Abstract: A diluent injection burner apparatus capable of reducing the nitrogen oxide content in a combustion effluent, the diluent injection burner assembly provided with a burner head having an air flow passage extending therethrough and primary and secondary fuel dispensing nozzles supported within the airflow passageway and adapted to inject fuel into a downstream end portion of the burner head. A diluent manifold assembly is supported by the burner head such that upon combustion of the fuel diluent is tangentially injected into the downstream end portion of the burner head relative to a flame envelope produced by ignition of the primary and secondary fuel so that a diluent shroud is formed about a base portion of the flame envelope.