HALOGEN A form of incandescent lighting, halogen also uses tungsten filaments. But in halogen bulbs, the filaments are contained in a small glass capsule along with halogen gases, which trap evaporating tungsten and redeposit it on the filament, enabling halogen bulbs to last twice as long as traditional incandescent bulbs. This process makes halogens more efficient and also allows them to reach higher temperatures, thereby producing a whiter light.
One drawback is the toxicity of the mercury they contain, which means they should be disposed of properly or recycled. Ikea is among the few national retailers with a recycling program (the company accepts compact fluorescent bulbs purchased from any retailer and has bins in every store).
The Environmental Protection Agency is working to expand recycling and disposal options. There are a number of Web sites that offer information on using and disposing of the bulbs, including
L.E.D. Light-emitting diodes are semiconductor chips that produce light when electrified. They have been used for years in electronic gadgets and in traffic signals. But it is only recently that they have begun appearing in residential lighting, as advances in technology have resulted in diodes that emit white rather than colored light.
L.E.D.s consume about the same electricity used by fluorescent bulbs and can last significantly longer, but they remain costly. They do not produce much heat or contain mercury. They cast light in a single direction and are best suited to reading lamps, strip lighting (the kind used under kitchen cabinets) and night lights.