High Intensity Discharge or "HID" is the term commonly used to designate four
distinct types of lamps that actually have very little in common. They are
high pressure sodium, low pressure sodium, metal halide, and mercury vapor. Each
requires a few minutes (one to seven) to come up to full output. Also, if
power to the lamp is lost or turned off, the arc tube must cool to a given
temperature before the arc can be re-struck and light produced. Up to seven minutes
(for mercury vapor lamps) may be required.
For more detailed information . . .
