Low-pressure sodium lamps are a type of gas discharge lamp that produce light through the excitation of sodium vapor. They operate at low pressure, which allows them to be highly efficient and long-lasting. These lamps emit a characteristic yellow-orange light, making them easily recognizable. They are commonly used for street lighting and outdoor applications due to their energy efficiency and ability to penetrate fog and rain. The design of low-pressure sodium lamps includes a glass tube filled with sodium and a small amount of neon or argon gas. When electricity passes through the gas, it ionizes and heats the sodium, causing it to emit light. Despite their efficiency, the monochromatic light produced limits color recognition, which is a consideration in their use.