What are High Intensity Discharge (HID) lamps?
There are two main types of HID lamps commonly used as supplementary lighting in either a grow-room or greenhouse. They are Metal Halide (MH) lamps and High Pressure Sodium (HPS) Lamps. Both of these lamp types require the use of an external control gear (ballast) to be ignited. HID lamps were most commonly used for street and warehouse lighting but they have been adapted for horticultural use, particularly in environments where natural sunlight is insufficient.
