Editing Metal-halide lamp (section)

===Risk of lamp explosion===
[[File:Exploded metal halide bulb.jpg|alt=Metal Halide Bulb Shattered|thumb|A metal halide bulb that has shattered as a result of an arc tube explosion due to uninterrupted prolonged use.]]
All metal halide arc tubes deteriorate in strength over their lifetime due to chemical attack, thermal stress and mechanical vibration. As the lamp ages the arc tube becomes discolored (often obtaining a dark grey shade), absorbing light and getting hotter. The tube will continue to become weaker until it eventually fails, causing the breakup of the tube.

Early failure of the arc tube may occur due to manufacturing defects. Manufacturers may "season" new lamps to check for such defects before sale.

Since a metal-halide lamp contains gases at a significant high pressure (up to 3.4 atmospheres), failure of the arc tube is inevitably a violent event. Fragments of arc tube will break the outer bulb, and hot glass fragments may fall on people or objects below. Hot fragments may present a fire hazard. Fixtures are designed to contain hot fragments with a hard glass cover, or may be designed for lamps with a quartz tube surrounding the arc tube to prevent breakage.

Shattering of the arc tube may be avoided by replacing the lamp if there is an excessive blackening of the arc tube, the arc tube begins to swell, there is a sudden changing of the light color, or the lamp begins to cycle on and off.