HID lamp wear and aging is discoloration of the emitted light beam ("fading"). Commonly, a shift towards blue and/or violet can be observed. This shift is slight at first and is more generally a sign of the lamps being "broken in" whilst still being in good overall working order, but towards the end of its life, the HID lamp is often perceived as only producing blue and violet light. Based on Planck's law, this is a direct result of the increased voltage and higher temperature necessary to maintain the arc. Sometimes the quartz tube containing mercury can explode in a UHP lamp. When that happens, up to 50 mg of mercury vapor is released into the atmosphere. This quantity of mercury is potentially toxic, but the main hazard from broken lamps is glass cuts, and occasional exposure to broken lamps is not expected to have adverse effects. Philips recommends the use of a mercury vacuum cleaner, ventilation or respiratory protection, eye protection, and protective clothing when dealing with broken lamps. Mercury lamps always require specialised disposal or recycling, which is legally mandatory in many locations depending on jurisdiction. References Gas discharge lamps Automotive lamps de:Gasentladungsröhre#Hochdruck-Entladungslampen (HID-Lampen) ru:Газоразрядная лампа