungsram-bulbs in many European countries. Filling a bulb with an inert gas such as argon or nitrogen slows down the evaporation of the tungsten filament compared to operating it in a vacuum. This allows for greater temperatures and therefore greater efficacy with less reduction in filament life. In 1906, William D. Coolidge developed a method of making "ductile tungsten" from
Phase-out of incandescent light bulbs mercury contamination from CFLs have been raised, but CFLs can be shown to result in less mercury in the environment compared to traditional incandescent bulbs due to the significant reductions in power plant emissions. Thus, use of energy-efficient bulbs can actually reduce the amount of mercury released into the environment. Compact fluorescent lamps start poorly when very cold, and most types cannot be dimmed. A few specialist applications are unsuitable for CFLs. Light emitting diode (LED) lamps are used for both general and special-purpose lighting. Compared to fluorescent bulbs, their advantages are that they contain no mercury, they turn on