The
color temperature
of discharge lamps is reduced by approximately 1OK for each hour of continuous work. A
lamp
is considered 'dead' not when it stops working altogether but rather at the point at which output and intensity are reduced and the
color temperature
becomes unstable, resulting in poor color match between luminaires. For this reason, among others, manufacturers of discharge lamps recommend changing lamps after a specific number of hours of use. Another important consideration for limiting the number of working hours of a
lamp
is safety. Over a period of time changes occur in the glass
envelope
that weaken its resistance to the high pressure inside, making it a potentially dangerous object as it is apt to explode.
