The plasma is able to supply large amounts of energy due to the energy changes associated with dissociating molecular gases to atomic gases and ionisation which occur with little change in temperature. These plasmas have higher energy contents for a given temperature than the atomic gases of argon and helium because of the energy associated with dissociation of molecules. These plasmas are relatively lower in energy content and higher in temperature than the plasmas from diatomic gases. Nitrogen is a general purpose primary gas used alone or with hydrogen secondary gas. Nitrogen also benefits from being the cheapest plasma gas.
Nitrogen tends to be inert to most spray material except materials like titanium.
Argon is the easiest of these gases to form a plasma and tends to less aggressive towards electrode and nozzle hardware. Most plasmas are started up using pure argon. Argon is a noble gas and is completely inert to all spray materials. Hydrogen is mainly used as a secondary gas, it dramatically effects heat transfer properties and acts as anti-oxidant. Small amounts of hydrogen added to the other plasma gases dramatically alters the plasma characteristics and energy levels and is thus used as one control for setting plasma voltage and energy.