Excessive heat is the most common cause of Plasma tube failure. This type of damage happens when the glass wall of the plasma tube becomes so hot that oxygen gas and water vapor are released from the wall of the tube into the gas mixture. This results in contamination of the gas mixture inside the tube, causing an unwanted color shift in the ionized gas discharge and poor performance, sometimes resulting in amplifier failure.

The process of ionizing the gas in normal operation causes the glass wall of the tube directly under the electrodes to become very hot. Using ordinary bare copper or aluminum electrodes may result in damage to the tube wall due to overheating if high power is applied to the plasma tube. Damage may also result if the electrode area is too small for the power level being used. Due to their relatively poor emissivity, untreated copper or aluminum electrodes do not effectively remove excess heat from the plasma tube.