Electric Light - Types - Incandescent Light Bulb - Halogen Lamp

Halogen Lamp

Halogen lamps are usually much smaller than standard incandescents, because for successful operation a bulb temperature over 200 °C is generally necessary. For this reason, most have a bulb of fused silica (quartz), but sometimes aluminosilicate glass. This is often sealed inside an additional layer of glass. The outer glass is a safety precaution, reducing UV emission and because halogen bulbs can occasionally explode during operation. One reason is if the quartz bulb has oily residue from fingerprints. The risk of burns or fire is also greater with bare bulbs, leading to their prohibition in some places unless enclosed by the luminaire.

Those designed for 12 V or 24 V operation have compact filaments, useful for good optical control, also they have higher efficiencies (lumens per watt) and better lives than non halogen types. The light output remains almost constant throughout life.