Abstract This work presents an experimental investigation on the combustion behavior of a mixture of hydrogen, carbon monoxide and carbon dioxide in hot and diluted streams, like those obtain under flameless combustion regimes. A jet in a hot coflow burner was used to carry out the experiments. This burner consists of a central fuel jet surrounded by a combustion products stream, which comes from a premixed flame under lean conditions. In this way, it is possible to obtain high temperature and low oxygen concentration in the jet flame. Here, a mixture of 40% H 2 , 40% CO and 20% CO was issued through the jet nozzle. This composition corresponds to a renewable fuel known as syngas. Three oxygen composition in the oxidant stream were evaluated: 2.0%, 4.7% and 6.9%. Temperature and species concentration values were measured along axial and radial lines under a fix Reynolds’s number. The results suggest that when oxygen concentration increases, CO and NO emissions of the total process decreases.