Small leakage from the Discharge tube will result in a silver coating on the inside of the outer bulb or on the discharge tube itself.

When lamps are not replaced when due, the discharge tube may start leaking and can cause undesirable situations

This outer bulb is normally evacuated and the getter will absorb any contaminants.A leak in the discharge tube will allow gases such as sodium, krypton and xenon to enter the outer bulb, exhaust the getter and be precipitated on the inside of the outer glass. This will cause the temperature of the outer bulb to rise to as much as 800ºC.The glass could melt and deform or even become holed, causing immediate lamp breakdown.

Discharges in the outer bulb and short circuits could overload the ballast.A thermo-switch protects the ballast windings against high temperatures, and semi-parallel igniters are recommended because they are not part of the lamp circuit and are therefore not liable to damage