Gas lamps were also common but had obvious disadvantages. Oil lamps with glass chimneys were the predecessors to electric lamps. Halogen lamps can also pose a safety threat, as the heat generated can range from 250-900☏ (121-482☌). These lamps can last up to 4,000 hours.Īlthough more efficient than other large incandescent lamps, tungsten halogen lamps are inefficient relative to fluorescent and high intensity discharge (HID) lamp types.

The filament burns hotter so less wattage is required. Some halogen lamps are also designed with a special infrared reflective coating on the outside of the bulb to ensure that the radiated heat, which otherwise is wasted, is reflected back to the lamp filament. Low voltage types range from 4-150 watts. Most halogen lamps range in power from 20-2,000 watts. They can last from 2,000-4,000 hours (about two to four years) compared to conventional incandescent bulbs, which only operate for 750-1,500 hours or three hours a day for about a year. Halogen bulbs thus produce light that is whiter and brighter, use less energy, and last longer than standard incandescent bulbs of the same wattage. This results in more energy leaving the filament by radiation, slightly improving the efficiency. Any use of premium fill gases also results in less heat being conducted from the filament by the fill gas. The higher pressure and better fill gases can extend the life of the bulb and/or permit a higher filament temperature that results in better efficiency. In addition, the small size of the bulb sometimes makes it economical to use heavier premium fill gases such as krypton or xenon-which help retard the rate of tungsten evaporation-instead of the cheaper argon. This slows down the evaporation of the tungsten from the filament, increasing the life of the lamp. Since the bulb is small and usually fairly strong due to its thicker walls, it can be filled with gas to a higher than usual pressure. This means that the bulb needs to be smaller and made of either quartz or a high-strength, heat-resistant grade of glass known as aluminosilicate. The halogen may not adequately vaporize or fail to adequately react with condensed tungsten if the bulb is too cool. In order for the halogen cycle to work, the bulb surface must be very hot, generally over 482☏ (250☌). This process-known as the tungsten-halogen cycle-maintains a constant light output over the life of the lamp. When the tungsten halide reaches the filament, the intense heat of the filament causes the halide to break down, releasing tungsten back to the filament. The halogen chemically reacts with the tungsten deposit to produce tungsten halides. The bulb, made of fused quartz instead of soda lime glass, is filled with the same inert gases as incandescent lamps mixed with small amounts of a halogen gas (usually less than 1% bromine). This blackening process continuously reduces the light out-put over the life of the lamp.Ī halogen lamp comes with a few modifications to eliminate this blackening problem. During operation, the tungsten evaporating from the hot filament condenses on the cooler inside bulb wall, causing the bulb to blacken.

When electrical power is applied to the filament, it becomes hot enough (generally over 3,600☏ ) to become incan-descent in other words, the filament glows and emits light. The conventional incandescent lamp contains a tungsten filament sealed within a glass envelope that is either evacuated or filled with an inert gas or a mixture of these gases (typically nitrogen, argon and krypton). A halogen lamp is a type of incandescent lamp.