• Modern incandescent lights use inert gas to preserve the filament.light bulb image by Photosani from Fotolia.com
  
  Developed in the 19th century, incandescent lamps produce light by heating up a piece of metal, called a filament, until it glows. While modern incandescent lights come in many shapes and sizes, they all have the same basic elements. A tungsten filament is sealed inside a glass or quartz container and heated with electricity until it glows white hot. Most low-watt lights have the air removed, forming a vacuum. Lamps rated at 40 watts or above contain inert gas to preserve the filament.
  
  

Argon

• First discovered by Lord Rayleigh and Sir William Ramsay, argon is a tasteless, colorless and odorless gas that forms about 1 percent of the atmosphere. Argon, one of the inert or noble gases, doesn't react with other elements to form compounds. It also is used in neon signs and as a protective atmosphere for refining reactive elements, arc welding and growing crystals for superconductor devices.
  
  

Nitrogen

• Nitrogen, a colorless and odorless gas, forms about 78 percent of the atmosphere. Under normal circumstances, nitrogen doesn't burn or support combustion. A small amount of nitrogen is used in incandescent lamps to prevent arcing and sparks that are caused when electrical current jumps between the lead-in wires.
  
  

Krypton

• Another inert gas, krypton is a rare element found in the atmosphere in about one part per million. It increases the efficiency of incandescent lamps but is more expensive than argon. It also is used in fluorescent bulbs, photographic projection lamps, the arc lights used at airports and some electronic devices.