Lean Exo-gas is produced by burning of fuels at slightly lower sub-stoichiometric combustion air to fuel ratio. This Exo-gas is lean in CO + H2 content. Lean Exo-gas generators are suitable for non-ferrous metals heat treatment.
Rich Exo-gas is produced by burning of fuel at high sub-stoichoimetric combustion of air to fuel ratio. So the Exo-gas produced is rich in CO + H2 content. Rich Exo-gas generators are used for heat treatment of steel and also brazing and annealing applications.