Halogen bulbs are a variation of incandescent bulb technology. These bulbs work by passing electricity through a tungsten filament, which is enclosed in a tube containing halogen gas. This halogen gas causes a chemical reaction to take place which removes the tungsten from the wall of the glass and deposits it back onto the filament. This extends the life of the bulb. In order for the chemical reaction to take place, the filament needs to be hotter than what is needed for incandescent bulbs. The good news is that a hotter filament produces a brilliant white light and is more efficient (more lumens per watt).
The bad news is that a hotter filament means that the tungsten is evaporating that much faster. Therefore a denser, more expensive fill gas (krypton), and a higher pressure, are used to slow down the evaporation. This means that a thicker, but smaller glass bulb (envelope) is needed, which translates to a higher cost. Due to the smaller glass envelope (bulb), the halogen bulb gets much hotter than other bulbs. A 300 watt bulb can reach over 300 degrees C. Therefore attention must be paid to where halogen bulbs are used, so that they don’t accidentally come in contact with flammable materials, or burn those passing by.
Care must be taken not to touch the glass part of the bulb with our fingers. The oils from our fingers will weaken the glass and shorten the bulb’s life. Many times this causes the bulb to burst when the filament finally burns out.
To summarize, the halogen has the advantage of being more efficient (although not by much) and having longer life than the incandescent bulb. They are relatively small in size and are dimmable. The disadvantages are that they are more expensive, and burn at a much higher temperature, which could possibly be a fire hazard in certain areas.