high-pressure sodium lamp
A high-pressure sodium lamp is a type of high-intensity discharge lamp that uses sodium under high pressure as the primary light-producing element. These high efficiency lights produce a golden white color and are used for interior industrial applications, such as in warehouses and manufacturing, and for security, street, and area lighting; they are becoming the most common type of outdoor lighting.
High-pressure sodium lamps have an efficacy of 50–140 lumens per watt – an efficiency exceeded only by low-pressure sodium lamps. Like mercury vapor lamps, high-pressure sodium lamps have a lower color rendition index than metal halide lamps but longer lifetimes (16,000–24,000 hours).