Halogen light bulbs look and function much in the same way as incandescent light bulbs. They feature a glass bulb that contains an oxygen free environment. A tungsten filament is mounted in the center and the whole bulb is attached to a metal base that screws into a light fixture.
The key difference between other incandescent bulbs and a halogen bulb is that the bulb is filled with Halogen gas while incandescent bulbs are generally filled with argon gas. The halogen gas is contained in a small pressurized bulb that is encased in a larger outer glass bulb. In between the two layers of glass is krypton, which helps to slow down the evaporation of the tungsten; the tungsten evaporates due to the heat produced by the bulb. Incandescent bulbs last between 750 to 1,250 hours while halogen bulbs can last between 2,000 and 2,500 hours.
The halogen in the bulb reacts with the tungsten material that has flaked off of the filament. These tungsten particles cling to the inside of the glass but the halogen causes a chemical reaction that draws the tungsten back to the filament, which helps restore the filament's stability. The halogen also helps the bulb last longer by preserving the tungsten filament which, over time, becomes thinner and more fragile until it breaks.
Halogen bulbs come in a variety of shapes and sizes as well as wattage levels. They can be found in fixtures ranging from desk lamps to car lights and are sometimes housed within a protective casing to protect the bulb and filter out any UV rays. Some of these bulbs are also used in applications such as work spotlights with reflective fixtures to increase brightness.
In addition to a longer lifespan, halogen bulbs produce a different type of light than other bulbs. The filament must be heated to a higher temperature than filaments in non-gas containing bulbs in order for the chemical reaction between the tungsten and the gases to take place.
A result of this increased heat is a brighter and cleaner white light than the light of standard incandescent bulbs. Halogen bulbs are also more energy efficient because they produce more light per watt (measured in lumens). A 75-watt incandescent bulb produces 1,080 lumens while a 75-watt halogen bulb produces 1,300 lumens.
Halogen light bulbs can get extremely hot and so can be dangerous if touched. According to tests conducted by the New York State Consumer Protection Board, a high powered 300-watt halogen bulb can reach 970 degrees Fahrenheit. In comparison, a standard 75-watt incandescent bulb reaches only about 260 degrees Fahrenheit.
Another disadvantage is a slightly increased cost due to the extra glass needed to produce the bulbs. The high temperature combined with the chemical reaction requires glass that is thicker than that of regular incandescent bulbs.
It is also inadvisable to touch the bulb with your hands as oils from your skin can weaken the glass, increasing the risk that the bulb will burst once the filament burns out. These bulbs need to be used in safe locations away from flammable materials.