Gas discharge lamps are lighting appliances in which light is obtained by sending an electrical discharge through a gas. They are more energy efficient than conventional incandescent bulbs. However, they have the disadvantage that heavy metals are used in their manufacture, which means that once used they are also classified as hazardous waste.
The most well-known gas discharge lamps are fluorescent bulbs, which contain small amounts of mercury and which are used mainly in shops, offices and industry. They are, however, also used in the home, for example in bathrooms and kitchens. High-pressure mercury and sodium vapour discharge lamps are used for public lighting and in industrial buildings.